Mercurial > hg > octave-kai > gnulib-hg
annotate doc/standards.texi @ 17454:9b8de09b2e2e
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| author | Karl Berry <karl@freefriends.org> |
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| date | Fri, 19 Jul 2013 15:08:53 -0700 |
| parents | 8826dc2ee3ee |
| children | 09c1c72dfe80 |
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1 \input texinfo @c -*-texinfo-*- |
| 4958 | 2 @c %**start of header |
| 3 @setfilename standards.info | |
| 4 @settitle GNU Coding Standards | |
| 5 @c This date is automagically updated when you save this file: | |
| 17454 | 6 @set lastupdate July 19, 2013 |
| 4958 | 7 @c %**end of header |
| 8 | |
| 9 @dircategory GNU organization | |
| 10 @direntry | |
|
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11 * Standards: (standards). GNU coding standards. |
| 4958 | 12 @end direntry |
| 13 | |
| 14 @c @setchapternewpage odd | |
| 15 @setchapternewpage off | |
| 16 | |
| 17 @c Put everything in one index (arbitrarily chosen to be the concept index). | |
| 18 @syncodeindex fn cp | |
| 19 @syncodeindex ky cp | |
| 20 @syncodeindex pg cp | |
| 21 @syncodeindex vr cp | |
| 22 | |
| 23 @c This is used by a cross ref in make-stds.texi | |
| 24 @set CODESTD 1 | |
| 25 | |
| 26 @copying | |
| 27 The GNU coding standards, last updated @value{lastupdate}. | |
| 28 | |
| 7910 | 29 Copyright @copyright{} 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, |
| 16279 | 30 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, |
| 17256 | 31 2011, 2012, 2013 Free Software Foundation, Inc. |
| 4958 | 32 |
| 33 Permission is granted to copy, distribute and/or modify this document | |
| 10774 | 34 under the terms of the GNU Free Documentation License, Version 1.3 or |
| 35 any later version published by the Free Software Foundation; with no | |
| 36 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover | |
| 37 Texts. A copy of the license is included in the section entitled | |
| 38 ``GNU Free Documentation License''. | |
| 4958 | 39 @end copying |
| 40 | |
| 41 @titlepage | |
| 42 @title GNU Coding Standards | |
| 43 @author Richard Stallman, et al. | |
| 44 @author last updated @value{lastupdate} | |
| 45 @page | |
| 46 @vskip 0pt plus 1filll | |
| 47 @insertcopying | |
| 48 @end titlepage | |
| 49 | |
| 50 @contents | |
| 51 | |
| 52 @ifnottex | |
| 14502 | 53 @node Top |
| 54 @top GNU Coding Standards | |
| 4958 | 55 |
| 56 @insertcopying | |
| 57 @end ifnottex | |
| 58 | |
| 59 @menu | |
| 9115 | 60 * Preface:: About the GNU Coding Standards. |
| 61 * Legal Issues:: Keeping free software free. | |
| 62 * Design Advice:: General program design. | |
| 63 * Program Behavior:: Program behavior for all programs | |
| 64 * Writing C:: Making the best use of C. | |
| 65 * Documentation:: Documenting programs. | |
| 66 * Managing Releases:: The release process. | |
| 67 * References:: Mentioning non-free software or documentation. | |
| 68 * GNU Free Documentation License:: Copying and sharing this manual. | |
| 6725 | 69 * Index:: |
| 4958 | 70 |
| 71 @end menu | |
| 72 | |
| 73 @node Preface | |
| 74 @chapter About the GNU Coding Standards | |
| 75 | |
| 76 The GNU Coding Standards were written by Richard Stallman and other GNU | |
| 77 Project volunteers. Their purpose is to make the GNU system clean, | |
| 78 consistent, and easy to install. This document can also be read as a | |
| 79 guide to writing portable, robust and reliable programs. It focuses on | |
| 80 programs written in C, but many of the rules and principles are useful | |
| 81 even if you write in another programming language. The rules often | |
| 82 state reasons for writing in a certain way. | |
| 83 | |
| 84 @cindex where to obtain @code{standards.texi} | |
| 85 @cindex downloading this manual | |
| 86 If you did not obtain this file directly from the GNU project and | |
| 87 recently, please check for a newer version. You can get the GNU | |
| 5301 | 88 Coding Standards from the GNU web server in many |
| 89 different formats, including the Texinfo source, PDF, HTML, DVI, plain | |
| 90 text, and more, at: @uref{http://www.gnu.org/prep/standards/}. | |
| 4958 | 91 |
| 12332 | 92 If you are maintaining an official GNU package, in addition to this |
| 93 document, please read and follow the GNU maintainer information | |
| 94 (@pxref{Top, , Contents, maintain, Information for Maintainers of GNU | |
| 95 Software}). | |
| 96 | |
| 97 @cindex @code{gnustandards-commit@@gnu.org} mailing list | |
| 98 If you want to receive diffs for every change to these GNU documents, | |
| 99 join the mailing list @code{gnustandards-commit@@gnu.org}, via the web | |
| 100 interface at | |
| 101 @url{http://lists.gnu.org/mailman/listinfo/gnustandards-commit}. | |
| 102 Archives are also available there. | |
| 103 | |
| 13056 | 104 @cindex @code{bug-standards@@gnu.org} email address |
| 105 @cindex Savannah repository for gnustandards | |
| 13057 | 106 @cindex gnustandards project repository |
| 13049 | 107 Please send corrections or suggestions for this document to |
| 108 @email{bug-standards@@gnu.org}. If you make a suggestion, please | |
| 109 include a suggested new wording for it, to help us consider the | |
| 110 suggestion efficiently. We prefer a context diff to the Texinfo | |
| 111 source, but if that's difficult for you, you can make a context diff | |
| 112 for some other version of this document, or propose it in any way that | |
| 113 makes it clear. The source repository for this document can be found | |
| 114 at @url{http://savannah.gnu.org/projects/gnustandards}. | |
| 4958 | 115 |
| 116 These standards cover the minimum of what is important when writing a | |
| 8453 | 117 GNU package. Likely, the need for additional standards will come up. |
| 4958 | 118 Sometimes, you might suggest that such standards be added to this |
| 119 document. If you think your standards would be generally useful, please | |
| 120 do suggest them. | |
| 121 | |
| 122 You should also set standards for your package on many questions not | |
| 123 addressed or not firmly specified here. The most important point is to | |
| 124 be self-consistent---try to stick to the conventions you pick, and try | |
| 125 to document them as much as possible. That way, your program will be | |
| 126 more maintainable by others. | |
| 127 | |
| 128 The GNU Hello program serves as an example of how to follow the GNU | |
| 6725 | 129 coding standards for a trivial program. |
| 130 @uref{http://www.gnu.org/software/hello/hello.html}. | |
| 4958 | 131 |
| 12332 | 132 This release of the GNU Coding Standards was last updated |
| 133 @value{lastupdate}. | |
| 134 | |
| 135 | |
| 4958 | 136 @node Legal Issues |
| 137 @chapter Keeping Free Software Free | |
| 138 @cindex legal aspects | |
| 139 | |
| 5301 | 140 This chapter discusses how you can make sure that GNU software |
| 4958 | 141 avoids legal difficulties, and other related issues. |
| 142 | |
| 143 @menu | |
| 9115 | 144 * Reading Non-Free Code:: Referring to proprietary programs. |
| 145 * Contributions:: Accepting contributions. | |
| 146 * Trademarks:: How we deal with trademark issues. | |
| 4958 | 147 @end menu |
| 148 | |
| 149 @node Reading Non-Free Code | |
| 150 @section Referring to Proprietary Programs | |
| 151 @cindex proprietary programs | |
| 152 @cindex avoiding proprietary code | |
| 153 | |
| 154 Don't in any circumstances refer to Unix source code for or during | |
| 155 your work on GNU! (Or to any other proprietary programs.) | |
| 156 | |
| 157 If you have a vague recollection of the internals of a Unix program, | |
| 158 this does not absolutely mean you can't write an imitation of it, but | |
| 159 do try to organize the imitation internally along different lines, | |
| 160 because this is likely to make the details of the Unix version | |
| 161 irrelevant and dissimilar to your results. | |
| 162 | |
| 163 For example, Unix utilities were generally optimized to minimize | |
| 164 memory use; if you go for speed instead, your program will be very | |
| 7663 | 165 different. You could keep the entire input file in memory and scan it |
| 4958 | 166 there instead of using stdio. Use a smarter algorithm discovered more |
| 167 recently than the Unix program. Eliminate use of temporary files. Do | |
| 168 it in one pass instead of two (we did this in the assembler). | |
| 169 | |
| 170 Or, on the contrary, emphasize simplicity instead of speed. For some | |
| 171 applications, the speed of today's computers makes simpler algorithms | |
| 172 adequate. | |
| 173 | |
| 174 Or go for generality. For example, Unix programs often have static | |
| 175 tables or fixed-size strings, which make for arbitrary limits; use | |
| 176 dynamic allocation instead. Make sure your program handles NULs and | |
| 177 other funny characters in the input files. Add a programming language | |
| 178 for extensibility and write part of the program in that language. | |
| 179 | |
| 180 Or turn some parts of the program into independently usable libraries. | |
| 181 Or use a simple garbage collector instead of tracking precisely when | |
| 182 to free memory, or use a new GNU facility such as obstacks. | |
| 183 | |
| 14719 | 184 |
| 4958 | 185 @node Contributions |
| 186 @section Accepting Contributions | |
| 187 @cindex legal papers | |
| 188 @cindex accepting contributions | |
| 189 | |
| 190 If the program you are working on is copyrighted by the Free Software | |
| 191 Foundation, then when someone else sends you a piece of code to add to | |
| 192 the program, we need legal papers to use it---just as we asked you to | |
| 193 sign papers initially. @emph{Each} person who makes a nontrivial | |
| 194 contribution to a program must sign some sort of legal papers in order | |
| 195 for us to have clear title to the program; the main author alone is not | |
| 196 enough. | |
| 197 | |
| 198 So, before adding in any contributions from other people, please tell | |
| 199 us, so we can arrange to get the papers. Then wait until we tell you | |
| 200 that we have received the signed papers, before you actually use the | |
| 201 contribution. | |
| 202 | |
| 203 This applies both before you release the program and afterward. If | |
| 204 you receive diffs to fix a bug, and they make significant changes, we | |
| 205 need legal papers for that change. | |
| 206 | |
| 207 This also applies to comments and documentation files. For copyright | |
| 208 law, comments and code are just text. Copyright applies to all kinds of | |
| 209 text, so we need legal papers for all kinds. | |
| 210 | |
| 211 We know it is frustrating to ask for legal papers; it's frustrating for | |
| 212 us as well. But if you don't wait, you are going out on a limb---for | |
| 213 example, what if the contributor's employer won't sign a disclaimer? | |
| 214 You might have to take that code out again! | |
| 215 | |
| 216 You don't need papers for changes of a few lines here or there, since | |
| 217 they are not significant for copyright purposes. Also, you don't need | |
| 218 papers if all you get from the suggestion is some ideas, not actual code | |
| 5301 | 219 which you use. For example, if someone sent you one implementation, but |
| 4958 | 220 you write a different implementation of the same idea, you don't need to |
| 221 get papers. | |
| 222 | |
| 223 The very worst thing is if you forget to tell us about the other | |
| 224 contributor. We could be very embarrassed in court some day as a | |
| 225 result. | |
| 226 | |
| 14719 | 227 We have more detailed advice for maintainers of GNU packages. If you |
| 228 have reached the stage of maintaining a GNU program (whether released | |
| 229 or not), please take a look: @pxref{Legal Matters,,, maintain, | |
| 230 Information for GNU Maintainers}. | |
| 231 | |
| 4958 | 232 |
| 233 @node Trademarks | |
| 234 @section Trademarks | |
| 235 @cindex trademarks | |
| 236 | |
| 237 Please do not include any trademark acknowledgements in GNU software | |
| 238 packages or documentation. | |
| 239 | |
| 240 Trademark acknowledgements are the statements that such-and-such is a | |
| 241 trademark of so-and-so. The GNU Project has no objection to the basic | |
| 6725 | 242 idea of trademarks, but these acknowledgements feel like kowtowing, |
| 4958 | 243 and there is no legal requirement for them, so we don't use them. |
| 244 | |
| 245 What is legally required, as regards other people's trademarks, is to | |
| 246 avoid using them in ways which a reader might reasonably understand as | |
| 247 naming or labeling our own programs or activities. For example, since | |
| 248 ``Objective C'' is (or at least was) a trademark, we made sure to say | |
| 249 that we provide a ``compiler for the Objective C language'' rather | |
| 250 than an ``Objective C compiler''. The latter would have been meant as | |
| 251 a shorter way of saying the former, but it does not explicitly state | |
| 252 the relationship, so it could be misinterpreted as using ``Objective | |
| 253 C'' as a label for the compiler rather than for the language. | |
| 254 | |
| 255 Please don't use ``win'' as an abbreviation for Microsoft Windows in | |
| 256 GNU software or documentation. In hacker terminology, calling | |
| 5909 | 257 something a ``win'' is a form of praise. If you wish to praise |
| 4958 | 258 Microsoft Windows when speaking on your own, by all means do so, but |
| 5909 | 259 not in GNU software. Usually we write the name ``Windows'' in full, |
| 4958 | 260 but when brevity is very important (as in file names and sometimes |
| 261 symbol names), we abbreviate it to ``w''. For instance, the files and | |
| 262 functions in Emacs that deal with Windows start with @samp{w32}. | |
| 263 | |
| 264 @node Design Advice | |
| 265 @chapter General Program Design | |
| 266 @cindex program design | |
| 267 | |
| 5301 | 268 This chapter discusses some of the issues you should take into |
| 4958 | 269 account when designing your program. |
| 270 | |
| 271 @c Standard or ANSI C | |
| 272 @c | |
| 273 @c In 1989 the American National Standards Institute (ANSI) standardized | |
| 274 @c C as standard X3.159-1989. In December of that year the | |
| 275 @c International Standards Organization ISO adopted the ANSI C standard | |
| 276 @c making minor changes. In 1990 ANSI then re-adopted ISO standard | |
| 277 @c C. This version of C is known as either ANSI C or Standard C. | |
| 278 | |
| 279 @c A major revision of the C Standard appeared in 1999. | |
| 280 | |
| 281 @menu | |
|
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282 * Source Language:: Which languages to use. |
| 9115 | 283 * Compatibility:: Compatibility with other implementations. |
| 284 * Using Extensions:: Using non-standard features. | |
| 285 * Standard C:: Using standard C features. | |
| 286 * Conditional Compilation:: Compiling code only if a conditional is true. | |
| 4958 | 287 @end menu |
| 288 | |
| 289 @node Source Language | |
| 290 @section Which Languages to Use | |
|
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291 @cindex programming languages |
| 4958 | 292 |
| 293 When you want to use a language that gets compiled and runs at high | |
| 17454 | 294 speed, the best language to use is C. C++ is ok too, but please don't |
| 295 make heavy use of templates. Other languages commonly used in the | |
| 296 free software community, such as Java, Python and Ruby, are ok too. | |
| 297 Please implement the GNU configure and make interface no matter which | |
| 298 language you use. | |
| 4958 | 299 |
| 300 Many programs are designed to be extensible: they include an interpreter | |
| 301 for a language that is higher level than C. Often much of the program | |
| 302 is written in that language, too. The Emacs editor pioneered this | |
| 303 technique. | |
| 304 | |
| 10037 | 305 @cindex Guile |
| 306 @cindex GNOME and Guile | |
| 307 The standard extensibility interpreter for GNU software is Guile | |
| 9823 | 308 (@uref{http://www.gnu.org/@/software/@/guile/}), which implements the |
| 10037 | 309 language Scheme (an especially clean and simple dialect of Lisp). |
| 310 Guile also includes bindings for GTK+/GNOME, making it practical to | |
| 311 write modern GUI functionality within Guile. We don't reject programs | |
| 312 written in other ``scripting languages'' such as Perl and Python, but | |
| 17454 | 313 using Guile is the path that will lead to overall consistency of the |
| 314 GNU system. | |
| 10037 | 315 |
| 4958 | 316 |
| 317 @node Compatibility | |
| 318 @section Compatibility with Other Implementations | |
| 17256 | 319 @cindex compatibility with C and POSIX standards |
| 320 @cindex C compatibility | |
| 321 @cindex POSIX compatibility | |
| 4958 | 322 |
| 323 With occasional exceptions, utility programs and libraries for GNU | |
| 324 should be upward compatible with those in Berkeley Unix, and upward | |
| 325 compatible with Standard C if Standard C specifies their | |
| 17256 | 326 behavior, and upward compatible with POSIX if POSIX specifies |
| 4958 | 327 their behavior. |
| 328 | |
| 329 When these standards conflict, it is useful to offer compatibility | |
| 330 modes for each of them. | |
| 331 | |
| 332 @cindex options for compatibility | |
| 17256 | 333 Standard C and POSIX prohibit many kinds of extensions. Feel |
| 4958 | 334 free to make the extensions anyway, and include a @samp{--ansi}, |
| 335 @samp{--posix}, or @samp{--compatible} option to turn them off. | |
| 336 However, if the extension has a significant chance of breaking any real | |
| 337 programs or scripts, then it is not really upward compatible. So you | |
| 338 should try to redesign its interface to make it upward compatible. | |
| 339 | |
| 340 @cindex @code{POSIXLY_CORRECT}, environment variable | |
| 17256 | 341 Many GNU programs suppress extensions that conflict with POSIX if the |
| 4958 | 342 environment variable @code{POSIXLY_CORRECT} is defined (even if it is |
| 343 defined with a null value). Please make your program recognize this | |
| 344 variable if appropriate. | |
| 345 | |
| 346 When a feature is used only by users (not by programs or command | |
| 347 files), and it is done poorly in Unix, feel free to replace it | |
| 348 completely with something totally different and better. (For example, | |
| 349 @code{vi} is replaced with Emacs.) But it is nice to offer a compatible | |
| 350 feature as well. (There is a free @code{vi} clone, so we offer it.) | |
| 351 | |
| 352 Additional useful features are welcome regardless of whether | |
| 353 there is any precedent for them. | |
| 354 | |
| 355 @node Using Extensions | |
| 356 @section Using Non-standard Features | |
| 357 @cindex non-standard extensions | |
| 358 | |
| 359 Many GNU facilities that already exist support a number of convenient | |
| 360 extensions over the comparable Unix facilities. Whether to use these | |
| 361 extensions in implementing your program is a difficult question. | |
| 362 | |
| 363 On the one hand, using the extensions can make a cleaner program. | |
| 364 On the other hand, people will not be able to build the program | |
| 365 unless the other GNU tools are available. This might cause the | |
| 366 program to work on fewer kinds of machines. | |
| 367 | |
| 368 With some extensions, it might be easy to provide both alternatives. | |
| 369 For example, you can define functions with a ``keyword'' @code{INLINE} | |
| 370 and define that as a macro to expand into either @code{inline} or | |
| 371 nothing, depending on the compiler. | |
| 372 | |
| 373 In general, perhaps it is best not to use the extensions if you can | |
| 374 straightforwardly do without them, but to use the extensions if they | |
| 375 are a big improvement. | |
| 376 | |
| 377 An exception to this rule are the large, established programs (such as | |
| 378 Emacs) which run on a great variety of systems. Using GNU extensions in | |
| 379 such programs would make many users unhappy, so we don't do that. | |
| 380 | |
| 381 Another exception is for programs that are used as part of compilation: | |
| 382 anything that must be compiled with other compilers in order to | |
| 383 bootstrap the GNU compilation facilities. If these require the GNU | |
| 384 compiler, then no one can compile them without having them installed | |
| 385 already. That would be extremely troublesome in certain cases. | |
| 386 | |
| 387 @node Standard C | |
| 388 @section Standard C and Pre-Standard C | |
| 17256 | 389 @cindex ANSI C standard |
| 4958 | 390 |
| 391 1989 Standard C is widespread enough now that it is ok to use its | |
| 17256 | 392 features in programs. There is one exception: do not ever use the |
| 4958 | 393 ``trigraph'' feature of Standard C. |
| 394 | |
| 17256 | 395 The 1999 and 2011 editions of Standard C are not fully supported |
| 396 on all platforms. If you aim to support compilation by | |
| 397 compilers other than GCC, you should not require these C | |
| 398 features in your programs. It is ok to use these features | |
| 399 conditionally when the compiler supports them. | |
| 400 | |
| 401 If your program is only meant to compile with GCC, then you can | |
| 402 use these features if GCC supports them, when they give substantial | |
| 403 benefit. | |
| 4958 | 404 |
| 405 However, it is easy to support pre-standard compilers in most programs, | |
| 17256 | 406 so if you know how to do that, feel free. |
| 4958 | 407 |
| 408 @cindex function prototypes | |
| 409 To support pre-standard C, instead of writing function definitions in | |
| 410 standard prototype form, | |
| 411 | |
| 412 @example | |
| 413 int | |
| 414 foo (int x, int y) | |
| 415 @dots{} | |
| 416 @end example | |
| 417 | |
| 418 @noindent | |
| 419 write the definition in pre-standard style like this, | |
| 420 | |
| 421 @example | |
| 422 int | |
| 423 foo (x, y) | |
| 424 int x, y; | |
| 425 @dots{} | |
| 426 @end example | |
| 427 | |
| 428 @noindent | |
| 429 and use a separate declaration to specify the argument prototype: | |
| 430 | |
| 431 @example | |
| 432 int foo (int, int); | |
| 433 @end example | |
| 434 | |
| 435 You need such a declaration anyway, in a header file, to get the benefit | |
| 436 of prototypes in all the files where the function is called. And once | |
| 437 you have the declaration, you normally lose nothing by writing the | |
| 438 function definition in the pre-standard style. | |
| 439 | |
| 440 This technique does not work for integer types narrower than @code{int}. | |
| 441 If you think of an argument as being of a type narrower than @code{int}, | |
| 442 declare it as @code{int} instead. | |
| 443 | |
| 444 There are a few special cases where this technique is hard to use. For | |
| 445 example, if a function argument needs to hold the system type | |
| 446 @code{dev_t}, you run into trouble, because @code{dev_t} is shorter than | |
| 447 @code{int} on some machines; but you cannot use @code{int} instead, | |
| 448 because @code{dev_t} is wider than @code{int} on some machines. There | |
| 449 is no type you can safely use on all machines in a non-standard | |
| 450 definition. The only way to support non-standard C and pass such an | |
| 451 argument is to check the width of @code{dev_t} using Autoconf and choose | |
| 452 the argument type accordingly. This may not be worth the trouble. | |
| 453 | |
| 454 In order to support pre-standard compilers that do not recognize | |
| 455 prototypes, you may want to use a preprocessor macro like this: | |
| 456 | |
| 457 @example | |
| 458 /* Declare the prototype for a general external function. */ | |
| 459 #if defined (__STDC__) || defined (WINDOWSNT) | |
| 460 #define P_(proto) proto | |
| 461 #else | |
| 462 #define P_(proto) () | |
| 463 #endif | |
| 464 @end example | |
| 465 | |
| 466 @node Conditional Compilation | |
| 467 @section Conditional Compilation | |
| 468 | |
| 469 When supporting configuration options already known when building your | |
| 470 program we prefer using @code{if (... )} over conditional compilation, | |
| 471 as in the former case the compiler is able to perform more extensive | |
| 472 checking of all possible code paths. | |
| 473 | |
| 474 For example, please write | |
| 475 | |
| 476 @smallexample | |
| 477 if (HAS_FOO) | |
| 478 ... | |
| 479 else | |
| 480 ... | |
| 481 @end smallexample | |
| 482 | |
| 483 @noindent | |
| 484 instead of: | |
| 485 | |
| 486 @smallexample | |
| 487 #ifdef HAS_FOO | |
| 488 ... | |
| 489 #else | |
| 490 ... | |
| 491 #endif | |
| 492 @end smallexample | |
| 493 | |
| 494 A modern compiler such as GCC will generate exactly the same code in | |
| 495 both cases, and we have been using similar techniques with good success | |
| 496 in several projects. Of course, the former method assumes that | |
| 497 @code{HAS_FOO} is defined as either 0 or 1. | |
| 498 | |
| 499 While this is not a silver bullet solving all portability problems, | |
| 500 and is not always appropriate, following this policy would have saved | |
| 501 GCC developers many hours, or even days, per year. | |
| 502 | |
| 503 In the case of function-like macros like @code{REVERSIBLE_CC_MODE} in | |
| 12897 | 504 GCC which cannot be simply used in @code{if (...)} statements, there is |
| 4958 | 505 an easy workaround. Simply introduce another macro |
| 506 @code{HAS_REVERSIBLE_CC_MODE} as in the following example: | |
| 507 | |
| 508 @smallexample | |
| 509 #ifdef REVERSIBLE_CC_MODE | |
| 510 #define HAS_REVERSIBLE_CC_MODE 1 | |
| 511 #else | |
| 512 #define HAS_REVERSIBLE_CC_MODE 0 | |
| 513 #endif | |
| 514 @end smallexample | |
| 515 | |
| 516 @node Program Behavior | |
| 517 @chapter Program Behavior for All Programs | |
| 518 | |
| 5301 | 519 This chapter describes conventions for writing robust |
| 4958 | 520 software. It also describes general standards for error messages, the |
| 521 command line interface, and how libraries should behave. | |
| 522 | |
| 523 @menu | |
| 6629 | 524 * Non-GNU Standards:: We consider standards such as POSIX; |
| 525 we don't "obey" them. | |
| 9115 | 526 * Semantics:: Writing robust programs. |
| 527 * Libraries:: Library behavior. | |
| 528 * Errors:: Formatting error messages. | |
| 529 * User Interfaces:: Standards about interfaces generally. | |
| 530 * Graphical Interfaces:: Standards for graphical interfaces. | |
| 531 * Command-Line Interfaces:: Standards for command line interfaces. | |
| 13575 | 532 * Dynamic Plug-In Interfaces:: Standards for dynamic plug-in interfaces. |
| 9115 | 533 * Option Table:: Table of long options. |
| 10742 | 534 * OID Allocations:: Table of OID slots for GNU. |
| 9115 | 535 * Memory Usage:: When and how to care about memory needs. |
| 536 * File Usage:: Which files to use, and where. | |
| 4958 | 537 @end menu |
| 538 | |
| 6629 | 539 @node Non-GNU Standards |
| 540 @section Non-GNU Standards | |
| 541 | |
| 542 The GNU Project regards standards published by other organizations as | |
| 543 suggestions, not orders. We consider those standards, but we do not | |
| 544 ``obey'' them. In developing a GNU program, you should implement | |
| 545 an outside standard's specifications when that makes the GNU system | |
| 546 better overall in an objective sense. When it doesn't, you shouldn't. | |
| 547 | |
| 548 In most cases, following published standards is convenient for | |
| 549 users---it means that their programs or scripts will work more | |
| 550 portably. For instance, GCC implements nearly all the features of | |
| 551 Standard C as specified by that standard. C program developers would | |
| 552 be unhappy if it did not. And GNU utilities mostly follow | |
| 553 specifications of POSIX.2; shell script writers and users would be | |
| 554 unhappy if our programs were incompatible. | |
| 555 | |
| 556 But we do not follow either of these specifications rigidly, and there | |
| 557 are specific points on which we decided not to follow them, so as to | |
| 558 make the GNU system better for users. | |
| 559 | |
| 560 For instance, Standard C says that nearly all extensions to C are | |
| 561 prohibited. How silly! GCC implements many extensions, some of which | |
| 562 were later adopted as part of the standard. If you want these | |
| 563 constructs to give an error message as ``required'' by the standard, | |
| 564 you must specify @samp{--pedantic}, which was implemented only so that | |
| 15793 | 565 we can say ``GCC is a 100% implementation of the standard'', not |
| 6629 | 566 because there is any reason to actually use it. |
| 567 | |
| 568 POSIX.2 specifies that @samp{df} and @samp{du} must output sizes by | |
| 569 default in units of 512 bytes. What users want is units of 1k, so | |
| 570 that is what we do by default. If you want the ridiculous behavior | |
| 571 ``required'' by POSIX, you must set the environment variable | |
| 572 @samp{POSIXLY_CORRECT} (which was originally going to be named | |
| 573 @samp{POSIX_ME_HARDER}). | |
| 574 | |
| 575 GNU utilities also depart from the letter of the POSIX.2 specification | |
| 576 when they support long-named command-line options, and intermixing | |
| 577 options with ordinary arguments. This minor incompatibility with | |
| 578 POSIX is never a problem in practice, and it is very useful. | |
| 579 | |
| 580 In particular, don't reject a new feature, or remove an old one, | |
| 15793 | 581 merely because a standard says it is ``forbidden'' or ``deprecated''. |
| 6629 | 582 |
| 14719 | 583 |
| 4958 | 584 @node Semantics |
| 585 @section Writing Robust Programs | |
| 586 | |
| 587 @cindex arbitrary limits on data | |
| 588 Avoid arbitrary limits on the length or number of @emph{any} data | |
| 589 structure, including file names, lines, files, and symbols, by allocating | |
| 590 all data structures dynamically. In most Unix utilities, ``long lines | |
| 591 are silently truncated''. This is not acceptable in a GNU utility. | |
| 592 | |
| 593 @cindex @code{NUL} characters | |
| 14719 | 594 @findex libiconv |
| 4958 | 595 Utilities reading files should not drop NUL characters, or any other |
| 596 nonprinting characters @emph{including those with codes above 0177}. | |
| 597 The only sensible exceptions would be utilities specifically intended | |
| 16159 | 598 for interface to certain types of terminals or printers that can't |
| 599 handle those characters. Whenever possible, try to make programs work | |
| 600 properly with sequences of bytes that represent multibyte characters; | |
| 16158 | 601 UTF-8 is the most important. |
| 4958 | 602 |
| 603 @cindex error messages | |
| 14719 | 604 Check every system call for an error return, unless you know you wish |
| 605 to ignore errors. Include the system error text (from @code{perror}, | |
| 606 @code{strerror}, or equivalent) in @emph{every} error message | |
| 607 resulting from a failing system call, as well as the name of the file | |
| 608 if any and the name of the utility. Just ``cannot open foo.c'' or | |
| 609 ``stat failed'' is not sufficient. | |
| 4958 | 610 |
| 611 @cindex @code{malloc} return value | |
| 612 @cindex memory allocation failure | |
| 613 Check every call to @code{malloc} or @code{realloc} to see if it | |
| 614 returned zero. Check @code{realloc} even if you are making the block | |
| 615 smaller; in a system that rounds block sizes to a power of 2, | |
| 616 @code{realloc} may get a different block if you ask for less space. | |
| 617 | |
| 618 In Unix, @code{realloc} can destroy the storage block if it returns | |
| 619 zero. GNU @code{realloc} does not have this bug: if it fails, the | |
| 620 original block is unchanged. Feel free to assume the bug is fixed. If | |
| 621 you wish to run your program on Unix, and wish to avoid lossage in this | |
| 622 case, you can use the GNU @code{malloc}. | |
| 623 | |
| 624 You must expect @code{free} to alter the contents of the block that was | |
| 625 freed. Anything you want to fetch from the block, you must fetch before | |
| 626 calling @code{free}. | |
| 627 | |
| 628 If @code{malloc} fails in a noninteractive program, make that a fatal | |
| 629 error. In an interactive program (one that reads commands from the | |
| 630 user), it is better to abort the command and return to the command | |
| 631 reader loop. This allows the user to kill other processes to free up | |
| 632 virtual memory, and then try the command again. | |
| 633 | |
| 634 @cindex command-line arguments, decoding | |
| 635 Use @code{getopt_long} to decode arguments, unless the argument syntax | |
| 636 makes this unreasonable. | |
| 637 | |
| 638 When static storage is to be written in during program execution, use | |
| 639 explicit C code to initialize it. Reserve C initialized declarations | |
| 640 for data that will not be changed. | |
| 641 @c ADR: why? | |
| 642 | |
| 643 Try to avoid low-level interfaces to obscure Unix data structures (such | |
| 644 as file directories, utmp, or the layout of kernel memory), since these | |
| 645 are less likely to work compatibly. If you need to find all the files | |
| 646 in a directory, use @code{readdir} or some other high-level interface. | |
| 647 These are supported compatibly by GNU. | |
| 648 | |
| 649 @cindex signal handling | |
| 650 The preferred signal handling facilities are the BSD variant of | |
| 17256 | 651 @code{signal}, and the POSIX @code{sigaction} function; the |
| 4958 | 652 alternative USG @code{signal} interface is an inferior design. |
| 653 | |
| 17256 | 654 Nowadays, using the POSIX signal functions may be the easiest way |
| 4958 | 655 to make a program portable. If you use @code{signal}, then on GNU/Linux |
| 656 systems running GNU libc version 1, you should include | |
| 657 @file{bsd/signal.h} instead of @file{signal.h}, so as to get BSD | |
| 658 behavior. It is up to you whether to support systems where | |
| 659 @code{signal} has only the USG behavior, or give up on them. | |
| 660 | |
| 661 @cindex impossible conditions | |
| 662 In error checks that detect ``impossible'' conditions, just abort. | |
| 663 There is usually no point in printing any message. These checks | |
| 664 indicate the existence of bugs. Whoever wants to fix the bugs will have | |
| 665 to read the source code and run a debugger. So explain the problem with | |
| 666 comments in the source. The relevant data will be in variables, which | |
| 667 are easy to examine with the debugger, so there is no point moving them | |
| 668 elsewhere. | |
| 669 | |
| 670 Do not use a count of errors as the exit status for a program. | |
| 671 @emph{That does not work}, because exit status values are limited to 8 | |
| 672 bits (0 through 255). A single run of the program might have 256 | |
| 673 errors; if you try to return 256 as the exit status, the parent process | |
| 674 will see 0 as the status, and it will appear that the program succeeded. | |
| 675 | |
| 676 @cindex temporary files | |
| 677 @cindex @code{TMPDIR} environment variable | |
| 678 If you make temporary files, check the @code{TMPDIR} environment | |
| 679 variable; if that variable is defined, use the specified directory | |
| 680 instead of @file{/tmp}. | |
| 681 | |
| 682 In addition, be aware that there is a possible security problem when | |
| 683 creating temporary files in world-writable directories. In C, you can | |
| 684 avoid this problem by creating temporary files in this manner: | |
| 685 | |
| 686 @example | |
| 12897 | 687 fd = open (filename, O_WRONLY | O_CREAT | O_EXCL, 0600); |
| 4958 | 688 @end example |
| 689 | |
| 690 @noindent | |
| 14502 | 691 or by using the @code{mkstemps} function from Gnulib |
| 692 (@pxref{mkstemps,,, gnulib, Gnulib}). | |
| 4958 | 693 |
| 14242 | 694 In bash, use @code{set -C} (long name @code{noclobber}) to avoid this |
| 695 problem. In addition, the @code{mktemp} utility is a more general | |
| 696 solution for creating temporary files from shell scripts | |
| 697 (@pxref{mktemp invocation,,, coreutils, GNU Coreutils}). | |
| 698 | |
| 4958 | 699 |
| 700 @node Libraries | |
| 701 @section Library Behavior | |
| 702 @cindex libraries | |
| 703 | |
| 704 Try to make library functions reentrant. If they need to do dynamic | |
| 705 storage allocation, at least try to avoid any nonreentrancy aside from | |
| 706 that of @code{malloc} itself. | |
| 707 | |
| 708 Here are certain name conventions for libraries, to avoid name | |
| 709 conflicts. | |
| 710 | |
| 711 Choose a name prefix for the library, more than two characters long. | |
| 712 All external function and variable names should start with this | |
| 713 prefix. In addition, there should only be one of these in any given | |
| 714 library member. This usually means putting each one in a separate | |
| 715 source file. | |
| 716 | |
| 717 An exception can be made when two external symbols are always used | |
| 718 together, so that no reasonable program could use one without the | |
| 719 other; then they can both go in the same file. | |
| 720 | |
| 721 External symbols that are not documented entry points for the user | |
| 722 should have names beginning with @samp{_}. The @samp{_} should be | |
| 723 followed by the chosen name prefix for the library, to prevent | |
| 724 collisions with other libraries. These can go in the same files with | |
| 725 user entry points if you like. | |
| 726 | |
| 727 Static functions and variables can be used as you like and need not | |
| 728 fit any naming convention. | |
| 729 | |
| 730 @node Errors | |
| 731 @section Formatting Error Messages | |
| 732 @cindex formatting error messages | |
| 733 @cindex error messages, formatting | |
| 734 | |
| 735 Error messages from compilers should look like this: | |
| 736 | |
| 737 @example | |
| 16279 | 738 @var{sourcefile}:@var{lineno}: @var{message} |
| 4958 | 739 @end example |
| 740 | |
| 741 @noindent | |
| 742 If you want to mention the column number, use one of these formats: | |
| 743 | |
| 744 @example | |
| 16279 | 745 @var{sourcefile}:@var{lineno}:@var{column}: @var{message} |
| 746 @var{sourcefile}:@var{lineno}.@var{column}: @var{message} | |
| 4958 | 747 |
| 748 @end example | |
| 749 | |
| 750 @noindent | |
| 751 Line numbers should start from 1 at the beginning of the file, and | |
| 16159 | 752 column numbers should start from 1 at the beginning of the line. |
| 753 (Both of these conventions are chosen for compatibility.) Calculate | |
| 754 column numbers assuming that space and all ASCII printing characters | |
| 755 have equal width, and assuming tab stops every 8 columns. For | |
| 756 non-ASCII characters, Unicode character widths should be used when in | |
| 757 a UTF-8 locale; GNU libc and GNU gnulib provide suitable | |
| 758 @code{wcwidth} functions. | |
| 4958 | 759 |
| 760 The error message can also give both the starting and ending positions | |
| 761 of the erroneous text. There are several formats so that you can | |
| 762 avoid redundant information such as a duplicate line number. | |
| 763 Here are the possible formats: | |
| 764 | |
| 765 @example | |
| 16279 | 766 @var{sourcefile}:@var{line1}.@var{column1}-@var{line2}.@var{column2}: @var{message} |
| 767 @var{sourcefile}:@var{line1}.@var{column1}-@var{column2}: @var{message} | |
| 768 @var{sourcefile}:@var{line1}-@var{line2}: @var{message} | |
| 4958 | 769 @end example |
| 770 | |
| 771 @noindent | |
| 772 When an error is spread over several files, you can use this format: | |
| 773 | |
| 774 @example | |
| 16279 | 775 @var{file1}:@var{line1}.@var{column1}-@var{file2}:@var{line2}.@var{column2}: @var{message} |
| 4958 | 776 @end example |
| 777 | |
| 778 Error messages from other noninteractive programs should look like this: | |
| 779 | |
| 780 @example | |
| 16279 | 781 @var{program}:@var{sourcefile}:@var{lineno}: @var{message} |
| 4958 | 782 @end example |
| 783 | |
| 784 @noindent | |
| 785 when there is an appropriate source file, or like this: | |
| 786 | |
| 787 @example | |
| 788 @var{program}: @var{message} | |
| 789 @end example | |
| 790 | |
| 791 @noindent | |
| 792 when there is no relevant source file. | |
| 793 | |
| 794 If you want to mention the column number, use this format: | |
| 795 | |
| 796 @example | |
| 16279 | 797 @var{program}:@var{sourcefile}:@var{lineno}:@var{column}: @var{message} |
| 4958 | 798 @end example |
| 799 | |
| 800 In an interactive program (one that is reading commands from a | |
| 801 terminal), it is better not to include the program name in an error | |
| 802 message. The place to indicate which program is running is in the | |
| 803 prompt or with the screen layout. (When the same program runs with | |
| 804 input from a source other than a terminal, it is not interactive and | |
| 805 would do best to print error messages using the noninteractive style.) | |
| 806 | |
| 807 The string @var{message} should not begin with a capital letter when | |
| 808 it follows a program name and/or file name, because that isn't the | |
| 809 beginning of a sentence. (The sentence conceptually starts at the | |
| 810 beginning of the line.) Also, it should not end with a period. | |
| 811 | |
| 812 Error messages from interactive programs, and other messages such as | |
| 813 usage messages, should start with a capital letter. But they should not | |
| 814 end with a period. | |
| 815 | |
| 816 @node User Interfaces | |
| 817 @section Standards for Interfaces Generally | |
| 818 | |
| 819 @cindex program name and its behavior | |
| 820 @cindex behavior, dependent on program's name | |
| 821 Please don't make the behavior of a utility depend on the name used | |
| 822 to invoke it. It is useful sometimes to make a link to a utility | |
| 823 with a different name, and that should not change what it does. | |
| 824 | |
| 825 Instead, use a run time option or a compilation switch or both | |
| 826 to select among the alternate behaviors. | |
| 827 | |
| 828 @cindex output device and program's behavior | |
| 829 Likewise, please don't make the behavior of the program depend on the | |
| 830 type of output device it is used with. Device independence is an | |
| 831 important principle of the system's design; do not compromise it merely | |
| 832 to save someone from typing an option now and then. (Variation in error | |
| 833 message syntax when using a terminal is ok, because that is a side issue | |
| 834 that people do not depend on.) | |
| 835 | |
| 836 If you think one behavior is most useful when the output is to a | |
| 837 terminal, and another is most useful when the output is a file or a | |
| 838 pipe, then it is usually best to make the default behavior the one that | |
| 839 is useful with output to a terminal, and have an option for the other | |
| 840 behavior. | |
| 841 | |
| 842 Compatibility requires certain programs to depend on the type of output | |
| 843 device. It would be disastrous if @code{ls} or @code{sh} did not do so | |
| 844 in the way all users expect. In some of these cases, we supplement the | |
| 845 program with a preferred alternate version that does not depend on the | |
| 846 output device type. For example, we provide a @code{dir} program much | |
| 847 like @code{ls} except that its default output format is always | |
| 848 multi-column format. | |
| 849 | |
| 9019 | 850 |
| 4958 | 851 @node Graphical Interfaces |
| 852 @section Standards for Graphical Interfaces | |
| 853 @cindex graphical user interface | |
| 13072 | 854 @cindex interface styles |
| 855 @cindex user interface styles | |
| 856 | |
| 857 @cindex GTK+ | |
| 4958 | 858 When you write a program that provides a graphical user interface, |
| 13049 | 859 please make it work with the X Window System and the GTK+ toolkit |
| 860 unless the functionality specifically requires some alternative (for | |
| 861 example, ``displaying jpeg images while in console mode''). | |
| 4958 | 862 |
| 863 In addition, please provide a command-line interface to control the | |
| 864 functionality. (In many cases, the graphical user interface can be a | |
| 865 separate program which invokes the command-line program.) This is | |
| 866 so that the same jobs can be done from scripts. | |
| 867 | |
| 13072 | 868 @cindex CORBA |
| 869 @cindex GNOME | |
| 870 @cindex D-bus | |
| 871 @cindex keyboard interface | |
| 872 @cindex library interface | |
| 873 Please also consider providing a D-bus interface for use from other | |
| 874 running programs, such as within GNOME. (GNOME used to use CORBA | |
| 875 for this, but that is being phased out.) In addition, consider | |
| 876 providing a library interface (for use from C), and perhaps a | |
| 877 keyboard-driven console interface (for use by users from console | |
| 878 mode). Once you are doing the work to provide the functionality and | |
| 879 the graphical interface, these won't be much extra work. | |
| 4958 | 880 |
| 881 @node Command-Line Interfaces | |
| 882 @section Standards for Command Line Interfaces | |
| 883 @cindex command-line interface | |
| 884 | |
| 885 @findex getopt | |
| 17256 | 886 It is a good idea to follow the POSIX guidelines for the |
| 4958 | 887 command-line options of a program. The easiest way to do this is to use |
| 888 @code{getopt} to parse them. Note that the GNU version of @code{getopt} | |
| 889 will normally permit options anywhere among the arguments unless the | |
| 17256 | 890 special argument @samp{--} is used. This is not what POSIX |
| 4958 | 891 specifies; it is a GNU extension. |
| 892 | |
| 893 @cindex long-named options | |
| 894 Please define long-named options that are equivalent to the | |
| 895 single-letter Unix-style options. We hope to make GNU more user | |
| 896 friendly this way. This is easy to do with the GNU function | |
| 897 @code{getopt_long}. | |
| 898 | |
| 899 One of the advantages of long-named options is that they can be | |
| 900 consistent from program to program. For example, users should be able | |
| 901 to expect the ``verbose'' option of any GNU program which has one, to be | |
| 902 spelled precisely @samp{--verbose}. To achieve this uniformity, look at | |
| 903 the table of common long-option names when you choose the option names | |
| 904 for your program (@pxref{Option Table}). | |
| 905 | |
| 906 It is usually a good idea for file names given as ordinary arguments to | |
| 907 be input files only; any output files would be specified using options | |
| 908 (preferably @samp{-o} or @samp{--output}). Even if you allow an output | |
| 909 file name as an ordinary argument for compatibility, try to provide an | |
| 910 option as another way to specify it. This will lead to more consistency | |
| 6946 | 911 among GNU utilities, and fewer idiosyncrasies for users to remember. |
| 4958 | 912 |
| 913 @cindex standard command-line options | |
| 914 @cindex options, standard command-line | |
| 915 @cindex CGI programs, standard options for | |
| 916 @cindex PATH_INFO, specifying standard options as | |
| 917 All programs should support two standard options: @samp{--version} | |
| 918 and @samp{--help}. CGI programs should accept these as command-line | |
| 919 options, and also if given as the @env{PATH_INFO}; for instance, | |
| 920 visiting @url{http://example.org/p.cgi/--help} in a browser should | |
| 5909 | 921 output the same information as invoking @samp{p.cgi --help} from the |
| 4958 | 922 command line. |
| 923 | |
| 9019 | 924 @menu |
| 925 * --version:: The standard output for --version. | |
| 926 * --help:: The standard output for --help. | |
| 927 @end menu | |
| 928 | |
| 929 @node --version | |
| 930 @subsection @option{--version} | |
| 931 | |
| 932 @cindex @samp{--version} output | |
| 933 | |
| 934 The standard @code{--version} option should direct the program to | |
| 935 print information about its name, version, origin and legal status, | |
| 936 all on standard output, and then exit successfully. Other options and | |
| 937 arguments should be ignored once this is seen, and the program should | |
| 938 not perform its normal function. | |
| 4958 | 939 |
| 940 @cindex canonical name of a program | |
| 941 @cindex program's canonical name | |
| 942 The first line is meant to be easy for a program to parse; the version | |
| 943 number proper starts after the last space. In addition, it contains | |
| 944 the canonical name for this program, in this format: | |
| 945 | |
| 946 @example | |
| 947 GNU Emacs 19.30 | |
| 948 @end example | |
| 949 | |
| 950 @noindent | |
| 951 The program's name should be a constant string; @emph{don't} compute it | |
| 952 from @code{argv[0]}. The idea is to state the standard or canonical | |
| 953 name for the program, not its file name. There are other ways to find | |
| 954 out the precise file name where a command is found in @code{PATH}. | |
| 955 | |
| 956 If the program is a subsidiary part of a larger package, mention the | |
| 957 package name in parentheses, like this: | |
| 958 | |
| 959 @example | |
| 960 emacsserver (GNU Emacs) 19.30 | |
| 961 @end example | |
| 962 | |
| 963 @noindent | |
| 964 If the package has a version number which is different from this | |
| 965 program's version number, you can mention the package version number | |
| 966 just before the close-parenthesis. | |
| 967 | |
| 9019 | 968 If you @emph{need} to mention the version numbers of libraries which |
| 4958 | 969 are distributed separately from the package which contains this program, |
| 970 you can do so by printing an additional line of version info for each | |
| 971 library you want to mention. Use the same format for these lines as for | |
| 972 the first line. | |
| 973 | |
| 974 Please do not mention all of the libraries that the program uses ``just | |
| 975 for completeness''---that would produce a lot of unhelpful clutter. | |
| 976 Please mention library version numbers only if you find in practice that | |
| 977 they are very important to you in debugging. | |
| 978 | |
| 979 The following line, after the version number line or lines, should be a | |
| 980 copyright notice. If more than one copyright notice is called for, put | |
| 981 each on a separate line. | |
| 982 | |
| 9019 | 983 Next should follow a line stating the license, preferably using one of |
| 16359 | 984 abbreviations below, and a brief statement that the program is free |
| 9019 | 985 software, and that users are free to copy and change it. Also mention |
| 986 that there is no warranty, to the extent permitted by law. See | |
| 987 recommended wording below. | |
| 4958 | 988 |
| 989 It is ok to finish the output with a list of the major authors of the | |
| 990 program, as a way of giving credit. | |
| 991 | |
| 992 Here's an example of output that follows these rules: | |
| 993 | |
| 994 @smallexample | |
| 9019 | 995 GNU hello 2.3 |
| 996 Copyright (C) 2007 Free Software Foundation, Inc. | |
| 997 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> | |
| 998 This is free software: you are free to change and redistribute it. | |
| 999 There is NO WARRANTY, to the extent permitted by law. | |
| 4958 | 1000 @end smallexample |
| 1001 | |
| 1002 You should adapt this to your program, of course, filling in the proper | |
| 1003 year, copyright holder, name of program, and the references to | |
| 1004 distribution terms, and changing the rest of the wording as necessary. | |
| 1005 | |
| 1006 This copyright notice only needs to mention the most recent year in | |
| 1007 which changes were made---there's no need to list the years for previous | |
| 1008 versions' changes. You don't have to mention the name of the program in | |
| 1009 these notices, if that is inconvenient, since it appeared in the first | |
| 6640 | 1010 line. (The rules are different for copyright notices in source files; |
| 9019 | 1011 @pxref{Copyright Notices,,,maintain,Information for GNU Maintainers}.) |
| 4958 | 1012 |
| 1013 Translations of the above lines must preserve the validity of the | |
| 1014 copyright notices (@pxref{Internationalization}). If the translation's | |
| 1015 character set supports it, the @samp{(C)} should be replaced with the | |
| 1016 copyright symbol, as follows: | |
| 1017 | |
| 6725 | 1018 @ifinfo |
| 1019 (the official copyright symbol, which is the letter C in a circle); | |
| 1020 @end ifinfo | |
| 1021 @ifnotinfo | |
| 4958 | 1022 @copyright{} |
| 6725 | 1023 @end ifnotinfo |
| 4958 | 1024 |
| 1025 Write the word ``Copyright'' exactly like that, in English. Do not | |
| 1026 translate it into another language. International treaties recognize | |
| 1027 the English word ``Copyright''; translations into other languages do not | |
| 1028 have legal significance. | |
| 1029 | |
| 9019 | 1030 Finally, here is the table of our suggested license abbreviations. |
| 1031 Any abbreviation can be followed by @samp{v@var{version}[+]}, meaning | |
| 1032 that particular version, or later versions with the @samp{+}, as shown | |
| 17163 | 1033 above. In the case of a GNU license, @emph{always} indicate the permitted |
| 1034 versions in this way. | |
| 9019 | 1035 |
| 1036 In the case of exceptions for extra permissions with the GPL, we use | |
| 1037 @samp{/} for a separator; the version number can follow the license | |
| 1038 abbreviation as usual, as in the examples below. | |
| 1039 | |
| 1040 @table @asis | |
| 1041 @item GPL | |
| 9823 | 1042 GNU General Public License, @url{http://www.gnu.org/@/licenses/@/gpl.html}. |
| 9019 | 1043 |
| 1044 @item LGPL | |
| 9823 | 1045 GNU Lesser General Public License, @url{http://www.gnu.org/@/licenses/@/lgpl.html}. |
| 9019 | 1046 |
| 10037 | 1047 @item GPL/Ada |
| 9019 | 1048 GNU GPL with the exception for Ada. |
| 1049 | |
| 1050 @item Apache | |
| 1051 The Apache Software Foundation license, | |
| 9823 | 1052 @url{http://www.apache.org/@/licenses}. |
| 9019 | 1053 |
| 1054 @item Artistic | |
| 17382 | 1055 The Artistic license used for Perl, @url{http://dev.perl.org/licenses/artistic.html}. |
| 9019 | 1056 |
| 1057 @item Expat | |
| 9823 | 1058 The Expat license, @url{http://www.jclark.com/@/xml/@/copying.txt}. |
| 9019 | 1059 |
| 1060 @item MPL | |
| 9823 | 1061 The Mozilla Public License, @url{http://www.mozilla.org/@/MPL/}. |
| 9019 | 1062 |
| 1063 @item OBSD | |
| 1064 The original (4-clause) BSD license, incompatible with the GNU GPL | |
| 9823 | 1065 @url{http://www.xfree86.org/@/3.3.6/@/COPYRIGHT2.html#6}. |
| 9019 | 1066 |
| 1067 @item PHP | |
| 9823 | 1068 The license used for PHP, @url{http://www.php.net/@/license/}. |
| 9019 | 1069 |
| 1070 @item public domain | |
| 1071 The non-license that is being in the public domain, | |
| 9823 | 1072 @url{http://www.gnu.org/@/licenses/@/license-list.html#PublicDomain}. |
| 9019 | 1073 |
| 1074 @item Python | |
| 9823 | 1075 The license for Python, @url{http://www.python.org/@/2.0.1/@/license.html}. |
| 9019 | 1076 |
| 1077 @item RBSD | |
| 13219 | 1078 The revised (3-clause) BSD, compatible with the GNU GPL,@* |
| 9823 | 1079 @url{http://www.xfree86.org/@/3.3.6/@/COPYRIGHT2.html#5}. |
| 9019 | 1080 |
| 1081 @item X11 | |
| 1082 The simple non-copyleft license used for most versions of the X Window | |
| 13049 | 1083 System, @url{http://www.xfree86.org/@/3.3.6/@/COPYRIGHT2.html#3}. |
| 9019 | 1084 |
| 1085 @item Zlib | |
| 9823 | 1086 The license for Zlib, @url{http://www.gzip.org/@/zlib/@/zlib_license.html}. |
| 9019 | 1087 |
| 1088 @end table | |
| 1089 | |
| 1090 More information about these licenses and many more are on the GNU | |
| 1091 licensing web pages, | |
| 9823 | 1092 @url{http://www.gnu.org/@/licenses/@/license-list.html}. |
| 9019 | 1093 |
| 1094 | |
| 1095 @node --help | |
| 1096 @subsection @option{--help} | |
| 1097 | |
| 1098 @cindex @samp{--help} output | |
| 1099 | |
| 1100 The standard @code{--help} option should output brief documentation | |
| 1101 for how to invoke the program, on standard output, then exit | |
| 1102 successfully. Other options and arguments should be ignored once this | |
| 1103 is seen, and the program should not perform its normal function. | |
| 4958 | 1104 |
| 1105 @cindex address for bug reports | |
| 1106 @cindex bug reports | |
| 11097 | 1107 Near the end of the @samp{--help} option's output, please place lines |
| 1108 giving the email address for bug reports, the package's home page | |
| 1109 (normally @indicateurl{http://www.gnu.org/software/@var{pkg}}, and the | |
| 1110 general page for help using GNU programs. The format should be like this: | |
| 4958 | 1111 |
| 1112 @example | |
| 11116 | 1113 Report bugs to: @var{mailing-address} |
| 1114 @var{pkg} home page: <http://www.gnu.org/software/@var{pkg}/> | |
| 1115 General help using GNU software: <http://www.gnu.org/gethelp/> | |
| 4958 | 1116 @end example |
| 9019 | 1117 |
| 11097 | 1118 It is ok to mention other appropriate mailing lists and web pages. |
| 1119 | |
| 4958 | 1120 |
| 13575 | 1121 @node Dynamic Plug-In Interfaces |
| 1122 @section Standards for Dynamic Plug-in Interfaces | |
| 1123 @cindex plug-ins | |
| 1124 @cindex dynamic plug-ins | |
| 1125 | |
| 1126 Another aspect of keeping free programs free is encouraging | |
| 1127 development of free plug-ins, and discouraging development of | |
| 1128 proprietary plug-ins. Many GNU programs will not have anything like | |
| 1129 plug-ins at all, but those that do should follow these | |
| 1130 practices. | |
| 1131 | |
| 1132 First, the general plug-in architecture design should closely tie the | |
| 1133 plug-in to the original code, such that the plug-in and the base | |
| 1134 program are parts of one extended program. For GCC, for example, | |
| 1135 plug-ins receive and modify GCC's internal data structures, and so | |
| 1136 clearly form an extended program with the base GCC. | |
| 1137 | |
| 1138 @vindex plugin_is_GPL_compatible | |
| 1139 Second, you should require plug-in developers to affirm that their | |
| 1140 plug-ins are released under an appropriate license. This should be | |
| 1141 enforced with a simple programmatic check. For GCC, again for | |
| 1142 example, a plug-in must define the global symbol | |
| 1143 @code{plugin_is_GPL_compatible}, thus asserting that the plug-in is | |
| 1144 released under a GPL-compatible license (@pxref{Plugins,, Plugins, | |
| 1145 gccint, GCC Internals}). | |
| 1146 | |
| 1147 By adding this check to your program you are not creating a new legal | |
| 1148 requirement. The GPL itself requires plug-ins to be free software, | |
| 1149 licensed compatibly. As long as you have followed the first rule above | |
| 1150 to keep plug-ins closely tied to your original program, the GPL and AGPL | |
| 1151 already require those plug-ins to be released under a compatible | |
| 1152 license. The symbol definition in the plug-in---or whatever equivalent | |
| 1153 works best in your program---makes it harder for anyone who might | |
| 1154 distribute proprietary plug-ins to legally defend themselves. If a case | |
| 1155 about this got to court, we can point to that symbol as evidence that | |
| 1156 the plug-in developer understood that the license had this requirement. | |
| 1157 | |
| 1158 | |
| 4958 | 1159 @node Option Table |
| 1160 @section Table of Long Options | |
| 1161 @cindex long option names | |
| 1162 @cindex table of long options | |
| 1163 | |
| 1164 Here is a table of long options used by GNU programs. It is surely | |
| 1165 incomplete, but we aim to list all the options that a new program might | |
| 1166 want to be compatible with. If you use names not already in the table, | |
| 1167 please send @email{bug-standards@@gnu.org} a list of them, with their | |
| 1168 meanings, so we can update the table. | |
| 1169 | |
| 1170 @c Please leave newlines between items in this table; it's much easier | |
| 1171 @c to update when it isn't completely squashed together and unreadable. | |
| 1172 @c When there is more than one short option for a long option name, put | |
| 1173 @c a semicolon between the lists of the programs that use them, not a | |
| 1174 @c period. --friedman | |
| 1175 | |
| 1176 @table @samp | |
| 1177 @item after-date | |
| 1178 @samp{-N} in @code{tar}. | |
| 1179 | |
| 1180 @item all | |
| 1181 @samp{-a} in @code{du}, @code{ls}, @code{nm}, @code{stty}, @code{uname}, | |
| 1182 and @code{unexpand}. | |
| 1183 | |
| 1184 @item all-text | |
| 1185 @samp{-a} in @code{diff}. | |
| 1186 | |
| 1187 @item almost-all | |
| 1188 @samp{-A} in @code{ls}. | |
| 1189 | |
| 1190 @item append | |
| 1191 @samp{-a} in @code{etags}, @code{tee}, @code{time}; | |
| 1192 @samp{-r} in @code{tar}. | |
| 1193 | |
| 1194 @item archive | |
| 1195 @samp{-a} in @code{cp}. | |
| 1196 | |
| 1197 @item archive-name | |
| 1198 @samp{-n} in @code{shar}. | |
| 1199 | |
| 1200 @item arglength | |
| 1201 @samp{-l} in @code{m4}. | |
| 1202 | |
| 1203 @item ascii | |
| 1204 @samp{-a} in @code{diff}. | |
| 1205 | |
| 1206 @item assign | |
| 1207 @samp{-v} in @code{gawk}. | |
| 1208 | |
| 1209 @item assume-new | |
| 10199 | 1210 @samp{-W} in @code{make}. |
| 4958 | 1211 |
| 1212 @item assume-old | |
| 10199 | 1213 @samp{-o} in @code{make}. |
| 4958 | 1214 |
| 1215 @item auto-check | |
| 1216 @samp{-a} in @code{recode}. | |
| 1217 | |
| 1218 @item auto-pager | |
| 1219 @samp{-a} in @code{wdiff}. | |
| 1220 | |
| 1221 @item auto-reference | |
| 1222 @samp{-A} in @code{ptx}. | |
| 1223 | |
| 1224 @item avoid-wraps | |
| 1225 @samp{-n} in @code{wdiff}. | |
| 1226 | |
| 1227 @item background | |
| 1228 For server programs, run in the background. | |
| 1229 | |
| 1230 @item backward-search | |
| 1231 @samp{-B} in @code{ctags}. | |
| 1232 | |
| 1233 @item basename | |
| 1234 @samp{-f} in @code{shar}. | |
| 1235 | |
| 1236 @item batch | |
| 1237 Used in GDB. | |
| 1238 | |
| 1239 @item baud | |
| 1240 Used in GDB. | |
| 1241 | |
| 1242 @item before | |
| 1243 @samp{-b} in @code{tac}. | |
| 1244 | |
| 1245 @item binary | |
| 1246 @samp{-b} in @code{cpio} and @code{diff}. | |
| 1247 | |
| 1248 @item bits-per-code | |
| 1249 @samp{-b} in @code{shar}. | |
| 1250 | |
| 1251 @item block-size | |
| 1252 Used in @code{cpio} and @code{tar}. | |
| 1253 | |
| 1254 @item blocks | |
| 1255 @samp{-b} in @code{head} and @code{tail}. | |
| 1256 | |
| 1257 @item break-file | |
| 1258 @samp{-b} in @code{ptx}. | |
| 1259 | |
| 1260 @item brief | |
| 1261 Used in various programs to make output shorter. | |
| 1262 | |
| 1263 @item bytes | |
| 1264 @samp{-c} in @code{head}, @code{split}, and @code{tail}. | |
| 1265 | |
| 1266 @item c@t{++} | |
| 1267 @samp{-C} in @code{etags}. | |
| 1268 | |
| 1269 @item catenate | |
| 1270 @samp{-A} in @code{tar}. | |
| 1271 | |
| 1272 @item cd | |
| 1273 Used in various programs to specify the directory to use. | |
| 1274 | |
| 1275 @item changes | |
| 1276 @samp{-c} in @code{chgrp} and @code{chown}. | |
| 1277 | |
| 1278 @item classify | |
| 1279 @samp{-F} in @code{ls}. | |
| 1280 | |
| 1281 @item colons | |
| 1282 @samp{-c} in @code{recode}. | |
| 1283 | |
| 1284 @item command | |
| 1285 @samp{-c} in @code{su}; | |
| 1286 @samp{-x} in GDB. | |
| 1287 | |
| 1288 @item compare | |
| 1289 @samp{-d} in @code{tar}. | |
| 1290 | |
| 1291 @item compat | |
| 1292 Used in @code{gawk}. | |
| 1293 | |
| 1294 @item compress | |
| 1295 @samp{-Z} in @code{tar} and @code{shar}. | |
| 1296 | |
| 1297 @item concatenate | |
| 1298 @samp{-A} in @code{tar}. | |
| 1299 | |
| 1300 @item confirmation | |
| 1301 @samp{-w} in @code{tar}. | |
| 1302 | |
| 1303 @item context | |
| 1304 Used in @code{diff}. | |
| 1305 | |
| 1306 @item copyleft | |
| 1307 @samp{-W copyleft} in @code{gawk}. | |
| 1308 | |
| 1309 @item copyright | |
| 1310 @samp{-C} in @code{ptx}, @code{recode}, and @code{wdiff}; | |
| 1311 @samp{-W copyright} in @code{gawk}. | |
| 1312 | |
| 1313 @item core | |
| 1314 Used in GDB. | |
| 1315 | |
| 1316 @item count | |
| 1317 @samp{-q} in @code{who}. | |
| 1318 | |
| 1319 @item count-links | |
| 1320 @samp{-l} in @code{du}. | |
| 1321 | |
| 1322 @item create | |
| 1323 Used in @code{tar} and @code{cpio}. | |
| 1324 | |
| 1325 @item cut-mark | |
| 1326 @samp{-c} in @code{shar}. | |
| 1327 | |
| 1328 @item cxref | |
| 1329 @samp{-x} in @code{ctags}. | |
| 1330 | |
| 1331 @item date | |
| 1332 @samp{-d} in @code{touch}. | |
| 1333 | |
| 1334 @item debug | |
| 10199 | 1335 @samp{-d} in @code{make} and @code{m4}; |
| 4958 | 1336 @samp{-t} in Bison. |
| 1337 | |
| 1338 @item define | |
| 1339 @samp{-D} in @code{m4}. | |
| 1340 | |
| 1341 @item defines | |
| 1342 @samp{-d} in Bison and @code{ctags}. | |
| 1343 | |
| 1344 @item delete | |
| 1345 @samp{-D} in @code{tar}. | |
| 1346 | |
| 1347 @item dereference | |
| 1348 @samp{-L} in @code{chgrp}, @code{chown}, @code{cpio}, @code{du}, | |
| 1349 @code{ls}, and @code{tar}. | |
| 1350 | |
| 1351 @item dereference-args | |
| 1352 @samp{-D} in @code{du}. | |
| 1353 | |
| 1354 @item device | |
| 1355 Specify an I/O device (special file name). | |
| 1356 | |
| 1357 @item diacritics | |
| 1358 @samp{-d} in @code{recode}. | |
| 1359 | |
| 1360 @item dictionary-order | |
| 1361 @samp{-d} in @code{look}. | |
| 1362 | |
| 1363 @item diff | |
| 1364 @samp{-d} in @code{tar}. | |
| 1365 | |
| 1366 @item digits | |
| 1367 @samp{-n} in @code{csplit}. | |
| 1368 | |
| 1369 @item directory | |
| 1370 Specify the directory to use, in various programs. In @code{ls}, it | |
| 1371 means to show directories themselves rather than their contents. In | |
| 1372 @code{rm} and @code{ln}, it means to not treat links to directories | |
| 1373 specially. | |
| 1374 | |
| 1375 @item discard-all | |
| 1376 @samp{-x} in @code{strip}. | |
| 1377 | |
| 1378 @item discard-locals | |
| 1379 @samp{-X} in @code{strip}. | |
| 1380 | |
| 1381 @item dry-run | |
| 10199 | 1382 @samp{-n} in @code{make}. |
| 4958 | 1383 |
| 1384 @item ed | |
| 1385 @samp{-e} in @code{diff}. | |
| 1386 | |
| 1387 @item elide-empty-files | |
| 1388 @samp{-z} in @code{csplit}. | |
| 1389 | |
| 1390 @item end-delete | |
| 1391 @samp{-x} in @code{wdiff}. | |
| 1392 | |
| 1393 @item end-insert | |
| 1394 @samp{-z} in @code{wdiff}. | |
| 1395 | |
| 1396 @item entire-new-file | |
| 1397 @samp{-N} in @code{diff}. | |
| 1398 | |
| 1399 @item environment-overrides | |
| 10199 | 1400 @samp{-e} in @code{make}. |
| 4958 | 1401 |
| 1402 @item eof | |
| 1403 @samp{-e} in @code{xargs}. | |
| 1404 | |
| 1405 @item epoch | |
| 1406 Used in GDB. | |
| 1407 | |
| 1408 @item error-limit | |
| 1409 Used in @code{makeinfo}. | |
| 1410 | |
| 1411 @item error-output | |
| 1412 @samp{-o} in @code{m4}. | |
| 1413 | |
| 1414 @item escape | |
| 1415 @samp{-b} in @code{ls}. | |
| 1416 | |
| 1417 @item exclude-from | |
| 1418 @samp{-X} in @code{tar}. | |
| 1419 | |
| 1420 @item exec | |
| 1421 Used in GDB. | |
| 1422 | |
| 1423 @item exit | |
| 1424 @samp{-x} in @code{xargs}. | |
| 1425 | |
| 1426 @item exit-0 | |
| 1427 @samp{-e} in @code{unshar}. | |
| 1428 | |
| 1429 @item expand-tabs | |
| 1430 @samp{-t} in @code{diff}. | |
| 1431 | |
| 1432 @item expression | |
| 1433 @samp{-e} in @code{sed}. | |
| 1434 | |
| 1435 @item extern-only | |
| 1436 @samp{-g} in @code{nm}. | |
| 1437 | |
| 1438 @item extract | |
| 1439 @samp{-i} in @code{cpio}; | |
| 1440 @samp{-x} in @code{tar}. | |
| 1441 | |
| 1442 @item faces | |
| 1443 @samp{-f} in @code{finger}. | |
| 1444 | |
| 1445 @item fast | |
| 1446 @samp{-f} in @code{su}. | |
| 1447 | |
| 1448 @item fatal-warnings | |
| 1449 @samp{-E} in @code{m4}. | |
| 1450 | |
| 1451 @item file | |
| 10199 | 1452 @samp{-f} in @code{gawk}, @code{info}, @code{make}, @code{mt}, |
| 1453 @code{sed}, and @code{tar}. | |
| 4958 | 1454 |
| 1455 @item field-separator | |
| 1456 @samp{-F} in @code{gawk}. | |
| 1457 | |
| 1458 @item file-prefix | |
| 1459 @samp{-b} in Bison. | |
| 1460 | |
| 1461 @item file-type | |
| 1462 @samp{-F} in @code{ls}. | |
| 1463 | |
| 1464 @item files-from | |
| 1465 @samp{-T} in @code{tar}. | |
| 1466 | |
| 1467 @item fill-column | |
| 1468 Used in @code{makeinfo}. | |
| 1469 | |
| 1470 @item flag-truncation | |
| 1471 @samp{-F} in @code{ptx}. | |
| 1472 | |
| 1473 @item fixed-output-files | |
| 1474 @samp{-y} in Bison. | |
| 1475 | |
| 1476 @item follow | |
| 1477 @samp{-f} in @code{tail}. | |
| 1478 | |
| 1479 @item footnote-style | |
| 1480 Used in @code{makeinfo}. | |
| 1481 | |
| 1482 @item force | |
| 1483 @samp{-f} in @code{cp}, @code{ln}, @code{mv}, and @code{rm}. | |
| 1484 | |
| 1485 @item force-prefix | |
| 1486 @samp{-F} in @code{shar}. | |
| 1487 | |
| 1488 @item foreground | |
| 1489 For server programs, run in the foreground; | |
| 1490 in other words, don't do anything special to run the server | |
| 1491 in the background. | |
| 1492 | |
| 1493 @item format | |
| 1494 Used in @code{ls}, @code{time}, and @code{ptx}. | |
| 1495 | |
| 1496 @item freeze-state | |
| 1497 @samp{-F} in @code{m4}. | |
| 1498 | |
| 1499 @item fullname | |
| 1500 Used in GDB. | |
| 1501 | |
| 1502 @item gap-size | |
| 1503 @samp{-g} in @code{ptx}. | |
| 1504 | |
| 1505 @item get | |
| 1506 @samp{-x} in @code{tar}. | |
| 1507 | |
| 1508 @item graphic | |
| 1509 @samp{-i} in @code{ul}. | |
| 1510 | |
| 1511 @item graphics | |
| 1512 @samp{-g} in @code{recode}. | |
| 1513 | |
| 1514 @item group | |
| 1515 @samp{-g} in @code{install}. | |
| 1516 | |
| 1517 @item gzip | |
| 1518 @samp{-z} in @code{tar} and @code{shar}. | |
| 1519 | |
| 1520 @item hashsize | |
| 1521 @samp{-H} in @code{m4}. | |
| 1522 | |
| 1523 @item header | |
| 1524 @samp{-h} in @code{objdump} and @code{recode} | |
| 1525 | |
| 1526 @item heading | |
| 1527 @samp{-H} in @code{who}. | |
| 1528 | |
| 1529 @item help | |
| 1530 Used to ask for brief usage information. | |
| 1531 | |
| 1532 @item here-delimiter | |
| 1533 @samp{-d} in @code{shar}. | |
| 1534 | |
| 1535 @item hide-control-chars | |
| 1536 @samp{-q} in @code{ls}. | |
| 1537 | |
| 1538 @item html | |
| 1539 In @code{makeinfo}, output HTML. | |
| 1540 | |
| 1541 @item idle | |
| 1542 @samp{-u} in @code{who}. | |
| 1543 | |
| 1544 @item ifdef | |
| 1545 @samp{-D} in @code{diff}. | |
| 1546 | |
| 1547 @item ignore | |
| 1548 @samp{-I} in @code{ls}; | |
| 1549 @samp{-x} in @code{recode}. | |
| 1550 | |
| 1551 @item ignore-all-space | |
| 1552 @samp{-w} in @code{diff}. | |
| 1553 | |
| 1554 @item ignore-backups | |
| 1555 @samp{-B} in @code{ls}. | |
| 1556 | |
| 1557 @item ignore-blank-lines | |
| 1558 @samp{-B} in @code{diff}. | |
| 1559 | |
| 1560 @item ignore-case | |
| 1561 @samp{-f} in @code{look} and @code{ptx}; | |
| 1562 @samp{-i} in @code{diff} and @code{wdiff}. | |
| 1563 | |
| 1564 @item ignore-errors | |
| 10199 | 1565 @samp{-i} in @code{make}. |
| 4958 | 1566 |
| 1567 @item ignore-file | |
| 1568 @samp{-i} in @code{ptx}. | |
| 1569 | |
| 1570 @item ignore-indentation | |
| 1571 @samp{-I} in @code{etags}. | |
| 1572 | |
| 1573 @item ignore-init-file | |
| 1574 @samp{-f} in Oleo. | |
| 1575 | |
| 1576 @item ignore-interrupts | |
| 1577 @samp{-i} in @code{tee}. | |
| 1578 | |
| 1579 @item ignore-matching-lines | |
| 1580 @samp{-I} in @code{diff}. | |
| 1581 | |
| 1582 @item ignore-space-change | |
| 1583 @samp{-b} in @code{diff}. | |
| 1584 | |
| 1585 @item ignore-zeros | |
| 1586 @samp{-i} in @code{tar}. | |
| 1587 | |
| 1588 @item include | |
| 1589 @samp{-i} in @code{etags}; | |
| 1590 @samp{-I} in @code{m4}. | |
| 1591 | |
| 1592 @item include-dir | |
| 10199 | 1593 @samp{-I} in @code{make}. |
| 4958 | 1594 |
| 1595 @item incremental | |
| 1596 @samp{-G} in @code{tar}. | |
| 1597 | |
| 1598 @item info | |
| 1599 @samp{-i}, @samp{-l}, and @samp{-m} in Finger. | |
| 1600 | |
| 1601 @item init-file | |
| 1602 In some programs, specify the name of the file to read as the user's | |
| 1603 init file. | |
| 1604 | |
| 1605 @item initial | |
| 1606 @samp{-i} in @code{expand}. | |
| 1607 | |
| 1608 @item initial-tab | |
| 1609 @samp{-T} in @code{diff}. | |
| 1610 | |
| 1611 @item inode | |
| 1612 @samp{-i} in @code{ls}. | |
| 1613 | |
| 1614 @item interactive | |
| 1615 @samp{-i} in @code{cp}, @code{ln}, @code{mv}, @code{rm}; | |
| 1616 @samp{-e} in @code{m4}; | |
| 1617 @samp{-p} in @code{xargs}; | |
| 1618 @samp{-w} in @code{tar}. | |
| 1619 | |
| 1620 @item intermix-type | |
| 1621 @samp{-p} in @code{shar}. | |
| 1622 | |
| 1623 @item iso-8601 | |
| 1624 Used in @code{date} | |
| 1625 | |
| 1626 @item jobs | |
| 10199 | 1627 @samp{-j} in @code{make}. |
| 4958 | 1628 |
| 1629 @item just-print | |
| 10199 | 1630 @samp{-n} in @code{make}. |
| 4958 | 1631 |
| 1632 @item keep-going | |
| 10199 | 1633 @samp{-k} in @code{make}. |
| 4958 | 1634 |
| 1635 @item keep-files | |
| 1636 @samp{-k} in @code{csplit}. | |
| 1637 | |
| 1638 @item kilobytes | |
| 1639 @samp{-k} in @code{du} and @code{ls}. | |
| 1640 | |
| 1641 @item language | |
| 1642 @samp{-l} in @code{etags}. | |
| 1643 | |
| 1644 @item less-mode | |
| 1645 @samp{-l} in @code{wdiff}. | |
| 1646 | |
| 1647 @item level-for-gzip | |
| 1648 @samp{-g} in @code{shar}. | |
| 1649 | |
| 1650 @item line-bytes | |
| 1651 @samp{-C} in @code{split}. | |
| 1652 | |
| 1653 @item lines | |
| 1654 Used in @code{split}, @code{head}, and @code{tail}. | |
| 1655 | |
| 1656 @item link | |
| 1657 @samp{-l} in @code{cpio}. | |
| 1658 | |
| 1659 @item lint | |
| 1660 @itemx lint-old | |
| 1661 Used in @code{gawk}. | |
| 1662 | |
| 1663 @item list | |
| 1664 @samp{-t} in @code{cpio}; | |
| 1665 @samp{-l} in @code{recode}. | |
| 1666 | |
| 1667 @item list | |
| 1668 @samp{-t} in @code{tar}. | |
| 1669 | |
| 1670 @item literal | |
| 1671 @samp{-N} in @code{ls}. | |
| 1672 | |
| 1673 @item load-average | |
| 10199 | 1674 @samp{-l} in @code{make}. |
| 4958 | 1675 |
| 1676 @item login | |
| 1677 Used in @code{su}. | |
| 1678 | |
| 1679 @item machine | |
| 5560 | 1680 Used in @code{uname}. |
| 4958 | 1681 |
| 1682 @item macro-name | |
| 1683 @samp{-M} in @code{ptx}. | |
| 1684 | |
| 1685 @item mail | |
| 1686 @samp{-m} in @code{hello} and @code{uname}. | |
| 1687 | |
| 1688 @item make-directories | |
| 1689 @samp{-d} in @code{cpio}. | |
| 1690 | |
| 1691 @item makefile | |
| 10199 | 1692 @samp{-f} in @code{make}. |
| 4958 | 1693 |
| 1694 @item mapped | |
| 1695 Used in GDB. | |
| 1696 | |
| 1697 @item max-args | |
| 1698 @samp{-n} in @code{xargs}. | |
| 1699 | |
| 1700 @item max-chars | |
| 1701 @samp{-n} in @code{xargs}. | |
| 1702 | |
| 1703 @item max-lines | |
| 1704 @samp{-l} in @code{xargs}. | |
| 1705 | |
| 1706 @item max-load | |
| 10199 | 1707 @samp{-l} in @code{make}. |
| 4958 | 1708 |
| 1709 @item max-procs | |
| 1710 @samp{-P} in @code{xargs}. | |
| 1711 | |
| 1712 @item mesg | |
| 1713 @samp{-T} in @code{who}. | |
| 1714 | |
| 1715 @item message | |
| 1716 @samp{-T} in @code{who}. | |
| 1717 | |
| 1718 @item minimal | |
| 1719 @samp{-d} in @code{diff}. | |
| 1720 | |
| 1721 @item mixed-uuencode | |
| 1722 @samp{-M} in @code{shar}. | |
| 1723 | |
| 1724 @item mode | |
| 1725 @samp{-m} in @code{install}, @code{mkdir}, and @code{mkfifo}. | |
| 1726 | |
| 1727 @item modification-time | |
| 1728 @samp{-m} in @code{tar}. | |
| 1729 | |
| 1730 @item multi-volume | |
| 1731 @samp{-M} in @code{tar}. | |
| 1732 | |
| 1733 @item name-prefix | |
| 1734 @samp{-a} in Bison. | |
| 1735 | |
| 1736 @item nesting-limit | |
| 1737 @samp{-L} in @code{m4}. | |
| 1738 | |
| 1739 @item net-headers | |
| 1740 @samp{-a} in @code{shar}. | |
| 1741 | |
| 1742 @item new-file | |
| 10199 | 1743 @samp{-W} in @code{make}. |
| 4958 | 1744 |
| 1745 @item no-builtin-rules | |
| 10199 | 1746 @samp{-r} in @code{make}. |
| 4958 | 1747 |
| 1748 @item no-character-count | |
| 1749 @samp{-w} in @code{shar}. | |
| 1750 | |
| 1751 @item no-check-existing | |
| 1752 @samp{-x} in @code{shar}. | |
| 1753 | |
| 1754 @item no-common | |
| 1755 @samp{-3} in @code{wdiff}. | |
| 1756 | |
| 1757 @item no-create | |
| 1758 @samp{-c} in @code{touch}. | |
| 1759 | |
| 1760 @item no-defines | |
| 1761 @samp{-D} in @code{etags}. | |
| 1762 | |
| 1763 @item no-deleted | |
| 1764 @samp{-1} in @code{wdiff}. | |
| 1765 | |
| 1766 @item no-dereference | |
| 1767 @samp{-d} in @code{cp}. | |
| 1768 | |
| 1769 @item no-inserted | |
| 1770 @samp{-2} in @code{wdiff}. | |
| 1771 | |
| 1772 @item no-keep-going | |
| 10199 | 1773 @samp{-S} in @code{make}. |
| 4958 | 1774 |
| 1775 @item no-lines | |
| 1776 @samp{-l} in Bison. | |
| 1777 | |
| 1778 @item no-piping | |
| 1779 @samp{-P} in @code{shar}. | |
| 1780 | |
| 1781 @item no-prof | |
| 1782 @samp{-e} in @code{gprof}. | |
| 1783 | |
| 1784 @item no-regex | |
| 1785 @samp{-R} in @code{etags}. | |
| 1786 | |
| 1787 @item no-sort | |
| 1788 @samp{-p} in @code{nm}. | |
| 1789 | |
| 1790 @item no-splash | |
| 1791 Don't print a startup splash screen. | |
| 1792 | |
| 1793 @item no-split | |
| 1794 Used in @code{makeinfo}. | |
| 1795 | |
| 1796 @item no-static | |
| 1797 @samp{-a} in @code{gprof}. | |
| 1798 | |
| 1799 @item no-time | |
| 1800 @samp{-E} in @code{gprof}. | |
| 1801 | |
| 1802 @item no-timestamp | |
| 1803 @samp{-m} in @code{shar}. | |
| 1804 | |
| 1805 @item no-validate | |
| 1806 Used in @code{makeinfo}. | |
| 1807 | |
| 1808 @item no-wait | |
| 1809 Used in @code{emacsclient}. | |
| 1810 | |
| 1811 @item no-warn | |
| 1812 Used in various programs to inhibit warnings. | |
| 1813 | |
| 1814 @item node | |
| 1815 @samp{-n} in @code{info}. | |
| 1816 | |
| 1817 @item nodename | |
| 1818 @samp{-n} in @code{uname}. | |
| 1819 | |
| 1820 @item nonmatching | |
| 1821 @samp{-f} in @code{cpio}. | |
| 1822 | |
| 1823 @item nstuff | |
| 1824 @samp{-n} in @code{objdump}. | |
| 1825 | |
| 1826 @item null | |
| 1827 @samp{-0} in @code{xargs}. | |
| 1828 | |
| 1829 @item number | |
| 1830 @samp{-n} in @code{cat}. | |
| 1831 | |
| 1832 @item number-nonblank | |
| 1833 @samp{-b} in @code{cat}. | |
| 1834 | |
| 1835 @item numeric-sort | |
| 1836 @samp{-n} in @code{nm}. | |
| 1837 | |
| 1838 @item numeric-uid-gid | |
| 1839 @samp{-n} in @code{cpio} and @code{ls}. | |
| 1840 | |
| 1841 @item nx | |
| 1842 Used in GDB. | |
| 1843 | |
| 1844 @item old-archive | |
| 1845 @samp{-o} in @code{tar}. | |
| 1846 | |
| 1847 @item old-file | |
| 10199 | 1848 @samp{-o} in @code{make}. |
| 4958 | 1849 |
| 1850 @item one-file-system | |
| 1851 @samp{-l} in @code{tar}, @code{cp}, and @code{du}. | |
| 1852 | |
| 1853 @item only-file | |
| 1854 @samp{-o} in @code{ptx}. | |
| 1855 | |
| 1856 @item only-prof | |
| 1857 @samp{-f} in @code{gprof}. | |
| 1858 | |
| 1859 @item only-time | |
| 1860 @samp{-F} in @code{gprof}. | |
| 1861 | |
| 1862 @item options | |
| 1863 @samp{-o} in @code{getopt}, @code{fdlist}, @code{fdmount}, | |
| 1864 @code{fdmountd}, and @code{fdumount}. | |
| 1865 | |
| 1866 @item output | |
| 1867 In various programs, specify the output file name. | |
| 1868 | |
| 1869 @item output-prefix | |
| 1870 @samp{-o} in @code{shar}. | |
| 1871 | |
| 1872 @item override | |
| 1873 @samp{-o} in @code{rm}. | |
| 1874 | |
| 1875 @item overwrite | |
| 1876 @samp{-c} in @code{unshar}. | |
| 1877 | |
| 1878 @item owner | |
| 1879 @samp{-o} in @code{install}. | |
| 1880 | |
| 1881 @item paginate | |
| 1882 @samp{-l} in @code{diff}. | |
| 1883 | |
| 1884 @item paragraph-indent | |
| 1885 Used in @code{makeinfo}. | |
| 1886 | |
| 1887 @item parents | |
| 1888 @samp{-p} in @code{mkdir} and @code{rmdir}. | |
| 1889 | |
| 1890 @item pass-all | |
| 1891 @samp{-p} in @code{ul}. | |
| 1892 | |
| 1893 @item pass-through | |
| 1894 @samp{-p} in @code{cpio}. | |
| 1895 | |
| 1896 @item port | |
| 1897 @samp{-P} in @code{finger}. | |
| 1898 | |
| 1899 @item portability | |
| 1900 @samp{-c} in @code{cpio} and @code{tar}. | |
| 1901 | |
| 1902 @item posix | |
| 1903 Used in @code{gawk}. | |
| 1904 | |
| 1905 @item prefix-builtins | |
| 1906 @samp{-P} in @code{m4}. | |
| 1907 | |
| 1908 @item prefix | |
| 1909 @samp{-f} in @code{csplit}. | |
| 1910 | |
| 1911 @item preserve | |
| 1912 Used in @code{tar} and @code{cp}. | |
| 1913 | |
| 1914 @item preserve-environment | |
| 1915 @samp{-p} in @code{su}. | |
| 1916 | |
| 1917 @item preserve-modification-time | |
| 1918 @samp{-m} in @code{cpio}. | |
| 1919 | |
| 1920 @item preserve-order | |
| 1921 @samp{-s} in @code{tar}. | |
| 1922 | |
| 1923 @item preserve-permissions | |
| 1924 @samp{-p} in @code{tar}. | |
| 1925 | |
| 1926 @item print | |
| 1927 @samp{-l} in @code{diff}. | |
| 1928 | |
| 1929 @item print-chars | |
| 1930 @samp{-L} in @code{cmp}. | |
| 1931 | |
| 1932 @item print-data-base | |
| 10199 | 1933 @samp{-p} in @code{make}. |
| 4958 | 1934 |
| 1935 @item print-directory | |
| 10199 | 1936 @samp{-w} in @code{make}. |
| 4958 | 1937 |
| 1938 @item print-file-name | |
| 1939 @samp{-o} in @code{nm}. | |
| 1940 | |
| 1941 @item print-symdefs | |
| 1942 @samp{-s} in @code{nm}. | |
| 1943 | |
| 1944 @item printer | |
| 1945 @samp{-p} in @code{wdiff}. | |
| 1946 | |
| 1947 @item prompt | |
| 1948 @samp{-p} in @code{ed}. | |
| 1949 | |
| 1950 @item proxy | |
| 1951 Specify an HTTP proxy. | |
| 1952 | |
| 1953 @item query-user | |
| 1954 @samp{-X} in @code{shar}. | |
| 1955 | |
| 1956 @item question | |
| 10199 | 1957 @samp{-q} in @code{make}. |
| 4958 | 1958 |
| 1959 @item quiet | |
| 1960 Used in many programs to inhibit the usual output. Every | |
| 1961 program accepting @samp{--quiet} should accept @samp{--silent} as a | |
| 1962 synonym. | |
| 1963 | |
| 1964 @item quiet-unshar | |
| 1965 @samp{-Q} in @code{shar} | |
| 1966 | |
| 1967 @item quote-name | |
| 1968 @samp{-Q} in @code{ls}. | |
| 1969 | |
| 1970 @item rcs | |
| 1971 @samp{-n} in @code{diff}. | |
| 1972 | |
| 1973 @item re-interval | |
| 1974 Used in @code{gawk}. | |
| 1975 | |
| 1976 @item read-full-blocks | |
| 1977 @samp{-B} in @code{tar}. | |
| 1978 | |
| 1979 @item readnow | |
| 1980 Used in GDB. | |
| 1981 | |
| 1982 @item recon | |
| 10199 | 1983 @samp{-n} in @code{make}. |
| 4958 | 1984 |
| 1985 @item record-number | |
| 1986 @samp{-R} in @code{tar}. | |
| 1987 | |
| 1988 @item recursive | |
| 1989 Used in @code{chgrp}, @code{chown}, @code{cp}, @code{ls}, @code{diff}, | |
| 1990 and @code{rm}. | |
| 1991 | |
| 10199 | 1992 @item reference |
| 1993 @samp{-r} in @code{touch}. | |
| 4958 | 1994 |
| 1995 @item references | |
| 1996 @samp{-r} in @code{ptx}. | |
| 1997 | |
| 1998 @item regex | |
| 1999 @samp{-r} in @code{tac} and @code{etags}. | |
| 2000 | |
| 2001 @item release | |
| 2002 @samp{-r} in @code{uname}. | |
| 2003 | |
| 2004 @item reload-state | |
| 2005 @samp{-R} in @code{m4}. | |
| 2006 | |
| 2007 @item relocation | |
| 2008 @samp{-r} in @code{objdump}. | |
| 2009 | |
| 2010 @item rename | |
| 2011 @samp{-r} in @code{cpio}. | |
| 2012 | |
| 2013 @item replace | |
| 2014 @samp{-i} in @code{xargs}. | |
| 2015 | |
| 2016 @item report-identical-files | |
| 2017 @samp{-s} in @code{diff}. | |
| 2018 | |
| 2019 @item reset-access-time | |
| 2020 @samp{-a} in @code{cpio}. | |
| 2021 | |
| 2022 @item reverse | |
| 2023 @samp{-r} in @code{ls} and @code{nm}. | |
| 2024 | |
| 2025 @item reversed-ed | |
| 2026 @samp{-f} in @code{diff}. | |
| 2027 | |
| 2028 @item right-side-defs | |
| 2029 @samp{-R} in @code{ptx}. | |
| 2030 | |
| 2031 @item same-order | |
| 2032 @samp{-s} in @code{tar}. | |
| 2033 | |
| 2034 @item same-permissions | |
| 2035 @samp{-p} in @code{tar}. | |
| 2036 | |
| 2037 @item save | |
| 2038 @samp{-g} in @code{stty}. | |
| 2039 | |
| 2040 @item se | |
| 2041 Used in GDB. | |
| 2042 | |
| 2043 @item sentence-regexp | |
| 2044 @samp{-S} in @code{ptx}. | |
| 2045 | |
| 2046 @item separate-dirs | |
| 2047 @samp{-S} in @code{du}. | |
| 2048 | |
| 2049 @item separator | |
| 2050 @samp{-s} in @code{tac}. | |
| 2051 | |
| 2052 @item sequence | |
| 2053 Used by @code{recode} to chose files or pipes for sequencing passes. | |
| 2054 | |
| 2055 @item shell | |
| 2056 @samp{-s} in @code{su}. | |
| 2057 | |
| 2058 @item show-all | |
| 2059 @samp{-A} in @code{cat}. | |
| 2060 | |
| 2061 @item show-c-function | |
| 2062 @samp{-p} in @code{diff}. | |
| 2063 | |
| 2064 @item show-ends | |
| 2065 @samp{-E} in @code{cat}. | |
| 2066 | |
| 2067 @item show-function-line | |
| 2068 @samp{-F} in @code{diff}. | |
| 2069 | |
| 2070 @item show-tabs | |
| 2071 @samp{-T} in @code{cat}. | |
| 2072 | |
| 2073 @item silent | |
| 2074 Used in many programs to inhibit the usual output. | |
| 2075 Every program accepting | |
| 2076 @samp{--silent} should accept @samp{--quiet} as a synonym. | |
| 2077 | |
| 2078 @item size | |
| 2079 @samp{-s} in @code{ls}. | |
| 2080 | |
| 2081 @item socket | |
| 2082 Specify a file descriptor for a network server to use for its socket, | |
| 2083 instead of opening and binding a new socket. This provides a way to | |
| 6946 | 2084 run, in a non-privileged process, a server that normally needs a |
| 4958 | 2085 reserved port number. |
| 2086 | |
| 2087 @item sort | |
| 2088 Used in @code{ls}. | |
| 2089 | |
| 2090 @item source | |
| 2091 @samp{-W source} in @code{gawk}. | |
| 2092 | |
| 2093 @item sparse | |
| 2094 @samp{-S} in @code{tar}. | |
| 2095 | |
| 2096 @item speed-large-files | |
| 2097 @samp{-H} in @code{diff}. | |
| 2098 | |
| 2099 @item split-at | |
| 2100 @samp{-E} in @code{unshar}. | |
| 2101 | |
| 2102 @item split-size-limit | |
| 2103 @samp{-L} in @code{shar}. | |
| 2104 | |
| 2105 @item squeeze-blank | |
| 2106 @samp{-s} in @code{cat}. | |
| 2107 | |
| 2108 @item start-delete | |
| 2109 @samp{-w} in @code{wdiff}. | |
| 2110 | |
| 2111 @item start-insert | |
| 2112 @samp{-y} in @code{wdiff}. | |
| 2113 | |
| 2114 @item starting-file | |
| 2115 Used in @code{tar} and @code{diff} to specify which file within | |
| 2116 a directory to start processing with. | |
| 2117 | |
| 2118 @item statistics | |
| 2119 @samp{-s} in @code{wdiff}. | |
| 2120 | |
| 2121 @item stdin-file-list | |
| 2122 @samp{-S} in @code{shar}. | |
| 2123 | |
| 2124 @item stop | |
| 10199 | 2125 @samp{-S} in @code{make}. |
| 4958 | 2126 |
| 2127 @item strict | |
| 2128 @samp{-s} in @code{recode}. | |
| 2129 | |
| 2130 @item strip | |
| 2131 @samp{-s} in @code{install}. | |
| 2132 | |
| 2133 @item strip-all | |
| 2134 @samp{-s} in @code{strip}. | |
| 2135 | |
| 2136 @item strip-debug | |
| 2137 @samp{-S} in @code{strip}. | |
| 2138 | |
| 2139 @item submitter | |
| 2140 @samp{-s} in @code{shar}. | |
| 2141 | |
| 2142 @item suffix | |
| 2143 @samp{-S} in @code{cp}, @code{ln}, @code{mv}. | |
| 2144 | |
| 2145 @item suffix-format | |
| 2146 @samp{-b} in @code{csplit}. | |
| 2147 | |
| 2148 @item sum | |
| 2149 @samp{-s} in @code{gprof}. | |
| 2150 | |
| 2151 @item summarize | |
| 2152 @samp{-s} in @code{du}. | |
| 2153 | |
| 2154 @item symbolic | |
| 2155 @samp{-s} in @code{ln}. | |
| 2156 | |
| 2157 @item symbols | |
| 2158 Used in GDB and @code{objdump}. | |
| 2159 | |
| 2160 @item synclines | |
| 2161 @samp{-s} in @code{m4}. | |
| 2162 | |
| 2163 @item sysname | |
| 2164 @samp{-s} in @code{uname}. | |
| 2165 | |
| 2166 @item tabs | |
| 2167 @samp{-t} in @code{expand} and @code{unexpand}. | |
| 2168 | |
| 2169 @item tabsize | |
| 2170 @samp{-T} in @code{ls}. | |
| 2171 | |
| 2172 @item terminal | |
| 2173 @samp{-T} in @code{tput} and @code{ul}. | |
| 2174 @samp{-t} in @code{wdiff}. | |
| 2175 | |
| 2176 @item text | |
| 2177 @samp{-a} in @code{diff}. | |
| 2178 | |
| 2179 @item text-files | |
| 2180 @samp{-T} in @code{shar}. | |
| 2181 | |
| 2182 @item time | |
| 2183 Used in @code{ls} and @code{touch}. | |
| 2184 | |
| 2185 @item timeout | |
| 2186 Specify how long to wait before giving up on some operation. | |
| 2187 | |
| 2188 @item to-stdout | |
| 2189 @samp{-O} in @code{tar}. | |
| 2190 | |
| 2191 @item total | |
| 2192 @samp{-c} in @code{du}. | |
| 2193 | |
| 2194 @item touch | |
| 10199 | 2195 @samp{-t} in @code{make}, @code{ranlib}, and @code{recode}. |
| 4958 | 2196 |
| 2197 @item trace | |
| 2198 @samp{-t} in @code{m4}. | |
| 2199 | |
| 2200 @item traditional | |
| 2201 @samp{-t} in @code{hello}; | |
| 2202 @samp{-W traditional} in @code{gawk}; | |
| 2203 @samp{-G} in @code{ed}, @code{m4}, and @code{ptx}. | |
| 2204 | |
| 2205 @item tty | |
| 2206 Used in GDB. | |
| 2207 | |
| 2208 @item typedefs | |
| 2209 @samp{-t} in @code{ctags}. | |
| 2210 | |
| 2211 @item typedefs-and-c++ | |
| 2212 @samp{-T} in @code{ctags}. | |
| 2213 | |
| 2214 @item typeset-mode | |
| 2215 @samp{-t} in @code{ptx}. | |
| 2216 | |
| 2217 @item uncompress | |
| 2218 @samp{-z} in @code{tar}. | |
| 2219 | |
| 2220 @item unconditional | |
| 2221 @samp{-u} in @code{cpio}. | |
| 2222 | |
| 2223 @item undefine | |
| 2224 @samp{-U} in @code{m4}. | |
| 2225 | |
| 2226 @item undefined-only | |
| 2227 @samp{-u} in @code{nm}. | |
| 2228 | |
| 2229 @item update | |
| 2230 @samp{-u} in @code{cp}, @code{ctags}, @code{mv}, @code{tar}. | |
| 2231 | |
| 2232 @item usage | |
| 2233 Used in @code{gawk}; same as @samp{--help}. | |
| 2234 | |
| 2235 @item uuencode | |
| 2236 @samp{-B} in @code{shar}. | |
| 2237 | |
| 2238 @item vanilla-operation | |
| 2239 @samp{-V} in @code{shar}. | |
| 2240 | |
| 2241 @item verbose | |
| 2242 Print more information about progress. Many programs support this. | |
| 2243 | |
| 2244 @item verify | |
| 2245 @samp{-W} in @code{tar}. | |
| 2246 | |
| 2247 @item version | |
| 2248 Print the version number. | |
| 2249 | |
| 2250 @item version-control | |
| 2251 @samp{-V} in @code{cp}, @code{ln}, @code{mv}. | |
| 2252 | |
| 2253 @item vgrind | |
| 2254 @samp{-v} in @code{ctags}. | |
| 2255 | |
| 2256 @item volume | |
| 2257 @samp{-V} in @code{tar}. | |
| 2258 | |
| 2259 @item what-if | |
| 10199 | 2260 @samp{-W} in @code{make}. |
| 4958 | 2261 |
| 2262 @item whole-size-limit | |
| 2263 @samp{-l} in @code{shar}. | |
| 2264 | |
| 2265 @item width | |
| 2266 @samp{-w} in @code{ls} and @code{ptx}. | |
| 2267 | |
| 2268 @item word-regexp | |
| 2269 @samp{-W} in @code{ptx}. | |
| 2270 | |
| 2271 @item writable | |
| 2272 @samp{-T} in @code{who}. | |
| 2273 | |
| 2274 @item zeros | |
| 2275 @samp{-z} in @code{gprof}. | |
| 2276 @end table | |
| 2277 | |
| 10742 | 2278 @node OID Allocations |
| 2279 @section OID Allocations | |
| 2280 @cindex OID allocations for GNU | |
| 2281 @cindex SNMP | |
| 2282 @cindex LDAP | |
| 2283 @cindex X.509 | |
| 2284 | |
| 2285 The OID (object identifier) 1.3.6.1.4.1.11591 has been assigned to the | |
| 2286 GNU Project (thanks to Werner Koch). These are used for SNMP, LDAP, | |
| 2287 X.509 certificates, and so on. The web site | |
| 2288 @url{http://www.alvestrand.no/objectid} has a (voluntary) listing of | |
| 2289 many OID assignments. | |
| 2290 | |
| 2291 If you need a new slot for your GNU package, write | |
| 2292 @email{maintainers@@gnu.org}. Here is a list of arcs currently | |
| 2293 assigned: | |
| 2294 | |
| 2295 @example | |
| 2296 @include gnu-oids.texi | |
| 2297 @end example | |
| 2298 | |
| 2299 | |
| 4958 | 2300 @node Memory Usage |
| 2301 @section Memory Usage | |
| 2302 @cindex memory usage | |
| 2303 | |
| 2304 If a program typically uses just a few meg of memory, don't bother making any | |
| 2305 effort to reduce memory usage. For example, if it is impractical for | |
| 2306 other reasons to operate on files more than a few meg long, it is | |
| 7663 | 2307 reasonable to read entire input files into memory to operate on them. |
| 4958 | 2308 |
| 2309 However, for programs such as @code{cat} or @code{tail}, that can | |
| 2310 usefully operate on very large files, it is important to avoid using a | |
| 2311 technique that would artificially limit the size of files it can handle. | |
| 2312 If a program works by lines and could be applied to arbitrary | |
| 2313 user-supplied input files, it should keep only a line in memory, because | |
| 2314 this is not very hard and users will want to be able to operate on input | |
| 7663 | 2315 files that are bigger than will fit in memory all at once. |
| 4958 | 2316 |
| 2317 If your program creates complicated data structures, just make them in | |
| 7663 | 2318 memory and give a fatal error if @code{malloc} returns zero. |
| 4958 | 2319 |
| 13659 | 2320 @pindex valgrind |
| 2321 @cindex memory leak | |
| 14719 | 2322 Memory analysis tools such as @command{valgrind} can be useful, but |
| 13659 | 2323 don't complicate a program merely to avoid their false alarms. For |
| 2324 example, if memory is used until just before a process exits, don't | |
| 14719 | 2325 free it simply to silence such a tool. |
| 2326 | |
| 13659 | 2327 |
| 4958 | 2328 @node File Usage |
| 2329 @section File Usage | |
| 2330 @cindex file usage | |
| 2331 | |
| 2332 Programs should be prepared to operate when @file{/usr} and @file{/etc} | |
| 2333 are read-only file systems. Thus, if the program manages log files, | |
| 2334 lock files, backup files, score files, or any other files which are | |
| 2335 modified for internal purposes, these files should not be stored in | |
| 2336 @file{/usr} or @file{/etc}. | |
| 2337 | |
| 2338 There are two exceptions. @file{/etc} is used to store system | |
| 2339 configuration information; it is reasonable for a program to modify | |
| 2340 files in @file{/etc} when its job is to update the system configuration. | |
| 2341 Also, if the user explicitly asks to modify one file in a directory, it | |
| 2342 is reasonable for the program to store other files in the same | |
| 2343 directory. | |
| 2344 | |
| 2345 @node Writing C | |
| 2346 @chapter Making The Best Use of C | |
| 2347 | |
| 5301 | 2348 This chapter provides advice on how best to use the C language |
| 4958 | 2349 when writing GNU software. |
| 2350 | |
| 2351 @menu | |
| 9115 | 2352 * Formatting:: Formatting your source code. |
| 2353 * Comments:: Commenting your work. | |
| 2354 * Syntactic Conventions:: Clean use of C constructs. | |
| 2355 * Names:: Naming variables, functions, and files. | |
| 2356 * System Portability:: Portability among different operating systems. | |
| 2357 * CPU Portability:: Supporting the range of CPU types. | |
| 2358 * System Functions:: Portability and ``standard'' library functions. | |
| 2359 * Internationalization:: Techniques for internationalization. | |
| 6066 | 2360 * Character Set:: Use ASCII by default. |
| 16202 | 2361 * Quote Characters:: Use "..." or '...' in the C locale. |
| 4958 | 2362 * Mmap:: How you can safely use @code{mmap}. |
| 2363 @end menu | |
| 2364 | |
| 2365 @node Formatting | |
| 2366 @section Formatting Your Source Code | |
| 2367 @cindex formatting source code | |
| 2368 | |
| 2369 @cindex open brace | |
| 2370 @cindex braces, in C source | |
| 16773 | 2371 @cindex function definitions, formatting |
| 4958 | 2372 It is important to put the open-brace that starts the body of a C |
| 7703 | 2373 function in column one, so that they will start a defun. Several |
| 2374 tools look for open-braces in column one to find the beginnings of C | |
| 2375 functions. These tools will not work on code not formatted that way. | |
| 2376 | |
| 2377 Avoid putting open-brace, open-parenthesis or open-bracket in column | |
| 2378 one when they are inside a function, so that they won't start a defun. | |
| 2379 The open-brace that starts a @code{struct} body can go in column one | |
| 2380 if you find it useful to treat that definition as a defun. | |
| 4958 | 2381 |
| 2382 It is also important for function definitions to start the name of the | |
| 6498 | 2383 function in column one. This helps people to search for function |
| 4958 | 2384 definitions, and may also help certain tools recognize them. Thus, |
| 5909 | 2385 using Standard C syntax, the format is this: |
| 4958 | 2386 |
| 2387 @example | |
| 2388 static char * | |
| 5909 | 2389 concat (char *s1, char *s2) |
| 2390 @{ | |
| 4958 | 2391 @dots{} |
| 2392 @} | |
| 2393 @end example | |
| 2394 | |
| 2395 @noindent | |
| 6725 | 2396 or, if you want to use traditional C syntax, format the definition like |
| 4958 | 2397 this: |
| 2398 | |
| 2399 @example | |
| 2400 static char * | |
| 6498 | 2401 concat (s1, s2) /* Name starts in column one here */ |
| 5909 | 2402 char *s1, *s2; |
| 6498 | 2403 @{ /* Open brace in column one here */ |
| 4958 | 2404 @dots{} |
| 2405 @} | |
| 2406 @end example | |
| 2407 | |
| 2408 In Standard C, if the arguments don't fit nicely on one line, | |
| 2409 split it like this: | |
| 2410 | |
| 2411 @example | |
| 2412 int | |
| 2413 lots_of_args (int an_integer, long a_long, short a_short, | |
| 2414 double a_double, float a_float) | |
| 2415 @dots{} | |
| 2416 @end example | |
| 2417 | |
| 16773 | 2418 @cindex @code{struct} types, formatting |
| 2419 @cindex @code{enum} types, formatting | |
| 2420 For @code{struct} and @code{enum} types, likewise put the braces in | |
| 2421 column one, unless the whole contents fits on one line: | |
| 2422 | |
| 2423 @example | |
| 2424 struct foo | |
| 2425 @{ | |
| 2426 int a, b; | |
| 2427 @} | |
| 2428 @exdent @r{or} | |
| 2429 struct foo @{ int a, b; @} | |
| 2430 @end example | |
| 2431 | |
| 4958 | 2432 The rest of this section gives our recommendations for other aspects of |
| 2433 C formatting style, which is also the default style of the @code{indent} | |
| 2434 program in version 1.2 and newer. It corresponds to the options | |
| 2435 | |
| 2436 @smallexample | |
| 2437 -nbad -bap -nbc -bbo -bl -bli2 -bls -ncdb -nce -cp1 -cs -di2 | |
| 2438 -ndj -nfc1 -nfca -hnl -i2 -ip5 -lp -pcs -psl -nsc -nsob | |
| 2439 @end smallexample | |
| 2440 | |
| 2441 We don't think of these recommendations as requirements, because it | |
| 2442 causes no problems for users if two different programs have different | |
| 2443 formatting styles. | |
| 2444 | |
| 2445 But whatever style you use, please use it consistently, since a mixture | |
| 2446 of styles within one program tends to look ugly. If you are | |
| 2447 contributing changes to an existing program, please follow the style of | |
| 2448 that program. | |
| 2449 | |
| 2450 For the body of the function, our recommended style looks like this: | |
| 2451 | |
| 2452 @example | |
| 2453 if (x < foo (y, z)) | |
| 2454 haha = bar[4] + 5; | |
| 2455 else | |
| 2456 @{ | |
| 2457 while (z) | |
| 2458 @{ | |
| 2459 haha += foo (z, z); | |
| 2460 z--; | |
| 2461 @} | |
| 2462 return ++x + bar (); | |
| 2463 @} | |
| 2464 @end example | |
| 2465 | |
| 2466 @cindex spaces before open-paren | |
| 2467 We find it easier to read a program when it has spaces before the | |
| 2468 open-parentheses and after the commas. Especially after the commas. | |
| 2469 | |
| 2470 When you split an expression into multiple lines, split it | |
| 2471 before an operator, not after one. Here is the right way: | |
| 2472 | |
| 2473 @cindex expressions, splitting | |
| 2474 @example | |
| 2475 if (foo_this_is_long && bar > win (x, y, z) | |
| 2476 && remaining_condition) | |
| 2477 @end example | |
| 2478 | |
| 2479 Try to avoid having two operators of different precedence at the same | |
| 2480 level of indentation. For example, don't write this: | |
| 2481 | |
| 2482 @example | |
| 2483 mode = (inmode[j] == VOIDmode | |
| 2484 || GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]) | |
| 2485 ? outmode[j] : inmode[j]); | |
| 2486 @end example | |
| 2487 | |
| 2488 Instead, use extra parentheses so that the indentation shows the nesting: | |
| 2489 | |
| 2490 @example | |
| 2491 mode = ((inmode[j] == VOIDmode | |
| 2492 || (GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]))) | |
| 2493 ? outmode[j] : inmode[j]); | |
| 2494 @end example | |
| 2495 | |
| 2496 Insert extra parentheses so that Emacs will indent the code properly. | |
| 2497 For example, the following indentation looks nice if you do it by hand, | |
| 2498 | |
| 2499 @example | |
| 2500 v = rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 | |
| 2501 + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000; | |
| 2502 @end example | |
| 2503 | |
| 2504 @noindent | |
| 2505 but Emacs would alter it. Adding a set of parentheses produces | |
| 2506 something that looks equally nice, and which Emacs will preserve: | |
| 2507 | |
| 2508 @example | |
| 2509 v = (rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 | |
| 2510 + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000); | |
| 2511 @end example | |
| 2512 | |
| 2513 Format do-while statements like this: | |
| 2514 | |
| 2515 @example | |
| 2516 do | |
| 2517 @{ | |
| 2518 a = foo (a); | |
| 2519 @} | |
| 2520 while (a > 0); | |
| 2521 @end example | |
| 2522 | |
| 2523 @cindex formfeed | |
| 2524 @cindex control-L | |
| 2525 Please use formfeed characters (control-L) to divide the program into | |
| 2526 pages at logical places (but not within a function). It does not matter | |
| 2527 just how long the pages are, since they do not have to fit on a printed | |
| 2528 page. The formfeeds should appear alone on lines by themselves. | |
| 2529 | |
| 2530 @node Comments | |
| 2531 @section Commenting Your Work | |
| 2532 @cindex commenting | |
| 2533 | |
| 2534 Every program should start with a comment saying briefly what it is for. | |
| 6066 | 2535 Example: @samp{fmt - filter for simple filling of text}. This comment |
| 2536 should be at the top of the source file containing the @samp{main} | |
| 2537 function of the program. | |
| 2538 | |
| 2539 Also, please write a brief comment at the start of each source file, | |
| 2540 with the file name and a line or two about the overall purpose of the | |
| 2541 file. | |
| 4958 | 2542 |
| 2543 Please write the comments in a GNU program in English, because English | |
| 2544 is the one language that nearly all programmers in all countries can | |
| 2545 read. If you do not write English well, please write comments in | |
| 2546 English as well as you can, then ask other people to help rewrite them. | |
| 2547 If you can't write comments in English, please find someone to work with | |
| 2548 you and translate your comments into English. | |
| 2549 | |
| 2550 Please put a comment on each function saying what the function does, | |
| 2551 what sorts of arguments it gets, and what the possible values of | |
| 2552 arguments mean and are used for. It is not necessary to duplicate in | |
| 2553 words the meaning of the C argument declarations, if a C type is being | |
| 2554 used in its customary fashion. If there is anything nonstandard about | |
| 2555 its use (such as an argument of type @code{char *} which is really the | |
| 2556 address of the second character of a string, not the first), or any | |
| 2557 possible values that would not work the way one would expect (such as, | |
| 2558 that strings containing newlines are not guaranteed to work), be sure | |
| 2559 to say so. | |
| 2560 | |
| 2561 Also explain the significance of the return value, if there is one. | |
| 2562 | |
| 2563 Please put two spaces after the end of a sentence in your comments, so | |
| 2564 that the Emacs sentence commands will work. Also, please write | |
| 2565 complete sentences and capitalize the first word. If a lower-case | |
| 2566 identifier comes at the beginning of a sentence, don't capitalize it! | |
| 2567 Changing the spelling makes it a different identifier. If you don't | |
| 2568 like starting a sentence with a lower case letter, write the sentence | |
| 2569 differently (e.g., ``The identifier lower-case is @dots{}''). | |
| 2570 | |
| 2571 The comment on a function is much clearer if you use the argument | |
| 2572 names to speak about the argument values. The variable name itself | |
| 2573 should be lower case, but write it in upper case when you are speaking | |
| 2574 about the value rather than the variable itself. Thus, ``the inode | |
| 2575 number NODE_NUM'' rather than ``an inode''. | |
| 2576 | |
| 2577 There is usually no purpose in restating the name of the function in | |
| 16773 | 2578 the comment before it, because readers can see that for themselves. |
| 4958 | 2579 There might be an exception when the comment is so long that the function |
| 2580 itself would be off the bottom of the screen. | |
| 2581 | |
| 2582 There should be a comment on each static variable as well, like this: | |
| 2583 | |
| 2584 @example | |
| 2585 /* Nonzero means truncate lines in the display; | |
| 2586 zero means continue them. */ | |
| 2587 int truncate_lines; | |
| 2588 @end example | |
| 2589 | |
| 2590 @cindex conditionals, comments for | |
| 2591 @cindex @code{#endif}, commenting | |
| 2592 Every @samp{#endif} should have a comment, except in the case of short | |
| 2593 conditionals (just a few lines) that are not nested. The comment should | |
| 2594 state the condition of the conditional that is ending, @emph{including | |
| 2595 its sense}. @samp{#else} should have a comment describing the condition | |
| 2596 @emph{and sense} of the code that follows. For example: | |
| 2597 | |
| 2598 @example | |
| 2599 @group | |
| 2600 #ifdef foo | |
| 2601 @dots{} | |
| 2602 #else /* not foo */ | |
| 2603 @dots{} | |
| 2604 #endif /* not foo */ | |
| 2605 @end group | |
| 2606 @group | |
| 2607 #ifdef foo | |
| 2608 @dots{} | |
| 2609 #endif /* foo */ | |
| 2610 @end group | |
| 2611 @end example | |
| 2612 | |
| 2613 @noindent | |
| 2614 but, by contrast, write the comments this way for a @samp{#ifndef}: | |
| 2615 | |
| 2616 @example | |
| 2617 @group | |
| 2618 #ifndef foo | |
| 2619 @dots{} | |
| 2620 #else /* foo */ | |
| 2621 @dots{} | |
| 2622 #endif /* foo */ | |
| 2623 @end group | |
| 2624 @group | |
| 2625 #ifndef foo | |
| 2626 @dots{} | |
| 2627 #endif /* not foo */ | |
| 2628 @end group | |
| 2629 @end example | |
| 2630 | |
| 2631 @node Syntactic Conventions | |
| 2632 @section Clean Use of C Constructs | |
| 2633 @cindex syntactic conventions | |
| 2634 | |
| 2635 @cindex implicit @code{int} | |
| 2636 @cindex function argument, declaring | |
| 2637 Please explicitly declare the types of all objects. For example, you | |
| 2638 should explicitly declare all arguments to functions, and you should | |
| 2639 declare functions to return @code{int} rather than omitting the | |
| 2640 @code{int}. | |
| 2641 | |
| 2642 @cindex compiler warnings | |
| 2643 @cindex @samp{-Wall} compiler option | |
| 2644 Some programmers like to use the GCC @samp{-Wall} option, and change the | |
| 2645 code whenever it issues a warning. If you want to do this, then do. | |
| 2646 Other programmers prefer not to use @samp{-Wall}, because it gives | |
| 2647 warnings for valid and legitimate code which they do not want to change. | |
| 2648 If you want to do this, then do. The compiler should be your servant, | |
| 2649 not your master. | |
| 2650 | |
| 13659 | 2651 @pindex clang |
| 2652 @pindex lint | |
| 2653 Don't make the program ugly just to placate static analysis tools such | |
| 2654 as @command{lint}, @command{clang}, and GCC with extra warnings | |
| 2655 options such as @option{-Wconversion} and @option{-Wundef}. These | |
| 2656 tools can help find bugs and unclear code, but they can also generate | |
| 16673 | 2657 so many false alarms that it hurts readability to silence them with |
| 2658 unnecessary casts, wrappers, and other complications. For example, | |
| 2659 please don't insert casts to @code{void} or calls to do-nothing | |
| 2660 functions merely to pacify a lint checker. | |
| 13659 | 2661 |
| 4958 | 2662 Declarations of external functions and functions to appear later in the |
| 2663 source file should all go in one place near the beginning of the file | |
| 2664 (somewhere before the first function definition in the file), or else | |
| 2665 should go in a header file. Don't put @code{extern} declarations inside | |
| 2666 functions. | |
| 2667 | |
| 2668 @cindex temporary variables | |
| 2669 It used to be common practice to use the same local variables (with | |
| 2670 names like @code{tem}) over and over for different values within one | |
| 2671 function. Instead of doing this, it is better to declare a separate local | |
| 2672 variable for each distinct purpose, and give it a name which is | |
| 2673 meaningful. This not only makes programs easier to understand, it also | |
| 2674 facilitates optimization by good compilers. You can also move the | |
| 2675 declaration of each local variable into the smallest scope that includes | |
| 2676 all its uses. This makes the program even cleaner. | |
| 2677 | |
| 2678 Don't use local variables or parameters that shadow global identifiers. | |
| 13659 | 2679 GCC's @samp{-Wshadow} option can detect this problem. |
| 4958 | 2680 |
| 2681 @cindex multiple variables in a line | |
| 2682 Don't declare multiple variables in one declaration that spans lines. | |
| 2683 Start a new declaration on each line, instead. For example, instead | |
| 2684 of this: | |
| 2685 | |
| 2686 @example | |
| 2687 @group | |
| 2688 int foo, | |
| 2689 bar; | |
| 2690 @end group | |
| 2691 @end example | |
| 2692 | |
| 2693 @noindent | |
| 2694 write either this: | |
| 2695 | |
| 2696 @example | |
| 2697 int foo, bar; | |
| 2698 @end example | |
| 2699 | |
| 2700 @noindent | |
| 2701 or this: | |
| 2702 | |
| 2703 @example | |
| 2704 int foo; | |
| 2705 int bar; | |
| 2706 @end example | |
| 2707 | |
| 2708 @noindent | |
| 2709 (If they are global variables, each should have a comment preceding it | |
| 2710 anyway.) | |
| 2711 | |
| 2712 When you have an @code{if}-@code{else} statement nested in another | |
| 2713 @code{if} statement, always put braces around the @code{if}-@code{else}. | |
| 2714 Thus, never write like this: | |
| 2715 | |
| 2716 @example | |
| 2717 if (foo) | |
| 2718 if (bar) | |
| 2719 win (); | |
| 2720 else | |
| 2721 lose (); | |
| 2722 @end example | |
| 2723 | |
| 2724 @noindent | |
| 2725 always like this: | |
| 2726 | |
| 2727 @example | |
| 2728 if (foo) | |
| 2729 @{ | |
| 2730 if (bar) | |
| 2731 win (); | |
| 2732 else | |
| 2733 lose (); | |
| 2734 @} | |
| 2735 @end example | |
| 2736 | |
| 2737 If you have an @code{if} statement nested inside of an @code{else} | |
| 2738 statement, either write @code{else if} on one line, like this, | |
| 2739 | |
| 2740 @example | |
| 2741 if (foo) | |
| 2742 @dots{} | |
| 2743 else if (bar) | |
| 2744 @dots{} | |
| 2745 @end example | |
| 2746 | |
| 2747 @noindent | |
| 2748 with its @code{then}-part indented like the preceding @code{then}-part, | |
| 2749 or write the nested @code{if} within braces like this: | |
| 2750 | |
| 2751 @example | |
| 2752 if (foo) | |
| 2753 @dots{} | |
| 2754 else | |
| 2755 @{ | |
| 2756 if (bar) | |
| 2757 @dots{} | |
| 2758 @} | |
| 2759 @end example | |
| 2760 | |
| 2761 Don't declare both a structure tag and variables or typedefs in the | |
| 2762 same declaration. Instead, declare the structure tag separately | |
| 2763 and then use it to declare the variables or typedefs. | |
| 2764 | |
| 7663 | 2765 Try to avoid assignments inside @code{if}-conditions (assignments |
| 2766 inside @code{while}-conditions are ok). For example, don't write | |
| 2767 this: | |
| 4958 | 2768 |
| 2769 @example | |
| 2770 if ((foo = (char *) malloc (sizeof *foo)) == 0) | |
| 2771 fatal ("virtual memory exhausted"); | |
| 2772 @end example | |
| 2773 | |
| 2774 @noindent | |
| 2775 instead, write this: | |
| 2776 | |
| 2777 @example | |
| 2778 foo = (char *) malloc (sizeof *foo); | |
| 2779 if (foo == 0) | |
| 2780 fatal ("virtual memory exhausted"); | |
| 2781 @end example | |
| 2782 | |
| 13659 | 2783 This example uses zero without a cast as a null pointer constant. |
| 2784 This is perfectly fine, except that a cast is needed when calling a | |
| 2785 varargs function or when using @code{sizeof}. | |
| 4958 | 2786 |
| 2787 @node Names | |
| 2788 @section Naming Variables, Functions, and Files | |
| 2789 | |
| 2790 @cindex names of variables, functions, and files | |
| 2791 The names of global variables and functions in a program serve as | |
| 2792 comments of a sort. So don't choose terse names---instead, look for | |
| 2793 names that give useful information about the meaning of the variable or | |
| 2794 function. In a GNU program, names should be English, like other | |
| 2795 comments. | |
| 2796 | |
| 2797 Local variable names can be shorter, because they are used only within | |
| 2798 one context, where (presumably) comments explain their purpose. | |
| 2799 | |
| 2800 Try to limit your use of abbreviations in symbol names. It is ok to | |
| 2801 make a few abbreviations, explain what they mean, and then use them | |
| 2802 frequently, but don't use lots of obscure abbreviations. | |
| 2803 | |
| 2804 Please use underscores to separate words in a name, so that the Emacs | |
| 2805 word commands can be useful within them. Stick to lower case; reserve | |
| 2806 upper case for macros and @code{enum} constants, and for name-prefixes | |
| 2807 that follow a uniform convention. | |
| 2808 | |
| 2809 For example, you should use names like @code{ignore_space_change_flag}; | |
| 2810 don't use names like @code{iCantReadThis}. | |
| 2811 | |
| 2812 Variables that indicate whether command-line options have been | |
| 2813 specified should be named after the meaning of the option, not after | |
| 2814 the option-letter. A comment should state both the exact meaning of | |
| 2815 the option and its letter. For example, | |
| 2816 | |
| 2817 @example | |
| 2818 @group | |
| 2819 /* Ignore changes in horizontal whitespace (-b). */ | |
| 2820 int ignore_space_change_flag; | |
| 2821 @end group | |
| 2822 @end example | |
| 2823 | |
| 2824 When you want to define names with constant integer values, use | |
| 2825 @code{enum} rather than @samp{#define}. GDB knows about enumeration | |
| 2826 constants. | |
| 2827 | |
| 2828 @cindex file-name limitations | |
| 2829 @pindex doschk | |
| 2830 You might want to make sure that none of the file names would conflict | |
| 6498 | 2831 if the files were loaded onto an MS-DOS file system which shortens the |
| 4958 | 2832 names. You can use the program @code{doschk} to test for this. |
| 2833 | |
| 2834 Some GNU programs were designed to limit themselves to file names of 14 | |
| 2835 characters or less, to avoid file name conflicts if they are read into | |
| 2836 older System V systems. Please preserve this feature in the existing | |
| 2837 GNU programs that have it, but there is no need to do this in new GNU | |
| 2838 programs. @code{doschk} also reports file names longer than 14 | |
| 2839 characters. | |
| 2840 | |
| 14502 | 2841 |
| 4958 | 2842 @node System Portability |
| 2843 @section Portability between System Types | |
| 2844 @cindex portability, between system types | |
| 2845 | |
| 2846 In the Unix world, ``portability'' refers to porting to different Unix | |
| 2847 versions. For a GNU program, this kind of portability is desirable, but | |
| 2848 not paramount. | |
| 2849 | |
| 2850 The primary purpose of GNU software is to run on top of the GNU kernel, | |
| 17256 | 2851 compiled with the GNU C compiler, on various types of CPU. So the |
| 4958 | 2852 kinds of portability that are absolutely necessary are quite limited. |
| 2853 But it is important to support Linux-based GNU systems, since they | |
| 2854 are the form of GNU that is popular. | |
| 2855 | |
| 2856 Beyond that, it is good to support the other free operating systems | |
| 2857 (*BSD), and it is nice to support other Unix-like systems if you want | |
| 2858 to. Supporting a variety of Unix-like systems is desirable, although | |
| 2859 not paramount. It is usually not too hard, so you may as well do it. | |
| 2860 But you don't have to consider it an obligation, if it does turn out to | |
| 2861 be hard. | |
| 2862 | |
| 2863 @pindex autoconf | |
| 2864 The easiest way to achieve portability to most Unix-like systems is to | |
| 2865 use Autoconf. It's unlikely that your program needs to know more | |
| 2866 information about the host platform than Autoconf can provide, simply | |
| 2867 because most of the programs that need such knowledge have already been | |
| 2868 written. | |
| 2869 | |
| 2870 Avoid using the format of semi-internal data bases (e.g., directories) | |
| 2871 when there is a higher-level alternative (@code{readdir}). | |
| 2872 | |
| 17256 | 2873 @cindex non-POSIX systems, and portability |
| 6066 | 2874 As for systems that are not like Unix, such as MSDOS, Windows, VMS, MVS, |
| 2875 and older Macintosh systems, supporting them is often a lot of work. | |
| 2876 When that is the case, it is better to spend your time adding features | |
| 2877 that will be useful on GNU and GNU/Linux, rather than on supporting | |
| 2878 other incompatible systems. | |
| 4958 | 2879 |
| 2880 If you do support Windows, please do not abbreviate it as ``win''. In | |
| 2881 hacker terminology, calling something a ``win'' is a form of praise. | |
| 2882 You're free to praise Microsoft Windows on your own if you want, but | |
| 2883 please don't do this in GNU packages. Instead of abbreviating | |
|
9485
4e0536363af3
* doc/fdl.texi, doc/gpl-3.0.texi, doc/lgpl-3.0.texi:
Ralf Wildenhues <Ralf.Wildenhues@gmx.de>
parents:
9204
diff
changeset
|
2884 ``Windows'' to ``win'', you can write it in full or abbreviate it to |
| 4958 | 2885 ``woe'' or ``w''. In GNU Emacs, for instance, we use @samp{w32} in |
| 2886 file names of Windows-specific files, but the macro for Windows | |
| 2887 conditionals is called @code{WINDOWSNT}. | |
| 2888 | |
| 2889 It is a good idea to define the ``feature test macro'' | |
| 2890 @code{_GNU_SOURCE} when compiling your C files. When you compile on GNU | |
| 2891 or GNU/Linux, this will enable the declarations of GNU library extension | |
| 2892 functions, and that will usually give you a compiler error message if | |
| 2893 you define the same function names in some other way in your program. | |
| 2894 (You don't have to actually @emph{use} these functions, if you prefer | |
| 2895 to make the program more portable to other systems.) | |
| 2896 | |
| 2897 But whether or not you use these GNU extensions, you should avoid | |
| 2898 using their names for any other meanings. Doing so would make it hard | |
| 2899 to move your code into other GNU programs. | |
| 2900 | |
| 2901 @node CPU Portability | |
| 17256 | 2902 @section Portability between CPUs |
| 4958 | 2903 |
| 2904 @cindex data types, and portability | |
| 2905 @cindex portability, and data types | |
| 17256 | 2906 Even GNU systems will differ because of differences among CPU |
| 4958 | 2907 types---for example, difference in byte ordering and alignment |
| 2908 requirements. It is absolutely essential to handle these differences. | |
| 2909 However, don't make any effort to cater to the possibility that an | |
| 2910 @code{int} will be less than 32 bits. We don't support 16-bit machines | |
| 2911 in GNU. | |
| 2912 | |
| 2913 Similarly, don't make any effort to cater to the possibility that | |
| 2914 @code{long} will be smaller than predefined types like @code{size_t}. | |
| 2915 For example, the following code is ok: | |
| 2916 | |
| 2917 @example | |
| 2918 printf ("size = %lu\n", (unsigned long) sizeof array); | |
| 2919 printf ("diff = %ld\n", (long) (pointer2 - pointer1)); | |
| 2920 @end example | |
| 2921 | |
| 2922 1989 Standard C requires this to work, and we know of only one | |
| 14502 | 2923 counterexample: 64-bit programs on Microsoft Windows. We will leave |
| 2924 it to those who want to port GNU programs to that environment to | |
| 2925 figure out how to do it. | |
| 4958 | 2926 |
| 2927 Predefined file-size types like @code{off_t} are an exception: they are | |
| 2928 longer than @code{long} on many platforms, so code like the above won't | |
| 2929 work with them. One way to print an @code{off_t} value portably is to | |
| 2930 print its digits yourself, one by one. | |
| 2931 | |
| 2932 Don't assume that the address of an @code{int} object is also the | |
| 2933 address of its least-significant byte. This is false on big-endian | |
| 2934 machines. Thus, don't make the following mistake: | |
| 2935 | |
| 2936 @example | |
| 2937 int c; | |
| 2938 @dots{} | |
| 7663 | 2939 while ((c = getchar ()) != EOF) |
| 2940 write (file_descriptor, &c, 1); | |
| 2941 @end example | |
| 2942 | |
| 2943 @noindent Instead, use @code{unsigned char} as follows. (The @code{unsigned} | |
| 2944 is for portability to unusual systems where @code{char} is signed and | |
| 2945 where there is integer overflow checking.) | |
| 2946 | |
| 2947 @example | |
| 2948 int c; | |
| 2949 while ((c = getchar ()) != EOF) | |
| 2950 @{ | |
| 2951 unsigned char u = c; | |
| 2952 write (file_descriptor, &u, 1); | |
| 2953 @} | |
| 4958 | 2954 @end example |
| 2955 | |
| 2956 @cindex casting pointers to integers | |
| 2957 Avoid casting pointers to integers if you can. Such casts greatly | |
| 2958 reduce portability, and in most programs they are easy to avoid. In the | |
| 2959 cases where casting pointers to integers is essential---such as, a Lisp | |
| 2960 interpreter which stores type information as well as an address in one | |
| 2961 word---you'll have to make explicit provisions to handle different word | |
| 2962 sizes. You will also need to make provision for systems in which the | |
| 2963 normal range of addresses you can get from @code{malloc} starts far away | |
| 2964 from zero. | |
| 2965 | |
| 14502 | 2966 |
| 4958 | 2967 @node System Functions |
| 2968 @section Calling System Functions | |
| 14502 | 2969 |
| 2970 @cindex C library functions, and portability | |
| 2971 @cindex POSIX functions, and portability | |
| 4958 | 2972 @cindex library functions, and portability |
| 2973 @cindex portability, and library functions | |
| 2974 | |
| 14502 | 2975 Historically, C implementations differed substantially, and many |
| 2976 systems lacked a full implementation of ANSI/ISO C89. Nowadays, | |
| 17256 | 2977 however, all practical systems have a C89 compiler and GNU C supports |
| 2978 almost all of C99 and some of C11. Similarly, most systems implement | |
| 2979 POSIX.1-2001 libraries and tools, and many have POSIX.1-2008. | |
| 14502 | 2980 |
| 2981 Hence, there is little reason to support old C or non-POSIX systems, | |
| 17256 | 2982 and you may want to take advantage of standard C and POSIX to write |
| 14502 | 2983 clearer, more portable, or faster code. You should use standard |
| 2984 interfaces where possible; but if GNU extensions make your program | |
| 2985 more maintainable, powerful, or otherwise better, don't hesitate to | |
| 2986 use them. In any case, don't make your own declaration of system | |
| 2987 functions; that's a recipe for conflict. | |
| 2988 | |
| 2989 Despite the standards, nearly every library function has some sort of | |
| 2990 portability issue on some system or another. Here are some examples: | |
| 2991 | |
| 2992 @table @code | |
| 2993 @item open | |
| 2994 Names with trailing @code{/}'s are mishandled on many platforms. | |
| 2995 | |
| 2996 @item printf | |
| 2997 @code{long double} may be unimplemented; floating values Infinity and | |
| 2998 NaN are often mishandled; output for large precisions may be | |
| 2999 incorrect. | |
| 3000 | |
| 3001 @item readlink | |
| 3002 May return @code{int} instead of @code{ssize_t}. | |
| 3003 | |
| 3004 @item scanf | |
| 3005 On Windows, @code{errno} is not set on failure. | |
| 3006 @end table | |
| 3007 | |
| 3008 @cindex Gnulib | |
| 3009 @uref{http://www.gnu.org/software/gnulib/, Gnulib} is a big help in | |
| 3010 this regard. Gnulib provides implementations of standard interfaces | |
| 3011 on many of the systems that lack them, including portable | |
| 3012 implementations of enhanced GNU interfaces, thereby making their use | |
| 3013 portable, and of POSIX-1.2008 interfaces, some of which are missing | |
| 3014 even on up-to-date GNU systems. | |
| 3015 | |
| 3016 @findex xmalloc, in Gnulib | |
| 3017 @findex error messages, in Gnulib | |
| 3018 @findex data structures, in Gnulib | |
| 3019 Gnulib also provides many useful non-standard interfaces; for example, | |
| 3020 C implementations of standard data structures (hash tables, binary | |
| 3021 trees), error-checking type-safe wrappers for memory allocation | |
| 3022 functions (@code{xmalloc}, @code{xrealloc}), and output of error | |
| 3023 messages. | |
| 3024 | |
| 3025 Gnulib integrates with GNU Autoconf and Automake to remove much of the | |
| 3026 burden of writing portable code from the programmer: Gnulib makes your | |
| 3027 configure script automatically determine what features are missing and | |
| 3028 use the Gnulib code to supply the missing pieces. | |
| 3029 | |
| 3030 The Gnulib and Autoconf manuals have extensive sections on | |
| 3031 portability: @ref{Top,, Introduction, gnulib, Gnulib} and | |
| 3032 @pxref{Portable C and C++,,, autoconf, Autoconf}. Please consult them | |
| 3033 for many more details. | |
| 3034 | |
| 4958 | 3035 |
| 3036 @node Internationalization | |
| 3037 @section Internationalization | |
| 3038 @cindex internationalization | |
| 3039 | |
| 3040 @pindex gettext | |
| 3041 GNU has a library called GNU gettext that makes it easy to translate the | |
| 3042 messages in a program into various languages. You should use this | |
| 3043 library in every program. Use English for the messages as they appear | |
| 3044 in the program, and let gettext provide the way to translate them into | |
| 3045 other languages. | |
| 3046 | |
| 3047 Using GNU gettext involves putting a call to the @code{gettext} macro | |
| 3048 around each string that might need translation---like this: | |
| 3049 | |
| 3050 @example | |
| 16202 | 3051 printf (gettext ("Processing file '%s'..."), file); |
| 4958 | 3052 @end example |
| 3053 | |
| 3054 @noindent | |
| 3055 This permits GNU gettext to replace the string @code{"Processing file | |
| 16202 | 3056 '%s'..."} with a translated version. |
| 4958 | 3057 |
| 3058 Once a program uses gettext, please make a point of writing calls to | |
| 3059 @code{gettext} when you add new strings that call for translation. | |
| 3060 | |
| 3061 Using GNU gettext in a package involves specifying a @dfn{text domain | |
| 3062 name} for the package. The text domain name is used to separate the | |
| 3063 translations for this package from the translations for other packages. | |
| 3064 Normally, the text domain name should be the same as the name of the | |
| 6801 | 3065 package---for example, @samp{coreutils} for the GNU core utilities. |
| 4958 | 3066 |
| 3067 @cindex message text, and internationalization | |
| 3068 To enable gettext to work well, avoid writing code that makes | |
| 3069 assumptions about the structure of words or sentences. When you want | |
| 3070 the precise text of a sentence to vary depending on the data, use two or | |
| 3071 more alternative string constants each containing a complete sentences, | |
| 3072 rather than inserting conditionalized words or phrases into a single | |
| 3073 sentence framework. | |
| 3074 | |
| 3075 Here is an example of what not to do: | |
| 3076 | |
| 7159 | 3077 @smallexample |
| 6801 | 3078 printf ("%s is full", capacity > 5000000 ? "disk" : "floppy disk"); |
| 7159 | 3079 @end smallexample |
| 4958 | 3080 |
| 6801 | 3081 If you apply gettext to all strings, like this, |
| 4958 | 3082 |
| 7159 | 3083 @smallexample |
| 6801 | 3084 printf (gettext ("%s is full"), |
| 3085 capacity > 5000000 ? gettext ("disk") : gettext ("floppy disk")); | |
| 7159 | 3086 @end smallexample |
| 4958 | 3087 |
| 3088 @noindent | |
| 6801 | 3089 the translator will hardly know that "disk" and "floppy disk" are meant to |
| 3090 be substituted in the other string. Worse, in some languages (like French) | |
| 3091 the construction will not work: the translation of the word "full" depends | |
| 3092 on the gender of the first part of the sentence; it happens to be not the | |
| 3093 same for "disk" as for "floppy disk". | |
| 3094 | |
| 3095 Complete sentences can be translated without problems: | |
| 4958 | 3096 |
| 3097 @example | |
| 6801 | 3098 printf (capacity > 5000000 ? gettext ("disk is full") |
| 3099 : gettext ("floppy disk is full")); | |
| 4958 | 3100 @end example |
| 3101 | |
| 3102 A similar problem appears at the level of sentence structure with this | |
| 3103 code: | |
| 3104 | |
| 3105 @example | |
| 3106 printf ("# Implicit rule search has%s been done.\n", | |
| 3107 f->tried_implicit ? "" : " not"); | |
| 3108 @end example | |
| 3109 | |
| 3110 @noindent | |
| 3111 Adding @code{gettext} calls to this code cannot give correct results for | |
| 3112 all languages, because negation in some languages requires adding words | |
| 3113 at more than one place in the sentence. By contrast, adding | |
| 6946 | 3114 @code{gettext} calls does the job straightforwardly if the code starts |
| 4958 | 3115 out like this: |
| 3116 | |
| 3117 @example | |
| 3118 printf (f->tried_implicit | |
| 3119 ? "# Implicit rule search has been done.\n", | |
| 3120 : "# Implicit rule search has not been done.\n"); | |
| 3121 @end example | |
| 3122 | |
| 6801 | 3123 Another example is this one: |
| 3124 | |
| 3125 @example | |
| 3126 printf ("%d file%s processed", nfiles, | |
| 3127 nfiles != 1 ? "s" : ""); | |
| 3128 @end example | |
| 3129 | |
| 3130 @noindent | |
| 3131 The problem with this example is that it assumes that plurals are made | |
| 3132 by adding `s'. If you apply gettext to the format string, like this, | |
| 3133 | |
| 3134 @example | |
| 3135 printf (gettext ("%d file%s processed"), nfiles, | |
| 3136 nfiles != 1 ? "s" : ""); | |
| 3137 @end example | |
| 3138 | |
| 3139 @noindent | |
| 3140 the message can use different words, but it will still be forced to use | |
| 3141 `s' for the plural. Here is a better way, with gettext being applied to | |
| 3142 the two strings independently: | |
| 3143 | |
| 3144 @example | |
| 3145 printf ((nfiles != 1 ? gettext ("%d files processed") | |
| 3146 : gettext ("%d file processed")), | |
| 3147 nfiles); | |
| 3148 @end example | |
| 3149 | |
| 3150 @noindent | |
| 3151 But this still doesn't work for languages like Polish, which has three | |
| 3152 plural forms: one for nfiles == 1, one for nfiles == 2, 3, 4, 22, 23, 24, ... | |
| 3153 and one for the rest. The GNU @code{ngettext} function solves this problem: | |
| 3154 | |
| 3155 @example | |
| 3156 printf (ngettext ("%d files processed", "%d file processed", nfiles), | |
| 3157 nfiles); | |
| 3158 @end example | |
| 3159 | |
| 6066 | 3160 |
| 3161 @node Character Set | |
| 3162 @section Character Set | |
| 3163 @cindex character set | |
| 3164 @cindex encodings | |
| 3165 @cindex ASCII characters | |
| 3166 @cindex non-ASCII characters | |
| 3167 | |
| 3168 Sticking to the ASCII character set (plain text, 7-bit characters) is | |
| 3169 preferred in GNU source code comments, text documents, and other | |
| 3170 contexts, unless there is good reason to do something else because of | |
| 3171 the application domain. For example, if source code deals with the | |
| 3172 French Revolutionary calendar, it is OK if its literal strings contain | |
| 3173 accented characters in month names like ``Flor@'eal''. Also, it is OK | |
| 16158 | 3174 (but not required) to use non-ASCII characters to represent proper |
| 3175 names of contributors in change logs (@pxref{Change Logs}). | |
| 6066 | 3176 |
| 16159 | 3177 If you need to use non-ASCII characters, you should normally stick |
| 3178 with one encoding, certainly within a single file. UTF-8 is likely to | |
| 3179 be the best choice. | |
| 6066 | 3180 |
| 3181 | |
| 3182 @node Quote Characters | |
| 3183 @section Quote Characters | |
| 3184 @cindex quote characters | |
| 3185 @cindex locale-specific quote characters | |
| 3186 @cindex left quote | |
| 16202 | 3187 @cindex right quote |
| 3188 @cindex opening quote | |
| 3189 @cindex single quote | |
| 3190 @cindex double quote | |
| 6066 | 3191 @cindex grave accent |
| 16202 | 3192 @set txicodequoteundirected |
| 3193 @set txicodequotebacktick | |
| 3194 | |
| 3195 In the C locale, the output of GNU programs should stick to plain | |
| 3196 ASCII for quotation characters in messages to users: preferably 0x22 | |
| 3197 (@samp{"}) or 0x27 (@samp{'}) for both opening and closing quotes. | |
| 3198 Although GNU programs traditionally used 0x60 (@samp{`}) for opening | |
| 3199 and 0x27 (@samp{'}) for closing quotes, nowadays quotes @samp{`like | |
| 3200 this'} are typically rendered asymmetrically, so quoting @samp{"like | |
| 3201 this"} or @samp{'like this'} typically looks better. | |
| 3202 | |
| 3203 It is ok, but not required, for GNU programs to generate | |
| 3204 locale-specific quotes in non-C locales. For example: | |
| 3205 | |
| 3206 @example | |
| 3207 printf (gettext ("Processing file '%s'..."), file); | |
| 3208 @end example | |
| 3209 | |
| 3210 @noindent | |
| 3211 Here, a French translation might cause @code{gettext} to return the | |
| 3212 string @code{"Traitement de fichier | |
| 3213 @guilsinglleft{}@tie{}%s@tie{}@guilsinglright{}..."}, yielding quotes | |
| 3214 more appropriate for a French locale. | |
| 3215 | |
| 3216 Sometimes a program may need to use opening and closing quotes | |
| 3217 directly. By convention, @code{gettext} translates the string | |
| 3218 @samp{"`"} to the opening quote and the string @samp{"'"} to the | |
| 3219 closing quote, and a program can use these translations. Generally, | |
| 3220 though, it is better to translate quote characters in the context of | |
| 3221 longer strings. | |
| 3222 | |
| 3223 If the output of your program is ever likely to be parsed by another | |
| 3224 program, it is good to provide an option that makes this parsing | |
| 3225 reliable. For example, you could escape special characters using | |
| 3226 conventions from the C language or the Bourne shell. See for example | |
| 3227 the option @option{--quoting-style} of GNU @code{ls}. | |
| 3228 | |
| 3229 @clear txicodequoteundirected | |
| 3230 @clear txicodequotebacktick | |
| 6066 | 3231 |
| 3232 | |
| 4958 | 3233 @node Mmap |
| 3234 @section Mmap | |
| 3235 @findex mmap | |
| 3236 | |
| 3237 Don't assume that @code{mmap} either works on all files or fails | |
| 3238 for all files. It may work on some files and fail on others. | |
| 3239 | |
| 3240 The proper way to use @code{mmap} is to try it on the specific file for | |
| 3241 which you want to use it---and if @code{mmap} doesn't work, fall back on | |
| 3242 doing the job in another way using @code{read} and @code{write}. | |
| 3243 | |
| 3244 The reason this precaution is needed is that the GNU kernel (the HURD) | |
| 3245 provides a user-extensible file system, in which there can be many | |
| 15793 | 3246 different kinds of ``ordinary files''. Many of them support |
| 4958 | 3247 @code{mmap}, but some do not. It is important to make programs handle |
| 3248 all these kinds of files. | |
| 3249 | |
| 15793 | 3250 |
| 4958 | 3251 @node Documentation |
| 3252 @chapter Documenting Programs | |
| 3253 @cindex documentation | |
| 3254 | |
| 3255 A GNU program should ideally come with full free documentation, adequate | |
| 3256 for both reference and tutorial purposes. If the package can be | |
| 3257 programmed or extended, the documentation should cover programming or | |
| 3258 extending it, as well as just using it. | |
| 3259 | |
| 3260 @menu | |
| 3261 * GNU Manuals:: Writing proper manuals. | |
| 3262 * Doc Strings and Manuals:: Compiling doc strings doesn't make a manual. | |
| 3263 * Manual Structure Details:: Specific structure conventions. | |
| 3264 * License for Manuals:: Writing the distribution terms for a manual. | |
| 3265 * Manual Credits:: Giving credit to documentation contributors. | |
| 3266 * Printed Manuals:: Mentioning the printed manual. | |
| 3267 * NEWS File:: NEWS files supplement manuals. | |
| 9115 | 3268 * Change Logs:: Recording changes. |
| 4958 | 3269 * Man Pages:: Man pages are secondary. |
| 3270 * Reading other Manuals:: How far you can go in learning | |
| 3271 from other manuals. | |
| 3272 @end menu | |
| 3273 | |
| 3274 @node GNU Manuals | |
| 3275 @section GNU Manuals | |
| 3276 | |
| 3277 The preferred document format for the GNU system is the Texinfo | |
| 3278 formatting language. Every GNU package should (ideally) have | |
| 3279 documentation in Texinfo both for reference and for learners. Texinfo | |
| 3280 makes it possible to produce a good quality formatted book, using | |
| 3281 @TeX{}, and to generate an Info file. It is also possible to generate | |
| 3282 HTML output from Texinfo source. See the Texinfo manual, either the | |
| 3283 hardcopy, or the on-line version available through @code{info} or the | |
| 3284 Emacs Info subsystem (@kbd{C-h i}). | |
| 3285 | |
| 3286 Nowadays some other formats such as Docbook and Sgmltexi can be | |
| 3287 converted automatically into Texinfo. It is ok to produce the Texinfo | |
| 3288 documentation by conversion this way, as long as it gives good results. | |
| 3289 | |
| 6775 | 3290 Make sure your manual is clear to a reader who knows nothing about the |
| 3291 topic and reads it straight through. This means covering basic topics | |
| 3292 at the beginning, and advanced topics only later. This also means | |
| 3293 defining every specialized term when it is first used. | |
| 3294 | |
| 3295 Programmers tend to carry over the structure of the program as the | |
| 3296 structure for its documentation. But this structure is not | |
| 3297 necessarily good for explaining how to use the program; it may be | |
| 3298 irrelevant and confusing for a user. | |
| 3299 | |
| 3300 Instead, the right way to structure documentation is according to the | |
| 3301 concepts and questions that a user will have in mind when reading it. | |
| 3302 This principle applies at every level, from the lowest (ordering | |
| 3303 sentences in a paragraph) to the highest (ordering of chapter topics | |
| 3304 within the manual). Sometimes this structure of ideas matches the | |
| 4958 | 3305 structure of the implementation of the software being documented---but |
| 6775 | 3306 often they are different. An important part of learning to write good |
| 3307 documentation is to learn to notice when you have unthinkingly | |
| 3308 structured the documentation like the implementation, stop yourself, | |
| 3309 and look for better alternatives. | |
| 4958 | 3310 |
| 3311 For example, each program in the GNU system probably ought to be | |
| 3312 documented in one manual; but this does not mean each program should | |
| 3313 have its own manual. That would be following the structure of the | |
| 3314 implementation, rather than the structure that helps the user | |
| 3315 understand. | |
| 3316 | |
| 3317 Instead, each manual should cover a coherent @emph{topic}. For example, | |
| 3318 instead of a manual for @code{diff} and a manual for @code{diff3}, we | |
| 3319 have one manual for ``comparison of files'' which covers both of those | |
| 3320 programs, as well as @code{cmp}. By documenting these programs | |
| 3321 together, we can make the whole subject clearer. | |
| 3322 | |
| 3323 The manual which discusses a program should certainly document all of | |
| 3324 the program's command-line options and all of its commands. It should | |
| 3325 give examples of their use. But don't organize the manual as a list | |
| 3326 of features. Instead, organize it logically, by subtopics. Address | |
| 3327 the questions that a user will ask when thinking about the job that | |
| 3328 the program does. Don't just tell the reader what each feature can | |
| 3329 do---say what jobs it is good for, and show how to use it for those | |
| 3330 jobs. Explain what is recommended usage, and what kinds of usage | |
| 3331 users should avoid. | |
| 3332 | |
| 3333 In general, a GNU manual should serve both as tutorial and reference. | |
| 3334 It should be set up for convenient access to each topic through Info, | |
| 3335 and for reading straight through (appendixes aside). A GNU manual | |
| 3336 should give a good introduction to a beginner reading through from the | |
| 3337 start, and should also provide all the details that hackers want. | |
| 3338 The Bison manual is a good example of this---please take a look at it | |
| 3339 to see what we mean. | |
| 3340 | |
| 3341 That is not as hard as it first sounds. Arrange each chapter as a | |
| 3342 logical breakdown of its topic, but order the sections, and write their | |
| 3343 text, so that reading the chapter straight through makes sense. Do | |
| 3344 likewise when structuring the book into chapters, and when structuring a | |
| 3345 section into paragraphs. The watchword is, @emph{at each point, address | |
| 3346 the most fundamental and important issue raised by the preceding text.} | |
| 3347 | |
| 3348 If necessary, add extra chapters at the beginning of the manual which | |
| 3349 are purely tutorial and cover the basics of the subject. These provide | |
| 3350 the framework for a beginner to understand the rest of the manual. The | |
| 3351 Bison manual provides a good example of how to do this. | |
| 3352 | |
| 17362 | 3353 To serve as a reference, a manual should have an Index that lists all |
| 3354 the functions, variables, options, and important concepts that are | |
| 3355 part of the program. One combined Index should do for a short manual, | |
| 3356 but sometimes for a complex package it is better to use multiple | |
| 3357 indices. The Texinfo manual includes advice on preparing good index | |
| 3358 entries, see @ref{Index Entries, , Making Index Entries, texinfo, GNU | |
| 3359 Texinfo}, and see @ref{Indexing Commands, , Defining the Entries of an | |
| 5909 | 3360 Index, texinfo, GNU Texinfo}. |
| 4958 | 3361 |
| 3362 Don't use Unix man pages as a model for how to write GNU documentation; | |
| 3363 most of them are terse, badly structured, and give inadequate | |
| 3364 explanation of the underlying concepts. (There are, of course, some | |
| 3365 exceptions.) Also, Unix man pages use a particular format which is | |
| 3366 different from what we use in GNU manuals. | |
| 3367 | |
| 3368 Please include an email address in the manual for where to report | |
| 3369 bugs @emph{in the text of the manual}. | |
| 3370 | |
| 3371 Please do not use the term ``pathname'' that is used in Unix | |
| 3372 documentation; use ``file name'' (two words) instead. We use the term | |
| 3373 ``path'' only for search paths, which are lists of directory names. | |
| 3374 | |
| 3375 Please do not use the term ``illegal'' to refer to erroneous input to | |
| 3376 a computer program. Please use ``invalid'' for this, and reserve the | |
| 3377 term ``illegal'' for activities prohibited by law. | |
| 3378 | |
| 6775 | 3379 Please do not write @samp{()} after a function name just to indicate |
| 3380 it is a function. @code{foo ()} is not a function, it is a function | |
| 3381 call with no arguments. | |
| 3382 | |
| 4958 | 3383 @node Doc Strings and Manuals |
| 3384 @section Doc Strings and Manuals | |
| 3385 | |
| 3386 Some programming systems, such as Emacs, provide a documentation string | |
| 3387 for each function, command or variable. You may be tempted to write a | |
| 3388 reference manual by compiling the documentation strings and writing a | |
| 3389 little additional text to go around them---but you must not do it. That | |
| 3390 approach is a fundamental mistake. The text of well-written | |
| 3391 documentation strings will be entirely wrong for a manual. | |
| 3392 | |
| 3393 A documentation string needs to stand alone---when it appears on the | |
| 3394 screen, there will be no other text to introduce or explain it. | |
| 3395 Meanwhile, it can be rather informal in style. | |
| 3396 | |
| 3397 The text describing a function or variable in a manual must not stand | |
| 3398 alone; it appears in the context of a section or subsection. Other text | |
| 3399 at the beginning of the section should explain some of the concepts, and | |
| 3400 should often make some general points that apply to several functions or | |
| 3401 variables. The previous descriptions of functions and variables in the | |
| 3402 section will also have given information about the topic. A description | |
| 3403 written to stand alone would repeat some of that information; this | |
| 6946 | 3404 redundancy looks bad. Meanwhile, the informality that is acceptable in |
| 4958 | 3405 a documentation string is totally unacceptable in a manual. |
| 3406 | |
| 3407 The only good way to use documentation strings in writing a good manual | |
| 3408 is to use them as a source of information for writing good text. | |
| 3409 | |
| 3410 @node Manual Structure Details | |
| 3411 @section Manual Structure Details | |
| 3412 @cindex manual structure | |
| 3413 | |
| 3414 The title page of the manual should state the version of the programs or | |
| 3415 packages documented in the manual. The Top node of the manual should | |
| 3416 also contain this information. If the manual is changing more | |
| 3417 frequently than or independent of the program, also state a version | |
| 3418 number for the manual in both of these places. | |
| 3419 | |
| 3420 Each program documented in the manual should have a node named | |
| 3421 @samp{@var{program} Invocation} or @samp{Invoking @var{program}}. This | |
| 3422 node (together with its subnodes, if any) should describe the program's | |
| 3423 command line arguments and how to run it (the sort of information people | |
| 5301 | 3424 would look for in a man page). Start with an @samp{@@example} |
| 4958 | 3425 containing a template for all the options and arguments that the program |
| 3426 uses. | |
| 3427 | |
| 3428 Alternatively, put a menu item in some menu whose item name fits one of | |
| 3429 the above patterns. This identifies the node which that item points to | |
| 3430 as the node for this purpose, regardless of the node's actual name. | |
| 3431 | |
| 3432 The @samp{--usage} feature of the Info reader looks for such a node | |
| 3433 or menu item in order to find the relevant text, so it is essential | |
| 3434 for every Texinfo file to have one. | |
| 3435 | |
| 3436 If one manual describes several programs, it should have such a node for | |
| 3437 each program described in the manual. | |
| 3438 | |
| 3439 @node License for Manuals | |
| 3440 @section License for Manuals | |
| 3441 @cindex license for manuals | |
| 3442 | |
| 3443 Please use the GNU Free Documentation License for all GNU manuals that | |
| 3444 are more than a few pages long. Likewise for a collection of short | |
| 3445 documents---you only need one copy of the GNU FDL for the whole | |
| 3446 collection. For a single short document, you can use a very permissive | |
| 3447 non-copyleft license, to avoid taking up space with a long license. | |
| 3448 | |
| 3449 See @uref{http://www.gnu.org/copyleft/fdl-howto.html} for more explanation | |
| 3450 of how to employ the GFDL. | |
| 3451 | |
| 3452 Note that it is not obligatory to include a copy of the GNU GPL or GNU | |
| 3453 LGPL in a manual whose license is neither the GPL nor the LGPL. It can | |
| 3454 be a good idea to include the program's license in a large manual; in a | |
| 3455 short manual, whose size would be increased considerably by including | |
| 3456 the program's license, it is probably better not to include it. | |
| 3457 | |
| 3458 @node Manual Credits | |
| 3459 @section Manual Credits | |
| 3460 @cindex credits for manuals | |
| 3461 | |
| 3462 Please credit the principal human writers of the manual as the authors, | |
| 3463 on the title page of the manual. If a company sponsored the work, thank | |
| 3464 the company in a suitable place in the manual, but do not cite the | |
| 3465 company as an author. | |
| 3466 | |
| 3467 @node Printed Manuals | |
| 3468 @section Printed Manuals | |
| 3469 | |
| 3470 The FSF publishes some GNU manuals in printed form. To encourage sales | |
| 3471 of these manuals, the on-line versions of the manual should mention at | |
| 3472 the very start that the printed manual is available and should point at | |
| 3473 information for getting it---for instance, with a link to the page | |
| 3474 @url{http://www.gnu.org/order/order.html}. This should not be included | |
| 3475 in the printed manual, though, because there it is redundant. | |
| 3476 | |
| 3477 It is also useful to explain in the on-line forms of the manual how the | |
| 3478 user can print out the manual from the sources. | |
| 3479 | |
| 3480 @node NEWS File | |
| 3481 @section The NEWS File | |
| 3482 @cindex @file{NEWS} file | |
| 3483 | |
| 3484 In addition to its manual, the package should have a file named | |
| 3485 @file{NEWS} which contains a list of user-visible changes worth | |
| 3486 mentioning. In each new release, add items to the front of the file and | |
| 3487 identify the version they pertain to. Don't discard old items; leave | |
| 3488 them in the file after the newer items. This way, a user upgrading from | |
| 3489 any previous version can see what is new. | |
| 3490 | |
| 3491 If the @file{NEWS} file gets very long, move some of the older items | |
| 3492 into a file named @file{ONEWS} and put a note at the end referring the | |
| 3493 user to that file. | |
| 3494 | |
| 3495 @node Change Logs | |
| 3496 @section Change Logs | |
| 3497 @cindex change logs | |
| 3498 | |
| 3499 Keep a change log to describe all the changes made to program source | |
| 3500 files. The purpose of this is so that people investigating bugs in the | |
| 3501 future will know about the changes that might have introduced the bug. | |
| 3502 Often a new bug can be found by looking at what was recently changed. | |
| 3503 More importantly, change logs can help you eliminate conceptual | |
| 3504 inconsistencies between different parts of a program, by giving you a | |
| 3505 history of how the conflicting concepts arose and who they came from. | |
| 3506 | |
| 3507 @menu | |
| 6725 | 3508 * Change Log Concepts:: |
| 3509 * Style of Change Logs:: | |
| 3510 * Simple Changes:: | |
| 3511 * Conditional Changes:: | |
| 4958 | 3512 * Indicating the Part Changed:: |
| 3513 @end menu | |
| 3514 | |
| 3515 @node Change Log Concepts | |
| 3516 @subsection Change Log Concepts | |
| 3517 | |
| 16890 | 3518 @cindex change set |
| 3519 @cindex batch of changes | |
| 4958 | 3520 You can think of the change log as a conceptual ``undo list'' which |
| 3521 explains how earlier versions were different from the current version. | |
| 16890 | 3522 People can see the current version; they don't need the change log to |
| 3523 tell them what is in it. What they want from a change log is a clear | |
| 3524 explanation of how the earlier version differed. Each @dfn{entry} in | |
| 3525 a change log describes either an individual change or the smallest | |
| 3526 batch of changes that belong together, also known as a @dfn{change | |
| 3527 set}. | |
| 16957 | 3528 @cindex title, change log entry |
| 3529 @cindex description, change log entry | |
| 3530 For later reference or for summarizing, sometimes it is useful to | |
| 3531 start the entry with a one-line description (sometimes called a | |
| 3532 @dfn{title}) to describe its overall purpose. | |
| 3533 | |
| 3534 In the past, we recommended not mentioning changes in non-software | |
| 3535 files (manuals, help files, media files, etc.)@: in change logs. | |
| 3536 However, we've been advised that it is a good idea to include them, | |
| 3537 for the sake of copyright records. | |
| 4958 | 3538 |
| 3539 The change log file is normally called @file{ChangeLog} and covers an | |
| 3540 entire directory. Each directory can have its own change log, or a | |
| 12897 | 3541 directory can use the change log of its parent directory---it's up to |
| 4958 | 3542 you. |
| 3543 | |
| 3544 Another alternative is to record change log information with a version | |
| 3545 control system such as RCS or CVS. This can be converted automatically | |
| 3546 to a @file{ChangeLog} file using @code{rcs2log}; in Emacs, the command | |
| 3547 @kbd{C-x v a} (@code{vc-update-change-log}) does the job. | |
| 3548 | |
| 16957 | 3549 For changes to code, there's no need to describe the full purpose of |
| 3550 the changes or how they work together. If you think that a change | |
| 3551 calls for explanation, you're probably right. Please do explain | |
| 3552 it---but please put the full explanation in comments in the code, | |
| 3553 where people will see it whenever they see the code. For example, | |
| 3554 ``New function'' is enough for the change log when you add a function, | |
| 3555 because there should be a comment before the function definition to | |
| 3556 explain what it does. | |
| 3557 | |
| 3558 For changes to files that do not support a comment syntax (e.g., media | |
| 3559 files), it is ok to include the full explanation in the change log file, | |
| 3560 after the title and before the list of individual changes. | |
| 4958 | 3561 |
| 3562 The easiest way to add an entry to @file{ChangeLog} is with the Emacs | |
| 16890 | 3563 command @kbd{M-x add-change-log-entry}. An individual change should |
| 3564 have an asterisk, the name of the changed file, and then in | |
| 3565 parentheses the name of the changed functions, variables or whatever, | |
| 3566 followed by a colon. Then describe the changes you made to that | |
| 3567 function or variable. | |
| 3568 | |
| 4958 | 3569 |
| 3570 @node Style of Change Logs | |
| 3571 @subsection Style of Change Logs | |
| 3572 @cindex change logs, style | |
| 3573 | |
| 3574 Here are some simple examples of change log entries, starting with the | |
| 3575 header line that says who made the change and when it was installed, | |
| 3576 followed by descriptions of specific changes. (These examples are | |
| 3577 drawn from Emacs and GCC.) | |
| 3578 | |
| 3579 @example | |
| 3580 1998-08-17 Richard Stallman <rms@@gnu.org> | |
| 3581 | |
| 3582 * register.el (insert-register): Return nil. | |
| 3583 (jump-to-register): Likewise. | |
| 3584 | |
| 3585 * sort.el (sort-subr): Return nil. | |
| 3586 | |
| 3587 * tex-mode.el (tex-bibtex-file, tex-file, tex-region): | |
| 3588 Restart the tex shell if process is gone or stopped. | |
| 3589 (tex-shell-running): New function. | |
| 3590 | |
| 3591 * expr.c (store_one_arg): Round size up for move_block_to_reg. | |
| 3592 (expand_call): Round up when emitting USE insns. | |
| 3593 * stmt.c (assign_parms): Round size up for move_block_from_reg. | |
| 3594 @end example | |
| 3595 | |
| 3596 It's important to name the changed function or variable in full. Don't | |
| 3597 abbreviate function or variable names, and don't combine them. | |
| 3598 Subsequent maintainers will often search for a function name to find all | |
| 3599 the change log entries that pertain to it; if you abbreviate the name, | |
| 3600 they won't find it when they search. | |
| 3601 | |
| 3602 For example, some people are tempted to abbreviate groups of function | |
| 3603 names by writing @samp{* register.el (@{insert,jump-to@}-register)}; | |
| 3604 this is not a good idea, since searching for @code{jump-to-register} or | |
| 3605 @code{insert-register} would not find that entry. | |
| 3606 | |
| 16890 | 3607 Separate unrelated change log entries with blank lines. Don't put |
| 3608 blank lines between individual changes of an entry. You can omit the | |
| 3609 file name and the asterisk when successive individual changes are in | |
| 3610 the same file. | |
| 4958 | 3611 |
| 3612 Break long lists of function names by closing continued lines with | |
| 3613 @samp{)}, rather than @samp{,}, and opening the continuation with | |
| 3614 @samp{(} as in this example: | |
| 3615 | |
| 3616 @example | |
| 3617 * keyboard.c (menu_bar_items, tool_bar_items) | |
| 16202 | 3618 (Fexecute_extended_command): Deal with 'keymap' property. |
| 4958 | 3619 @end example |
| 3620 | |
| 3621 When you install someone else's changes, put the contributor's name in | |
| 3622 the change log entry rather than in the text of the entry. In other | |
| 3623 words, write this: | |
| 3624 | |
| 3625 @example | |
| 3626 2002-07-14 John Doe <jdoe@@gnu.org> | |
| 3627 | |
| 3628 * sewing.c: Make it sew. | |
| 3629 @end example | |
| 3630 | |
| 3631 @noindent | |
| 3632 rather than this: | |
| 3633 | |
| 3634 @example | |
| 3635 2002-07-14 Usual Maintainer <usual@@gnu.org> | |
| 3636 | |
| 3637 * sewing.c: Make it sew. Patch by jdoe@@gnu.org. | |
| 3638 @end example | |
| 3639 | |
| 3640 As for the date, that should be the date you applied the change. | |
| 3641 | |
| 3642 @node Simple Changes | |
| 3643 @subsection Simple Changes | |
| 3644 | |
| 3645 Certain simple kinds of changes don't need much detail in the change | |
| 3646 log. | |
| 3647 | |
| 3648 When you change the calling sequence of a function in a simple fashion, | |
| 3649 and you change all the callers of the function to use the new calling | |
| 3650 sequence, there is no need to make individual entries for all the | |
| 3651 callers that you changed. Just write in the entry for the function | |
| 3652 being called, ``All callers changed''---like this: | |
| 3653 | |
| 3654 @example | |
| 3655 * keyboard.c (Fcommand_execute): New arg SPECIAL. | |
| 3656 All callers changed. | |
| 3657 @end example | |
| 3658 | |
| 3659 When you change just comments or doc strings, it is enough to write an | |
| 3660 entry for the file, without mentioning the functions. Just ``Doc | |
| 3661 fixes'' is enough for the change log. | |
| 3662 | |
| 3663 There's no technical need to make change log entries for documentation | |
| 3664 files. This is because documentation is not susceptible to bugs that | |
| 3665 are hard to fix. Documentation does not consist of parts that must | |
| 3666 interact in a precisely engineered fashion. To correct an error, you | |
| 3667 need not know the history of the erroneous passage; it is enough to | |
| 3668 compare what the documentation says with the way the program actually | |
| 3669 works. | |
| 3670 | |
| 3671 However, you should keep change logs for documentation files when the | |
| 3672 project gets copyright assignments from its contributors, so as to | |
| 3673 make the records of authorship more accurate. | |
| 3674 | |
| 3675 @node Conditional Changes | |
| 3676 @subsection Conditional Changes | |
| 3677 @cindex conditional changes, and change logs | |
| 3678 @cindex change logs, conditional changes | |
| 3679 | |
| 16186 | 3680 Source files can often contain code that is conditional to build-time |
| 3681 or static conditions. For example, C programs can contain | |
| 3682 compile-time @code{#if} conditionals; programs implemented in | |
| 3683 interpreted languages can contain module imports of function | |
| 3684 definitions that are only performed for certain versions of the | |
| 3685 interpreter; and Automake @file{Makefile.am} files can contain | |
| 3686 variable definitions or target declarations that are only to be | |
| 3687 considered if a configure-time Automake conditional is true. | |
| 3688 | |
| 3689 Many changes are conditional as well: sometimes you add a new variable, | |
| 3690 or function, or even a new program or library, which is entirely | |
| 3691 dependent on a build-time condition. It is useful to indicate | |
| 3692 in the change log the conditions for which a change applies. | |
| 3693 | |
| 3694 Our convention for indicating conditional changes is to use | |
| 3695 @emph{square brackets around the name of the condition}. | |
| 3696 | |
| 3697 Conditional changes can happen in numerous scenarios and with many | |
| 3698 variations, so here are some examples to help clarify. This first | |
| 3699 example describes changes in C, Perl, and Python files which are | |
| 3700 conditional but do not have an associated function or entity name: | |
| 4958 | 3701 |
| 3702 @example | |
| 16186 | 3703 * xterm.c [SOLARIS2]: Include <string.h>. |
| 3704 * FilePath.pm [$^O eq 'VMS']: Import the VMS::Feature module. | |
| 3705 * framework.py [sys.version_info < (2, 6)]: Make "with" statement | |
| 3706 available by importing it from __future__, | |
| 3707 to support also python 2.5. | |
| 4958 | 3708 @end example |
| 3709 | |
| 16186 | 3710 Our other examples will for simplicity be limited to C, as the minor |
| 3711 changes necessary to adapt them to other languages should be | |
| 3712 self-evident. | |
| 3713 | |
| 3714 Next, here is an entry describing a new definition which is entirely | |
| 3715 conditional: the C macro @code{FRAME_WINDOW_P} is defined (and used) | |
| 3716 only when the macro @code{HAVE_X_WINDOWS} is defined: | |
| 4958 | 3717 |
| 3718 @example | |
| 3719 * frame.h [HAVE_X_WINDOWS] (FRAME_WINDOW_P): Macro defined. | |
| 3720 @end example | |
| 3721 | |
| 16186 | 3722 Next, an entry for a change within the function @code{init_display}, |
| 3723 whose definition as a whole is unconditional, but the changes | |
| 3724 themselves are contained in a @samp{#ifdef HAVE_LIBNCURSES} | |
| 3725 conditional: | |
| 4958 | 3726 |
| 3727 @example | |
| 3728 * dispnew.c (init_display) [HAVE_LIBNCURSES]: If X, call tgetent. | |
| 3729 @end example | |
| 3730 | |
| 16186 | 3731 Finally, here is an entry for a change that takes effect only when |
| 4958 | 3732 a certain macro is @emph{not} defined: |
| 3733 | |
| 3734 @example | |
| 16890 | 3735 * host.c (gethostname) [!HAVE_SOCKETS]: Replace with winsock version. |
| 4958 | 3736 @end example |
| 3737 | |
| 16890 | 3738 |
| 4958 | 3739 @node Indicating the Part Changed |
| 3740 @subsection Indicating the Part Changed | |
| 3741 | |
| 3742 Indicate the part of a function which changed by using angle brackets | |
| 3743 enclosing an indication of what the changed part does. Here is an entry | |
| 3744 for a change in the part of the function @code{sh-while-getopts} that | |
| 3745 deals with @code{sh} commands: | |
| 3746 | |
| 3747 @example | |
| 3748 * progmodes/sh-script.el (sh-while-getopts) <sh>: Handle case that | |
| 3749 user-specified option string is empty. | |
| 3750 @end example | |
| 3751 | |
| 3752 | |
| 3753 @node Man Pages | |
| 3754 @section Man Pages | |
| 3755 @cindex man pages | |
| 3756 | |
| 3757 In the GNU project, man pages are secondary. It is not necessary or | |
| 3758 expected for every GNU program to have a man page, but some of them do. | |
| 3759 It's your choice whether to include a man page in your program. | |
| 3760 | |
| 3761 When you make this decision, consider that supporting a man page | |
| 3762 requires continual effort each time the program is changed. The time | |
| 3763 you spend on the man page is time taken away from more useful work. | |
| 3764 | |
| 3765 For a simple program which changes little, updating the man page may be | |
| 3766 a small job. Then there is little reason not to include a man page, if | |
| 3767 you have one. | |
| 3768 | |
| 3769 For a large program that changes a great deal, updating a man page may | |
| 3770 be a substantial burden. If a user offers to donate a man page, you may | |
| 3771 find this gift costly to accept. It may be better to refuse the man | |
| 3772 page unless the same person agrees to take full responsibility for | |
| 3773 maintaining it---so that you can wash your hands of it entirely. If | |
| 3774 this volunteer later ceases to do the job, then don't feel obliged to | |
| 3775 pick it up yourself; it may be better to withdraw the man page from the | |
| 3776 distribution until someone else agrees to update it. | |
| 3777 | |
| 3778 When a program changes only a little, you may feel that the | |
| 3779 discrepancies are small enough that the man page remains useful without | |
| 3780 updating. If so, put a prominent note near the beginning of the man | |
| 3781 page explaining that you don't maintain it and that the Texinfo manual | |
| 3782 is more authoritative. The note should say how to access the Texinfo | |
| 3783 documentation. | |
| 3784 | |
| 11617 | 3785 Be sure that man pages include a copyright statement and free license. |
| 3786 The simple all-permissive license is appropriate for simple man pages | |
| 3787 (@pxref{License Notices for Other Files,,,maintain,Information for GNU | |
| 3788 Maintainers}). | |
|
5495
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3789 |
|
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3790 For long man pages, with enough explanation and documentation that |
|
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3791 they can be considered true manuals, use the GFDL (@pxref{License for |
|
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|
3792 Manuals}). |
|
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3793 |
| 5301 | 3794 Finally, the GNU help2man program |
| 3795 (@uref{http://www.gnu.org/software/help2man/}) is one way to automate | |
| 3796 generation of a man page, in this case from @option{--help} output. | |
| 3797 This is sufficient in many cases. | |
| 3798 | |
| 4958 | 3799 @node Reading other Manuals |
| 3800 @section Reading other Manuals | |
| 3801 | |
| 3802 There may be non-free books or documentation files that describe the | |
| 3803 program you are documenting. | |
| 3804 | |
| 3805 It is ok to use these documents for reference, just as the author of a | |
| 3806 new algebra textbook can read other books on algebra. A large portion | |
| 3807 of any non-fiction book consists of facts, in this case facts about how | |
| 3808 a certain program works, and these facts are necessarily the same for | |
| 3809 everyone who writes about the subject. But be careful not to copy your | |
| 3810 outline structure, wording, tables or examples from preexisting non-free | |
| 3811 documentation. Copying from free documentation may be ok; please check | |
| 3812 with the FSF about the individual case. | |
| 3813 | |
| 3814 @node Managing Releases | |
| 3815 @chapter The Release Process | |
| 3816 @cindex releasing | |
| 3817 | |
| 3818 Making a release is more than just bundling up your source files in a | |
| 3819 tar file and putting it up for FTP. You should set up your software so | |
| 3820 that it can be configured to run on a variety of systems. Your Makefile | |
| 3821 should conform to the GNU standards described below, and your directory | |
| 3822 layout should also conform to the standards discussed below. Doing so | |
| 3823 makes it easy to include your package into the larger framework of | |
| 3824 all GNU software. | |
| 3825 | |
| 3826 @menu | |
| 9115 | 3827 * Configuration:: How configuration of GNU packages should work. |
| 3828 * Makefile Conventions:: Makefile conventions. | |
| 3829 * Releases:: Making releases | |
| 4958 | 3830 @end menu |
| 3831 | |
| 3832 @node Configuration | |
| 3833 @section How Configuration Should Work | |
| 3834 @cindex program configuration | |
| 3835 | |
| 3836 @pindex configure | |
| 3837 Each GNU distribution should come with a shell script named | |
| 3838 @code{configure}. This script is given arguments which describe the | |
| 3839 kind of machine and system you want to compile the program for. | |
| 3840 The @code{configure} script must record the configuration options so | |
| 3841 that they affect compilation. | |
| 3842 | |
| 10290 | 3843 The description here is the specification of the interface for the |
| 3844 @code{configure} script in GNU packages. Many packages implement it | |
| 3845 using GNU Autoconf (@pxref{Top,, Introduction, autoconf, Autoconf}) | |
| 3846 and/or GNU Automake (@pxref{Top,, Introduction, automake, Automake}), | |
| 3847 but you do not have to use these tools. You can implement it any way | |
| 3848 you like; for instance, by making @code{configure} be a wrapper around | |
| 3849 a completely different configuration system. | |
| 3850 | |
| 3851 Another way for the @code{configure} script to operate is to make a | |
| 3852 link from a standard name such as @file{config.h} to the proper | |
| 3853 configuration file for the chosen system. If you use this technique, | |
| 3854 the distribution should @emph{not} contain a file named | |
| 3855 @file{config.h}. This is so that people won't be able to build the | |
| 3856 program without configuring it first. | |
| 4958 | 3857 |
| 3858 Another thing that @code{configure} can do is to edit the Makefile. If | |
| 3859 you do this, the distribution should @emph{not} contain a file named | |
| 3860 @file{Makefile}. Instead, it should include a file @file{Makefile.in} which | |
| 3861 contains the input used for editing. Once again, this is so that people | |
| 3862 won't be able to build the program without configuring it first. | |
| 3863 | |
| 3864 If @code{configure} does write the @file{Makefile}, then @file{Makefile} | |
| 3865 should have a target named @file{Makefile} which causes @code{configure} | |
| 3866 to be rerun, setting up the same configuration that was set up last | |
| 3867 time. The files that @code{configure} reads should be listed as | |
| 3868 dependencies of @file{Makefile}. | |
| 3869 | |
| 3870 All the files which are output from the @code{configure} script should | |
| 3871 have comments at the beginning explaining that they were generated | |
| 3872 automatically using @code{configure}. This is so that users won't think | |
| 3873 of trying to edit them by hand. | |
| 3874 | |
| 3875 The @code{configure} script should write a file named @file{config.status} | |
| 3876 which describes which configuration options were specified when the | |
| 3877 program was last configured. This file should be a shell script which, | |
| 3878 if run, will recreate the same configuration. | |
| 3879 | |
| 3880 The @code{configure} script should accept an option of the form | |
| 3881 @samp{--srcdir=@var{dirname}} to specify the directory where sources are found | |
| 3882 (if it is not the current directory). This makes it possible to build | |
| 3883 the program in a separate directory, so that the actual source directory | |
| 3884 is not modified. | |
| 3885 | |
| 3886 If the user does not specify @samp{--srcdir}, then @code{configure} should | |
| 3887 check both @file{.} and @file{..} to see if it can find the sources. If | |
| 3888 it finds the sources in one of these places, it should use them from | |
| 3889 there. Otherwise, it should report that it cannot find the sources, and | |
| 3890 should exit with nonzero status. | |
| 3891 | |
| 3892 Usually the easy way to support @samp{--srcdir} is by editing a | |
| 3893 definition of @code{VPATH} into the Makefile. Some rules may need to | |
| 3894 refer explicitly to the specified source directory. To make this | |
| 3895 possible, @code{configure} can add to the Makefile a variable named | |
| 3896 @code{srcdir} whose value is precisely the specified directory. | |
| 3897 | |
| 9740 | 3898 In addition, the @samp{configure} script should take options |
| 3899 corresponding to most of the standard directory variables | |
| 3900 (@pxref{Directory Variables}). Here is the list: | |
| 3901 | |
| 3902 @example | |
| 3903 --prefix --exec-prefix --bindir --sbindir --libexecdir --sysconfdir | |
| 3904 --sharedstatedir --localstatedir --libdir --includedir --oldincludedir | |
| 3905 --datarootdir --datadir --infodir --localedir --mandir --docdir | |
| 3906 --htmldir --dvidir --pdfdir --psdir | |
| 3907 @end example | |
| 3908 | |
| 4958 | 3909 The @code{configure} script should also take an argument which specifies the |
| 3910 type of system to build the program for. This argument should look like | |
| 3911 this: | |
| 3912 | |
| 3913 @example | |
| 3914 @var{cpu}-@var{company}-@var{system} | |
| 3915 @end example | |
| 3916 | |
| 3917 For example, an Athlon-based GNU/Linux system might be | |
| 3918 @samp{i686-pc-linux-gnu}. | |
| 3919 | |
| 3920 The @code{configure} script needs to be able to decode all plausible | |
| 3921 alternatives for how to describe a machine. Thus, | |
| 6066 | 3922 @samp{athlon-pc-gnu/linux} would be a valid alias. There is a shell |
| 3923 script called | |
| 9823 | 3924 @uref{http://git.savannah.gnu.org/@/gitweb/@/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD, |
| 6066 | 3925 @file{config.sub}} that you can use as a subroutine to validate system |
| 3926 types and canonicalize aliases. | |
| 4958 | 3927 |
| 3928 The @code{configure} script should also take the option | |
| 3929 @option{--build=@var{buildtype}}, which should be equivalent to a | |
| 3930 plain @var{buildtype} argument. For example, @samp{configure | |
| 3931 --build=i686-pc-linux-gnu} is equivalent to @samp{configure | |
| 3932 i686-pc-linux-gnu}. When the build type is not specified by an option | |
| 6066 | 3933 or argument, the @code{configure} script should normally guess it using |
| 3934 the shell script | |
| 9823 | 3935 @uref{http://git.savannah.gnu.org/@/gitweb/@/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD, |
| 6066 | 3936 @file{config.guess}}. |
| 4958 | 3937 |
| 3938 @cindex optional features, configure-time | |
| 3939 Other options are permitted to specify in more detail the software | |
| 7159 | 3940 or hardware present on the machine, to include or exclude optional parts |
| 3941 of the package, or to adjust the name of some tools or arguments to them: | |
| 4958 | 3942 |
| 3943 @table @samp | |
| 3944 @item --enable-@var{feature}@r{[}=@var{parameter}@r{]} | |
| 3945 Configure the package to build and install an optional user-level | |
| 3946 facility called @var{feature}. This allows users to choose which | |
| 3947 optional features to include. Giving an optional @var{parameter} of | |
| 3948 @samp{no} should omit @var{feature}, if it is built by default. | |
| 3949 | |
| 3950 No @samp{--enable} option should @strong{ever} cause one feature to | |
| 3951 replace another. No @samp{--enable} option should ever substitute one | |
| 3952 useful behavior for another useful behavior. The only proper use for | |
| 3953 @samp{--enable} is for questions of whether to build part of the program | |
| 3954 or exclude it. | |
| 3955 | |
| 3956 @item --with-@var{package} | |
| 3957 @c @r{[}=@var{parameter}@r{]} | |
| 3958 The package @var{package} will be installed, so configure this package | |
| 3959 to work with @var{package}. | |
| 3960 | |
| 3961 @c Giving an optional @var{parameter} of | |
| 3962 @c @samp{no} should omit @var{package}, if it is used by default. | |
| 3963 | |
| 3964 Possible values of @var{package} include | |
| 3965 @samp{gnu-as} (or @samp{gas}), @samp{gnu-ld}, @samp{gnu-libc}, | |
| 3966 @samp{gdb}, | |
| 3967 @samp{x}, | |
| 3968 and | |
| 3969 @samp{x-toolkit}. | |
| 3970 | |
| 3971 Do not use a @samp{--with} option to specify the file name to use to | |
| 3972 find certain files. That is outside the scope of what @samp{--with} | |
| 3973 options are for. | |
| 7159 | 3974 |
| 3975 @item @var{variable}=@var{value} | |
| 3976 Set the value of the variable @var{variable} to @var{value}. This is | |
| 3977 used to override the default values of commands or arguments in the | |
| 3978 build process. For example, the user could issue @samp{configure | |
| 3979 CFLAGS=-g CXXFLAGS=-g} to build with debugging information and without | |
| 3980 the default optimization. | |
| 3981 | |
| 3982 Specifying variables as arguments to @code{configure}, like this: | |
| 3983 @example | |
| 3984 ./configure CC=gcc | |
| 3985 @end example | |
| 3986 is preferable to setting them in environment variables: | |
| 3987 @example | |
| 3988 CC=gcc ./configure | |
| 3989 @end example | |
| 3990 as it helps to recreate the same configuration later with | |
| 11990 | 3991 @file{config.status}. However, both methods should be supported. |
| 4958 | 3992 @end table |
| 3993 | |
| 7159 | 3994 All @code{configure} scripts should accept all of the ``detail'' |
| 3995 options and the variable settings, whether or not they make any | |
| 3996 difference to the particular package at hand. In particular, they | |
| 3997 should accept any option that starts with @samp{--with-} or | |
| 3998 @samp{--enable-}. This is so users will be able to configure an | |
| 3999 entire GNU source tree at once with a single set of options. | |
| 4958 | 4000 |
| 4001 You will note that the categories @samp{--with-} and @samp{--enable-} | |
| 4002 are narrow: they @strong{do not} provide a place for any sort of option | |
| 4003 you might think of. That is deliberate. We want to limit the possible | |
| 4004 configuration options in GNU software. We do not want GNU programs to | |
| 4005 have idiosyncratic configuration options. | |
| 4006 | |
| 4007 Packages that perform part of the compilation process may support | |
| 4008 cross-compilation. In such a case, the host and target machines for the | |
| 4009 program may be different. | |
| 4010 | |
| 4011 The @code{configure} script should normally treat the specified type of | |
| 4012 system as both the host and the target, thus producing a program which | |
| 4013 works for the same type of machine that it runs on. | |
| 4014 | |
| 4015 To compile a program to run on a host type that differs from the build | |
| 4016 type, use the configure option @option{--host=@var{hosttype}}, where | |
| 4017 @var{hosttype} uses the same syntax as @var{buildtype}. The host type | |
| 4018 normally defaults to the build type. | |
| 4019 | |
| 4020 To configure a cross-compiler, cross-assembler, or what have you, you | |
| 4021 should specify a target different from the host, using the configure | |
| 4022 option @samp{--target=@var{targettype}}. The syntax for | |
| 4023 @var{targettype} is the same as for the host type. So the command would | |
| 4024 look like this: | |
| 4025 | |
| 4026 @example | |
| 4027 ./configure --host=@var{hosttype} --target=@var{targettype} | |
| 4028 @end example | |
| 4029 | |
| 4030 The target type normally defaults to the host type. | |
| 4031 Programs for which cross-operation is not meaningful need not accept the | |
| 4032 @samp{--target} option, because configuring an entire operating system for | |
| 4033 cross-operation is not a meaningful operation. | |
| 4034 | |
| 4035 Some programs have ways of configuring themselves automatically. If | |
| 4036 your program is set up to do this, your @code{configure} script can simply | |
| 4037 ignore most of its arguments. | |
| 4038 | |
| 4039 @comment The makefile standards are in a separate file that is also | |
| 4040 @comment included by make.texinfo. Done by roland@gnu.ai.mit.edu on 1/6/93. | |
| 4041 @comment For this document, turn chapters into sections, etc. | |
| 4042 @lowersections | |
| 4043 @include make-stds.texi | |
| 4044 @raisesections | |
| 4045 | |
| 4046 @node Releases | |
| 4047 @section Making Releases | |
| 4048 @cindex packaging | |
| 4049 | |
| 17142 | 4050 @cindex version numbers, for releases |
| 4958 | 4051 You should identify each release with a pair of version numbers, a |
| 4052 major version and a minor. We have no objection to using more than | |
| 4053 two numbers, but it is very unlikely that you really need them. | |
| 4054 | |
| 4055 Package the distribution of @code{Foo version 69.96} up in a gzipped tar | |
| 4056 file with the name @file{foo-69.96.tar.gz}. It should unpack into a | |
| 4057 subdirectory named @file{foo-69.96}. | |
| 4058 | |
| 4059 Building and installing the program should never modify any of the files | |
| 4060 contained in the distribution. This means that all the files that form | |
| 4061 part of the program in any way must be classified into @dfn{source | |
| 4062 files} and @dfn{non-source files}. Source files are written by humans | |
| 4063 and never changed automatically; non-source files are produced from | |
| 4064 source files by programs under the control of the Makefile. | |
| 4065 | |
| 4066 @cindex @file{README} file | |
| 17142 | 4067 The distribution should contain a file named @file{README} with a |
| 4068 general overview of the package: | |
| 4069 | |
| 4070 @itemize | |
| 4071 @item the name of the package; | |
| 4072 | |
| 4073 @item the version number of the package, or refer to where in the | |
| 4074 package the version can be found; | |
| 4075 | |
| 4076 @item a general description of what the package does; | |
| 4077 | |
| 17256 | 4078 @item a reference to the file @file{INSTALL}, which |
| 17142 | 4079 should in turn contain an explanation of the installation procedure; |
| 4080 | |
| 4081 @item a brief explanation of any unusual top-level directories or | |
| 4082 files, or other hints for readers to find their way around the source; | |
| 4083 | |
| 4084 @item a reference to the file which contains the copying conditions. | |
| 4085 The GNU GPL, if used, should be in a file called @file{COPYING}. If | |
| 4086 the GNU LGPL is used, it should be in a file called | |
| 11485 | 4087 @file{COPYING.LESSER}. |
| 17142 | 4088 @end itemize |
| 4958 | 4089 |
| 15494 | 4090 Naturally, all the source files must be in the distribution. It is |
| 4091 okay to include non-source files in the distribution along with the | |
| 4092 source files they are generated from, provided they are up-to-date | |
| 4093 with the source they are made from, and machine-independent, so that | |
| 4094 normal building of the distribution will never modify them. We | |
| 4095 commonly include non-source files produced by Autoconf, Automake, | |
| 17142 | 4096 Bison, @code{flex}, @TeX{}, and @code{makeinfo}; this helps avoid |
| 4958 | 4097 unnecessary dependencies between our distributions, so that users can |
| 17142 | 4098 install whichever versions of whichever packages they like. Do not |
| 4099 induce new dependencies on other software lightly. | |
| 4958 | 4100 |
| 4101 Non-source files that might actually be modified by building and | |
| 4102 installing the program should @strong{never} be included in the | |
| 4103 distribution. So if you do distribute non-source files, always make | |
| 4104 sure they are up to date when you make a new distribution. | |
| 4105 | |
| 12439 | 4106 Make sure that all the files in the distribution are world-readable, and |
| 4107 that directories are world-readable and world-searchable (octal mode 755). | |
| 4108 We used to recommend that all directories in the distribution also be | |
| 4109 world-writable (octal mode 777), because ancient versions of @code{tar} | |
| 4110 would otherwise not cope when extracting the archive as an unprivileged | |
| 4111 user. That can easily lead to security issues when creating the archive, | |
| 4112 however, so now we recommend against that. | |
| 4958 | 4113 |
| 4114 Don't include any symbolic links in the distribution itself. If the tar | |
| 4115 file contains symbolic links, then people cannot even unpack it on | |
| 4116 systems that don't support symbolic links. Also, don't use multiple | |
| 4117 names for one file in different directories, because certain file | |
| 4118 systems cannot handle this and that prevents unpacking the | |
| 4119 distribution. | |
| 4120 | |
| 4121 Try to make sure that all the file names will be unique on MS-DOS. A | |
| 4122 name on MS-DOS consists of up to 8 characters, optionally followed by a | |
| 4123 period and up to three characters. MS-DOS will truncate extra | |
| 4124 characters both before and after the period. Thus, | |
| 4125 @file{foobarhacker.c} and @file{foobarhacker.o} are not ambiguous; they | |
| 4126 are truncated to @file{foobarha.c} and @file{foobarha.o}, which are | |
| 4127 distinct. | |
| 4128 | |
| 4129 @cindex @file{texinfo.tex}, in a distribution | |
| 4130 Include in your distribution a copy of the @file{texinfo.tex} you used | |
| 4131 to test print any @file{*.texinfo} or @file{*.texi} files. | |
| 4132 | |
| 4133 Likewise, if your program uses small GNU software packages like regex, | |
| 4134 getopt, obstack, or termcap, include them in the distribution file. | |
| 4135 Leaving them out would make the distribution file a little smaller at | |
| 4136 the expense of possible inconvenience to a user who doesn't know what | |
| 4137 other files to get. | |
| 4138 | |
| 4139 @node References | |
| 4140 @chapter References to Non-Free Software and Documentation | |
| 4141 @cindex references to non-free material | |
| 4142 | |
|
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4143 A GNU program should not recommend, promote, or grant legitimacy to |
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4144 the use of any non-free program. Proprietary software is a social and |
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4145 ethical problem, and our aim is to put an end to that problem. We |
| 4958 | 4146 can't stop some people from writing proprietary programs, or stop |
| 4147 other people from using them, but we can and should refuse to | |
|
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4148 advertise them to new potential customers, or to give the public the |
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4149 idea that their existence is ethical. |
| 4958 | 4150 |
| 5566 | 4151 The GNU definition of free software is found on the GNU web site at |
| 9823 | 4152 @url{http://www.gnu.org/@/philosophy/@/free-sw.html}, and the definition |
| 6537 | 4153 of free documentation is found at |
| 9823 | 4154 @url{http://www.gnu.org/@/philosophy/@/free-doc.html}. The terms ``free'' |
|
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4155 and ``non-free'', used in this document, refer to those definitions. |
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4156 |
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4157 A list of important licenses and whether they qualify as free is in |
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4158 @url{http://www.gnu.org/@/licenses/@/license-list.html}. If it is not |
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4159 clear whether a license qualifies as free, please ask the GNU Project |
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4160 by writing to @email{licensing@@gnu.org}. We will answer, and if the |
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4161 license is an important one, we will add it to the list. |
| 4958 | 4162 |
| 4163 When a non-free program or system is well known, you can mention it in | |
| 4164 passing---that is harmless, since users who might want to use it | |
| 4165 probably already know about it. For instance, it is fine to explain | |
| 4166 how to build your package on top of some widely used non-free | |
| 4167 operating system, or how to use it together with some widely used | |
| 4168 non-free program. | |
| 4169 | |
| 4170 However, you should give only the necessary information to help those | |
| 4171 who already use the non-free program to use your program with | |
| 4172 it---don't give, or refer to, any further information about the | |
| 4173 proprietary program, and don't imply that the proprietary program | |
| 4174 enhances your program, or that its existence is in any way a good | |
| 4175 thing. The goal should be that people already using the proprietary | |
| 4176 program will get the advice they need about how to use your free | |
| 4177 program with it, while people who don't already use the proprietary | |
|
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4178 program will not see anything likely to lead them to take an interest |
|
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4179 in it. |
| 4958 | 4180 |
| 4181 If a non-free program or system is obscure in your program's domain, | |
| 4182 your program should not mention or support it at all, since doing so | |
| 4183 would tend to popularize the non-free program more than it popularizes | |
|
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4184 your program. (You cannot hope to find many additional users for your |
|
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4185 program among the users of Foobar, if the existence of Foobar is not |
|
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4186 generally known among people who might want to use your program.) |
| 4958 | 4187 |
| 4188 Sometimes a program is free software in itself but depends on a | |
| 4189 non-free platform in order to run. For instance, many Java programs | |
|
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4190 depend on some non-free Java libraries. To recommend or promote such |
|
4e0536363af3
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4191 a program is to promote the other programs it needs. This is why we |
|
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4192 are careful about listing Java programs in the Free Software |
|
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4193 Directory: we don't want to promote the non-free Java libraries. |
|
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4194 |
|
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4195 We hope this particular problem with Java will be gone by and by, as |
|
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4196 we replace the remaining non-free standard Java libraries with free |
|
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4197 software, but the general principle will remain the same: don't |
|
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4198 recommend, promote or legitimize programs that depend on non-free |
|
4e0536363af3
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|
4199 software to run. |
|
4e0536363af3
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|
4200 |
|
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4201 Some free programs strongly encourage the use of non-free software. A |
|
4e0536363af3
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4202 typical example is @command{mplayer}. It is free software in itself, |
|
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|
4203 and the free code can handle some kinds of files. However, |
|
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|
4204 @command{mplayer} recommends use of non-free codecs for other kinds of |
|
4e0536363af3
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|
4205 files, and users that install @command{mplayer} are very likely to |
|
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|
4206 install those codecs along with it. To recommend @command{mplayer} |
|
4e0536363af3
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|
4207 is, in effect, to promote use of the non-free codecs. |
|
4e0536363af3
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|
4208 |
|
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|
4209 Thus, you should not recommend programs that strongly encourage the |
|
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|
4210 use of non-free software. This is why we do not list |
|
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|
4211 @command{mplayer} in the Free Software Directory. |
| 4958 | 4212 |
| 4213 A GNU package should not refer the user to any non-free documentation | |
| 4214 for free software. Free documentation that can be included in free | |
| 4215 operating systems is essential for completing the GNU system, or any | |
|
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|
4216 free operating system, so encouraging it is a priority; to recommend |
|
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|
4217 use of documentation that we are not allowed to include undermines the |
|
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|
4218 impetus for the community to produce documentation that we can |
|
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4219 include. So GNU packages should never recommend non-free |
| 4958 | 4220 documentation. |
| 4221 | |
| 4222 By contrast, it is ok to refer to journal articles and textbooks in | |
| 4223 the comments of a program for explanation of how it functions, even | |
|
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|
4224 though they are non-free. This is because we don't include such |
| 13440 | 4225 things in the GNU system even if they are free---they are outside the |
|
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|
4226 scope of what a software distribution needs to include. |
| 4958 | 4227 |
| 4228 Referring to a web site that describes or recommends a non-free | |
| 16158 | 4229 program is promoting that program, so please do not make links to (or |
|
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|
4230 mention by name) web sites that contain such material. This policy is |
|
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|
4231 relevant particularly for the web pages for a GNU package. |
|
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|
4232 |
|
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|
4233 Following links from nearly any web site can lead eventually to |
|
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|
4234 non-free software; this is inherent in the nature of the web. So it |
|
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|
4235 makes no sense to criticize a site for having such links. As long as |
|
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|
4236 the site does not itself recommend a non-free program, there is no |
|
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|
4237 need to consider the question of the sites that it links to for other |
|
4e0536363af3
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|
4238 reasons. |
|
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|
4239 |
|
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|
4240 Thus, for example, you should not refer to AT&T's web site if that |
|
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|
4241 recommends AT&T's non-free software packages; you should not refer to |
|
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|
4242 a site that links to AT&T's site presenting it as a place to get some |
|
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changeset
|
4243 non-free program, because that link recommends and legitimizes the |
|
4e0536363af3
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changeset
|
4244 non-free program. However, that a site contains a link to AT&T's web |
|
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changeset
|
4245 site for some other purpose (such as long-distance telephone service) |
|
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|
4246 is not an objection against it. |
| 9115 | 4247 |
| 4248 @node GNU Free Documentation License | |
| 4249 @appendix GNU Free Documentation License | |
| 4250 | |
| 4251 @cindex FDL, GNU Free Documentation License | |
|
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|
4252 @include fdl.texi |
| 4958 | 4253 |
| 4254 @node Index | |
| 4255 @unnumbered Index | |
| 4256 @printindex cp | |
| 4257 | |
| 4258 @bye | |
| 4259 | |
| 4260 Local variables: | |
| 4261 eval: (add-hook 'write-file-hooks 'time-stamp) | |
| 4262 time-stamp-start: "@set lastupdate " | |
| 4263 time-stamp-end: "$" | |
| 4264 time-stamp-format: "%:b %:d, %:y" | |
| 11990 | 4265 compile-command: "cd work.s && make" |
| 4958 | 4266 End: |