Mercurial > hg > octave-kai > gnulib-hg
annotate doc/standards.texi @ 10199:9a94025d6470
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| author | Karl Berry <karl@freefriends.org> |
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| date | Wed, 11 Jun 2008 05:23:13 -0700 |
| parents | b699ce317534 |
| children | 9f20b40ea114 |
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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: | |
| 10199 | 6 @set lastupdate June 10, 2008 |
| 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, |
| 9740 | 30 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software |
| 7910 | 31 Foundation, Inc. |
| 4958 | 32 |
| 33 Permission is granted to copy, distribute and/or modify this document | |
| 7137 | 34 under the terms of the GNU Free Documentation License, Version 1.2 |
| 4958 | 35 or any later version published by the Free Software Foundation; |
| 36 with no Invariant Sections, with no | |
| 37 Front-Cover Texts, and with no Back-Cover Texts. | |
| 38 A copy of the license is included in the section entitled ``GNU | |
| 39 Free Documentation License''. | |
| 40 @end copying | |
| 41 | |
| 42 @titlepage | |
| 43 @title GNU Coding Standards | |
| 44 @author Richard Stallman, et al. | |
| 45 @author last updated @value{lastupdate} | |
| 46 @page | |
| 47 @vskip 0pt plus 1filll | |
| 48 @insertcopying | |
| 49 @end titlepage | |
| 50 | |
| 51 @contents | |
| 52 | |
| 53 @ifnottex | |
| 54 @node Top, Preface, (dir), (dir) | |
| 55 @top Version | |
| 56 | |
| 57 @insertcopying | |
| 58 @end ifnottex | |
| 59 | |
| 60 @menu | |
| 9115 | 61 * Preface:: About the GNU Coding Standards. |
| 62 * Legal Issues:: Keeping free software free. | |
| 63 * Design Advice:: General program design. | |
| 64 * Program Behavior:: Program behavior for all programs | |
| 65 * Writing C:: Making the best use of C. | |
| 66 * Documentation:: Documenting programs. | |
| 67 * Managing Releases:: The release process. | |
| 68 * References:: Mentioning non-free software or documentation. | |
| 69 * GNU Free Documentation License:: Copying and sharing this manual. | |
| 6725 | 70 * Index:: |
| 4958 | 71 |
| 72 @end menu | |
| 73 | |
| 74 @node Preface | |
| 75 @chapter About the GNU Coding Standards | |
| 76 | |
| 77 The GNU Coding Standards were written by Richard Stallman and other GNU | |
| 78 Project volunteers. Their purpose is to make the GNU system clean, | |
| 79 consistent, and easy to install. This document can also be read as a | |
| 80 guide to writing portable, robust and reliable programs. It focuses on | |
| 81 programs written in C, but many of the rules and principles are useful | |
| 82 even if you write in another programming language. The rules often | |
| 83 state reasons for writing in a certain way. | |
| 84 | |
| 85 This release of the GNU Coding Standards was last updated | |
| 86 @value{lastupdate}. | |
| 87 | |
| 88 @cindex where to obtain @code{standards.texi} | |
| 89 @cindex downloading this manual | |
| 90 If you did not obtain this file directly from the GNU project and | |
| 91 recently, please check for a newer version. You can get the GNU | |
| 5301 | 92 Coding Standards from the GNU web server in many |
| 93 different formats, including the Texinfo source, PDF, HTML, DVI, plain | |
| 94 text, and more, at: @uref{http://www.gnu.org/prep/standards/}. | |
| 4958 | 95 |
| 96 Corrections or suggestions for this document should be sent to | |
| 97 @email{bug-standards@@gnu.org}. If you make a suggestion, please include a | |
| 98 suggested new wording for it; our time is limited. We prefer a context | |
| 99 diff to the @file{standards.texi} or @file{make-stds.texi} files, but if | |
| 100 you don't have those files, please mail your suggestion anyway. | |
| 101 | |
| 102 These standards cover the minimum of what is important when writing a | |
| 8453 | 103 GNU package. Likely, the need for additional standards will come up. |
| 4958 | 104 Sometimes, you might suggest that such standards be added to this |
| 105 document. If you think your standards would be generally useful, please | |
| 106 do suggest them. | |
| 107 | |
| 108 You should also set standards for your package on many questions not | |
| 109 addressed or not firmly specified here. The most important point is to | |
| 110 be self-consistent---try to stick to the conventions you pick, and try | |
| 111 to document them as much as possible. That way, your program will be | |
| 112 more maintainable by others. | |
| 113 | |
| 114 The GNU Hello program serves as an example of how to follow the GNU | |
| 6725 | 115 coding standards for a trivial program. |
| 116 @uref{http://www.gnu.org/software/hello/hello.html}. | |
| 4958 | 117 |
| 118 @node Legal Issues | |
| 119 @chapter Keeping Free Software Free | |
| 120 @cindex legal aspects | |
| 121 | |
| 5301 | 122 This chapter discusses how you can make sure that GNU software |
| 4958 | 123 avoids legal difficulties, and other related issues. |
| 124 | |
| 125 @menu | |
| 9115 | 126 * Reading Non-Free Code:: Referring to proprietary programs. |
| 127 * Contributions:: Accepting contributions. | |
| 128 * Trademarks:: How we deal with trademark issues. | |
| 4958 | 129 @end menu |
| 130 | |
| 131 @node Reading Non-Free Code | |
| 132 @section Referring to Proprietary Programs | |
| 133 @cindex proprietary programs | |
| 134 @cindex avoiding proprietary code | |
| 135 | |
| 136 Don't in any circumstances refer to Unix source code for or during | |
| 137 your work on GNU! (Or to any other proprietary programs.) | |
| 138 | |
| 139 If you have a vague recollection of the internals of a Unix program, | |
| 140 this does not absolutely mean you can't write an imitation of it, but | |
| 141 do try to organize the imitation internally along different lines, | |
| 142 because this is likely to make the details of the Unix version | |
| 143 irrelevant and dissimilar to your results. | |
| 144 | |
| 145 For example, Unix utilities were generally optimized to minimize | |
| 146 memory use; if you go for speed instead, your program will be very | |
| 7663 | 147 different. You could keep the entire input file in memory and scan it |
| 4958 | 148 there instead of using stdio. Use a smarter algorithm discovered more |
| 149 recently than the Unix program. Eliminate use of temporary files. Do | |
| 150 it in one pass instead of two (we did this in the assembler). | |
| 151 | |
| 152 Or, on the contrary, emphasize simplicity instead of speed. For some | |
| 153 applications, the speed of today's computers makes simpler algorithms | |
| 154 adequate. | |
| 155 | |
| 156 Or go for generality. For example, Unix programs often have static | |
| 157 tables or fixed-size strings, which make for arbitrary limits; use | |
| 158 dynamic allocation instead. Make sure your program handles NULs and | |
| 159 other funny characters in the input files. Add a programming language | |
| 160 for extensibility and write part of the program in that language. | |
| 161 | |
| 162 Or turn some parts of the program into independently usable libraries. | |
| 163 Or use a simple garbage collector instead of tracking precisely when | |
| 164 to free memory, or use a new GNU facility such as obstacks. | |
| 165 | |
| 166 @node Contributions | |
| 167 @section Accepting Contributions | |
| 168 @cindex legal papers | |
| 169 @cindex accepting contributions | |
| 170 | |
| 171 If the program you are working on is copyrighted by the Free Software | |
| 172 Foundation, then when someone else sends you a piece of code to add to | |
| 173 the program, we need legal papers to use it---just as we asked you to | |
| 174 sign papers initially. @emph{Each} person who makes a nontrivial | |
| 175 contribution to a program must sign some sort of legal papers in order | |
| 176 for us to have clear title to the program; the main author alone is not | |
| 177 enough. | |
| 178 | |
| 179 So, before adding in any contributions from other people, please tell | |
| 180 us, so we can arrange to get the papers. Then wait until we tell you | |
| 181 that we have received the signed papers, before you actually use the | |
| 182 contribution. | |
| 183 | |
| 184 This applies both before you release the program and afterward. If | |
| 185 you receive diffs to fix a bug, and they make significant changes, we | |
| 186 need legal papers for that change. | |
| 187 | |
| 188 This also applies to comments and documentation files. For copyright | |
| 189 law, comments and code are just text. Copyright applies to all kinds of | |
| 190 text, so we need legal papers for all kinds. | |
| 191 | |
| 192 We know it is frustrating to ask for legal papers; it's frustrating for | |
| 193 us as well. But if you don't wait, you are going out on a limb---for | |
| 194 example, what if the contributor's employer won't sign a disclaimer? | |
| 195 You might have to take that code out again! | |
| 196 | |
| 197 You don't need papers for changes of a few lines here or there, since | |
| 198 they are not significant for copyright purposes. Also, you don't need | |
| 199 papers if all you get from the suggestion is some ideas, not actual code | |
| 5301 | 200 which you use. For example, if someone sent you one implementation, but |
| 4958 | 201 you write a different implementation of the same idea, you don't need to |
| 202 get papers. | |
| 203 | |
| 204 The very worst thing is if you forget to tell us about the other | |
| 205 contributor. We could be very embarrassed in court some day as a | |
| 206 result. | |
| 207 | |
| 208 We have more detailed advice for maintainers of programs; if you have | |
| 209 reached the stage of actually maintaining a program for GNU (whether | |
| 5301 | 210 released or not), please ask us for a copy. It is also available |
| 211 online for your perusal: @uref{http://www.gnu.org/prep/maintain/}. | |
| 4958 | 212 |
| 213 @node Trademarks | |
| 214 @section Trademarks | |
| 215 @cindex trademarks | |
| 216 | |
| 217 Please do not include any trademark acknowledgements in GNU software | |
| 218 packages or documentation. | |
| 219 | |
| 220 Trademark acknowledgements are the statements that such-and-such is a | |
| 221 trademark of so-and-so. The GNU Project has no objection to the basic | |
| 6725 | 222 idea of trademarks, but these acknowledgements feel like kowtowing, |
| 4958 | 223 and there is no legal requirement for them, so we don't use them. |
| 224 | |
| 225 What is legally required, as regards other people's trademarks, is to | |
| 226 avoid using them in ways which a reader might reasonably understand as | |
| 227 naming or labeling our own programs or activities. For example, since | |
| 228 ``Objective C'' is (or at least was) a trademark, we made sure to say | |
| 229 that we provide a ``compiler for the Objective C language'' rather | |
| 230 than an ``Objective C compiler''. The latter would have been meant as | |
| 231 a shorter way of saying the former, but it does not explicitly state | |
| 232 the relationship, so it could be misinterpreted as using ``Objective | |
| 233 C'' as a label for the compiler rather than for the language. | |
| 234 | |
| 235 Please don't use ``win'' as an abbreviation for Microsoft Windows in | |
| 236 GNU software or documentation. In hacker terminology, calling | |
| 5909 | 237 something a ``win'' is a form of praise. If you wish to praise |
| 4958 | 238 Microsoft Windows when speaking on your own, by all means do so, but |
| 5909 | 239 not in GNU software. Usually we write the name ``Windows'' in full, |
| 4958 | 240 but when brevity is very important (as in file names and sometimes |
| 241 symbol names), we abbreviate it to ``w''. For instance, the files and | |
| 242 functions in Emacs that deal with Windows start with @samp{w32}. | |
| 243 | |
| 244 @node Design Advice | |
| 245 @chapter General Program Design | |
| 246 @cindex program design | |
| 247 | |
| 5301 | 248 This chapter discusses some of the issues you should take into |
| 4958 | 249 account when designing your program. |
| 250 | |
| 251 @c Standard or ANSI C | |
| 252 @c | |
| 253 @c In 1989 the American National Standards Institute (ANSI) standardized | |
| 254 @c C as standard X3.159-1989. In December of that year the | |
| 255 @c International Standards Organization ISO adopted the ANSI C standard | |
| 256 @c making minor changes. In 1990 ANSI then re-adopted ISO standard | |
| 257 @c C. This version of C is known as either ANSI C or Standard C. | |
| 258 | |
| 259 @c A major revision of the C Standard appeared in 1999. | |
| 260 | |
| 261 @menu | |
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262 * Source Language:: Which languages to use. |
| 9115 | 263 * Compatibility:: Compatibility with other implementations. |
| 264 * Using Extensions:: Using non-standard features. | |
| 265 * Standard C:: Using standard C features. | |
| 266 * Conditional Compilation:: Compiling code only if a conditional is true. | |
| 4958 | 267 @end menu |
| 268 | |
| 269 @node Source Language | |
| 270 @section Which Languages to Use | |
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271 @cindex programming languages |
| 4958 | 272 |
| 273 When you want to use a language that gets compiled and runs at high | |
| 274 speed, the best language to use is C. Using another language is like | |
| 275 using a non-standard feature: it will cause trouble for users. Even if | |
| 276 GCC supports the other language, users may find it inconvenient to have | |
| 277 to install the compiler for that other language in order to build your | |
| 278 program. For example, if you write your program in C++, people will | |
| 279 have to install the GNU C++ compiler in order to compile your program. | |
| 280 | |
| 281 C has one other advantage over C++ and other compiled languages: more | |
| 282 people know C, so more people will find it easy to read and modify the | |
| 283 program if it is written in C. | |
| 284 | |
| 285 So in general it is much better to use C, rather than the | |
| 286 comparable alternatives. | |
| 287 | |
| 288 But there are two exceptions to that conclusion: | |
| 289 | |
| 290 @itemize @bullet | |
| 291 @item | |
| 292 It is no problem to use another language to write a tool specifically | |
| 293 intended for use with that language. That is because the only people | |
| 294 who want to build the tool will be those who have installed the other | |
| 295 language anyway. | |
| 296 | |
| 297 @item | |
| 298 If an application is of interest only to a narrow part of the community, | |
| 299 then the question of which language it is written in has less effect on | |
| 300 other people, so you may as well please yourself. | |
| 301 @end itemize | |
| 302 | |
| 303 Many programs are designed to be extensible: they include an interpreter | |
| 304 for a language that is higher level than C. Often much of the program | |
| 305 is written in that language, too. The Emacs editor pioneered this | |
| 306 technique. | |
| 307 | |
| 10037 | 308 @cindex Guile |
| 309 @cindex GNOME and Guile | |
| 310 The standard extensibility interpreter for GNU software is Guile | |
| 9823 | 311 (@uref{http://www.gnu.org/@/software/@/guile/}), which implements the |
| 10037 | 312 language Scheme (an especially clean and simple dialect of Lisp). |
| 313 Guile also includes bindings for GTK+/GNOME, making it practical to | |
| 314 write modern GUI functionality within Guile. We don't reject programs | |
| 315 written in other ``scripting languages'' such as Perl and Python, but | |
| 316 using Guile is very important for the overall consistency of the GNU | |
| 317 system. | |
| 318 | |
| 4958 | 319 |
| 320 @node Compatibility | |
| 321 @section Compatibility with Other Implementations | |
| 322 @cindex compatibility with C and @sc{posix} standards | |
| 323 @cindex @sc{posix} compatibility | |
| 324 | |
| 325 With occasional exceptions, utility programs and libraries for GNU | |
| 326 should be upward compatible with those in Berkeley Unix, and upward | |
| 327 compatible with Standard C if Standard C specifies their | |
| 328 behavior, and upward compatible with @sc{posix} if @sc{posix} specifies | |
| 329 their behavior. | |
| 330 | |
| 331 When these standards conflict, it is useful to offer compatibility | |
| 332 modes for each of them. | |
| 333 | |
| 334 @cindex options for compatibility | |
| 335 Standard C and @sc{posix} prohibit many kinds of extensions. Feel | |
| 336 free to make the extensions anyway, and include a @samp{--ansi}, | |
| 337 @samp{--posix}, or @samp{--compatible} option to turn them off. | |
| 338 However, if the extension has a significant chance of breaking any real | |
| 339 programs or scripts, then it is not really upward compatible. So you | |
| 340 should try to redesign its interface to make it upward compatible. | |
| 341 | |
| 342 @cindex @code{POSIXLY_CORRECT}, environment variable | |
| 343 Many GNU programs suppress extensions that conflict with @sc{posix} if the | |
| 344 environment variable @code{POSIXLY_CORRECT} is defined (even if it is | |
| 345 defined with a null value). Please make your program recognize this | |
| 346 variable if appropriate. | |
| 347 | |
| 348 When a feature is used only by users (not by programs or command | |
| 349 files), and it is done poorly in Unix, feel free to replace it | |
| 350 completely with something totally different and better. (For example, | |
| 351 @code{vi} is replaced with Emacs.) But it is nice to offer a compatible | |
| 352 feature as well. (There is a free @code{vi} clone, so we offer it.) | |
| 353 | |
| 354 Additional useful features are welcome regardless of whether | |
| 355 there is any precedent for them. | |
| 356 | |
| 357 @node Using Extensions | |
| 358 @section Using Non-standard Features | |
| 359 @cindex non-standard extensions | |
| 360 | |
| 361 Many GNU facilities that already exist support a number of convenient | |
| 362 extensions over the comparable Unix facilities. Whether to use these | |
| 363 extensions in implementing your program is a difficult question. | |
| 364 | |
| 365 On the one hand, using the extensions can make a cleaner program. | |
| 366 On the other hand, people will not be able to build the program | |
| 367 unless the other GNU tools are available. This might cause the | |
| 368 program to work on fewer kinds of machines. | |
| 369 | |
| 370 With some extensions, it might be easy to provide both alternatives. | |
| 371 For example, you can define functions with a ``keyword'' @code{INLINE} | |
| 372 and define that as a macro to expand into either @code{inline} or | |
| 373 nothing, depending on the compiler. | |
| 374 | |
| 375 In general, perhaps it is best not to use the extensions if you can | |
| 376 straightforwardly do without them, but to use the extensions if they | |
| 377 are a big improvement. | |
| 378 | |
| 379 An exception to this rule are the large, established programs (such as | |
| 380 Emacs) which run on a great variety of systems. Using GNU extensions in | |
| 381 such programs would make many users unhappy, so we don't do that. | |
| 382 | |
| 383 Another exception is for programs that are used as part of compilation: | |
| 384 anything that must be compiled with other compilers in order to | |
| 385 bootstrap the GNU compilation facilities. If these require the GNU | |
| 386 compiler, then no one can compile them without having them installed | |
| 387 already. That would be extremely troublesome in certain cases. | |
| 388 | |
| 389 @node Standard C | |
| 390 @section Standard C and Pre-Standard C | |
| 391 @cindex @sc{ansi} C standard | |
| 392 | |
| 393 1989 Standard C is widespread enough now that it is ok to use its | |
| 394 features in new programs. There is one exception: do not ever use the | |
| 395 ``trigraph'' feature of Standard C. | |
| 396 | |
| 397 1999 Standard C is not widespread yet, so please do not require its | |
| 398 features in programs. It is ok to use its features if they are present. | |
| 399 | |
| 400 However, it is easy to support pre-standard compilers in most programs, | |
| 401 so if you know how to do that, feel free. If a program you are | |
| 402 maintaining has such support, you should try to keep it working. | |
| 403 | |
| 404 @cindex function prototypes | |
| 405 To support pre-standard C, instead of writing function definitions in | |
| 406 standard prototype form, | |
| 407 | |
| 408 @example | |
| 409 int | |
| 410 foo (int x, int y) | |
| 411 @dots{} | |
| 412 @end example | |
| 413 | |
| 414 @noindent | |
| 415 write the definition in pre-standard style like this, | |
| 416 | |
| 417 @example | |
| 418 int | |
| 419 foo (x, y) | |
| 420 int x, y; | |
| 421 @dots{} | |
| 422 @end example | |
| 423 | |
| 424 @noindent | |
| 425 and use a separate declaration to specify the argument prototype: | |
| 426 | |
| 427 @example | |
| 428 int foo (int, int); | |
| 429 @end example | |
| 430 | |
| 431 You need such a declaration anyway, in a header file, to get the benefit | |
| 432 of prototypes in all the files where the function is called. And once | |
| 433 you have the declaration, you normally lose nothing by writing the | |
| 434 function definition in the pre-standard style. | |
| 435 | |
| 436 This technique does not work for integer types narrower than @code{int}. | |
| 437 If you think of an argument as being of a type narrower than @code{int}, | |
| 438 declare it as @code{int} instead. | |
| 439 | |
| 440 There are a few special cases where this technique is hard to use. For | |
| 441 example, if a function argument needs to hold the system type | |
| 442 @code{dev_t}, you run into trouble, because @code{dev_t} is shorter than | |
| 443 @code{int} on some machines; but you cannot use @code{int} instead, | |
| 444 because @code{dev_t} is wider than @code{int} on some machines. There | |
| 445 is no type you can safely use on all machines in a non-standard | |
| 446 definition. The only way to support non-standard C and pass such an | |
| 447 argument is to check the width of @code{dev_t} using Autoconf and choose | |
| 448 the argument type accordingly. This may not be worth the trouble. | |
| 449 | |
| 450 In order to support pre-standard compilers that do not recognize | |
| 451 prototypes, you may want to use a preprocessor macro like this: | |
| 452 | |
| 453 @example | |
| 454 /* Declare the prototype for a general external function. */ | |
| 455 #if defined (__STDC__) || defined (WINDOWSNT) | |
| 456 #define P_(proto) proto | |
| 457 #else | |
| 458 #define P_(proto) () | |
| 459 #endif | |
| 460 @end example | |
| 461 | |
| 462 @node Conditional Compilation | |
| 463 @section Conditional Compilation | |
| 464 | |
| 465 When supporting configuration options already known when building your | |
| 466 program we prefer using @code{if (... )} over conditional compilation, | |
| 467 as in the former case the compiler is able to perform more extensive | |
| 468 checking of all possible code paths. | |
| 469 | |
| 470 For example, please write | |
| 471 | |
| 472 @smallexample | |
| 473 if (HAS_FOO) | |
| 474 ... | |
| 475 else | |
| 476 ... | |
| 477 @end smallexample | |
| 478 | |
| 479 @noindent | |
| 480 instead of: | |
| 481 | |
| 482 @smallexample | |
| 483 #ifdef HAS_FOO | |
| 484 ... | |
| 485 #else | |
| 486 ... | |
| 487 #endif | |
| 488 @end smallexample | |
| 489 | |
| 490 A modern compiler such as GCC will generate exactly the same code in | |
| 491 both cases, and we have been using similar techniques with good success | |
| 492 in several projects. Of course, the former method assumes that | |
| 493 @code{HAS_FOO} is defined as either 0 or 1. | |
| 494 | |
| 495 While this is not a silver bullet solving all portability problems, | |
| 496 and is not always appropriate, following this policy would have saved | |
| 497 GCC developers many hours, or even days, per year. | |
| 498 | |
| 499 In the case of function-like macros like @code{REVERSIBLE_CC_MODE} in | |
| 500 GCC which cannot be simply used in @code{if( ...)} statements, there is | |
| 501 an easy workaround. Simply introduce another macro | |
| 502 @code{HAS_REVERSIBLE_CC_MODE} as in the following example: | |
| 503 | |
| 504 @smallexample | |
| 505 #ifdef REVERSIBLE_CC_MODE | |
| 506 #define HAS_REVERSIBLE_CC_MODE 1 | |
| 507 #else | |
| 508 #define HAS_REVERSIBLE_CC_MODE 0 | |
| 509 #endif | |
| 510 @end smallexample | |
| 511 | |
| 512 @node Program Behavior | |
| 513 @chapter Program Behavior for All Programs | |
| 514 | |
| 5301 | 515 This chapter describes conventions for writing robust |
| 4958 | 516 software. It also describes general standards for error messages, the |
| 517 command line interface, and how libraries should behave. | |
| 518 | |
| 519 @menu | |
| 6629 | 520 * Non-GNU Standards:: We consider standards such as POSIX; |
| 521 we don't "obey" them. | |
| 9115 | 522 * Semantics:: Writing robust programs. |
| 523 * Libraries:: Library behavior. | |
| 524 * Errors:: Formatting error messages. | |
| 525 * User Interfaces:: Standards about interfaces generally. | |
| 526 * Graphical Interfaces:: Standards for graphical interfaces. | |
| 527 * Command-Line Interfaces:: Standards for command line interfaces. | |
| 528 * Option Table:: Table of long options. | |
| 529 * Memory Usage:: When and how to care about memory needs. | |
| 530 * File Usage:: Which files to use, and where. | |
| 4958 | 531 @end menu |
| 532 | |
| 6629 | 533 @node Non-GNU Standards |
| 534 @section Non-GNU Standards | |
| 535 | |
| 536 The GNU Project regards standards published by other organizations as | |
| 537 suggestions, not orders. We consider those standards, but we do not | |
| 538 ``obey'' them. In developing a GNU program, you should implement | |
| 539 an outside standard's specifications when that makes the GNU system | |
| 540 better overall in an objective sense. When it doesn't, you shouldn't. | |
| 541 | |
| 542 In most cases, following published standards is convenient for | |
| 543 users---it means that their programs or scripts will work more | |
| 544 portably. For instance, GCC implements nearly all the features of | |
| 545 Standard C as specified by that standard. C program developers would | |
| 546 be unhappy if it did not. And GNU utilities mostly follow | |
| 547 specifications of POSIX.2; shell script writers and users would be | |
| 548 unhappy if our programs were incompatible. | |
| 549 | |
| 550 But we do not follow either of these specifications rigidly, and there | |
| 551 are specific points on which we decided not to follow them, so as to | |
| 552 make the GNU system better for users. | |
| 553 | |
| 554 For instance, Standard C says that nearly all extensions to C are | |
| 555 prohibited. How silly! GCC implements many extensions, some of which | |
| 556 were later adopted as part of the standard. If you want these | |
| 557 constructs to give an error message as ``required'' by the standard, | |
| 558 you must specify @samp{--pedantic}, which was implemented only so that | |
| 559 we can say ``GCC is a 100% implementation of the standard,'' not | |
| 560 because there is any reason to actually use it. | |
| 561 | |
| 562 POSIX.2 specifies that @samp{df} and @samp{du} must output sizes by | |
| 563 default in units of 512 bytes. What users want is units of 1k, so | |
| 564 that is what we do by default. If you want the ridiculous behavior | |
| 565 ``required'' by POSIX, you must set the environment variable | |
| 566 @samp{POSIXLY_CORRECT} (which was originally going to be named | |
| 567 @samp{POSIX_ME_HARDER}). | |
| 568 | |
| 569 GNU utilities also depart from the letter of the POSIX.2 specification | |
| 570 when they support long-named command-line options, and intermixing | |
| 571 options with ordinary arguments. This minor incompatibility with | |
| 572 POSIX is never a problem in practice, and it is very useful. | |
| 573 | |
| 574 In particular, don't reject a new feature, or remove an old one, | |
| 575 merely because a standard says it is ``forbidden'' or ``deprecated.'' | |
| 576 | |
| 4958 | 577 @node Semantics |
| 578 @section Writing Robust Programs | |
| 579 | |
| 580 @cindex arbitrary limits on data | |
| 581 Avoid arbitrary limits on the length or number of @emph{any} data | |
| 582 structure, including file names, lines, files, and symbols, by allocating | |
| 583 all data structures dynamically. In most Unix utilities, ``long lines | |
| 584 are silently truncated''. This is not acceptable in a GNU utility. | |
| 585 | |
| 586 @cindex @code{NUL} characters | |
| 587 Utilities reading files should not drop NUL characters, or any other | |
| 588 nonprinting characters @emph{including those with codes above 0177}. | |
| 589 The only sensible exceptions would be utilities specifically intended | |
| 590 for interface to certain types of terminals or printers | |
| 591 that can't handle those characters. | |
| 592 Whenever possible, try to make programs work properly with | |
| 593 sequences of bytes that represent multibyte characters, using encodings | |
| 594 such as UTF-8 and others. | |
| 595 | |
| 596 @cindex error messages | |
| 597 Check every system call for an error return, unless you know you wish to | |
| 598 ignore errors. Include the system error text (from @code{perror} or | |
| 599 equivalent) in @emph{every} error message resulting from a failing | |
| 600 system call, as well as the name of the file if any and the name of the | |
| 601 utility. Just ``cannot open foo.c'' or ``stat failed'' is not | |
| 602 sufficient. | |
| 603 | |
| 604 @cindex @code{malloc} return value | |
| 605 @cindex memory allocation failure | |
| 606 Check every call to @code{malloc} or @code{realloc} to see if it | |
| 607 returned zero. Check @code{realloc} even if you are making the block | |
| 608 smaller; in a system that rounds block sizes to a power of 2, | |
| 609 @code{realloc} may get a different block if you ask for less space. | |
| 610 | |
| 611 In Unix, @code{realloc} can destroy the storage block if it returns | |
| 612 zero. GNU @code{realloc} does not have this bug: if it fails, the | |
| 613 original block is unchanged. Feel free to assume the bug is fixed. If | |
| 614 you wish to run your program on Unix, and wish to avoid lossage in this | |
| 615 case, you can use the GNU @code{malloc}. | |
| 616 | |
| 617 You must expect @code{free} to alter the contents of the block that was | |
| 618 freed. Anything you want to fetch from the block, you must fetch before | |
| 619 calling @code{free}. | |
| 620 | |
| 621 If @code{malloc} fails in a noninteractive program, make that a fatal | |
| 622 error. In an interactive program (one that reads commands from the | |
| 623 user), it is better to abort the command and return to the command | |
| 624 reader loop. This allows the user to kill other processes to free up | |
| 625 virtual memory, and then try the command again. | |
| 626 | |
| 627 @cindex command-line arguments, decoding | |
| 628 Use @code{getopt_long} to decode arguments, unless the argument syntax | |
| 629 makes this unreasonable. | |
| 630 | |
| 631 When static storage is to be written in during program execution, use | |
| 632 explicit C code to initialize it. Reserve C initialized declarations | |
| 633 for data that will not be changed. | |
| 634 @c ADR: why? | |
| 635 | |
| 636 Try to avoid low-level interfaces to obscure Unix data structures (such | |
| 637 as file directories, utmp, or the layout of kernel memory), since these | |
| 638 are less likely to work compatibly. If you need to find all the files | |
| 639 in a directory, use @code{readdir} or some other high-level interface. | |
| 640 These are supported compatibly by GNU. | |
| 641 | |
| 642 @cindex signal handling | |
| 643 The preferred signal handling facilities are the BSD variant of | |
| 644 @code{signal}, and the @sc{posix} @code{sigaction} function; the | |
| 645 alternative USG @code{signal} interface is an inferior design. | |
| 646 | |
| 647 Nowadays, using the @sc{posix} signal functions may be the easiest way | |
| 648 to make a program portable. If you use @code{signal}, then on GNU/Linux | |
| 649 systems running GNU libc version 1, you should include | |
| 650 @file{bsd/signal.h} instead of @file{signal.h}, so as to get BSD | |
| 651 behavior. It is up to you whether to support systems where | |
| 652 @code{signal} has only the USG behavior, or give up on them. | |
| 653 | |
| 654 @cindex impossible conditions | |
| 655 In error checks that detect ``impossible'' conditions, just abort. | |
| 656 There is usually no point in printing any message. These checks | |
| 657 indicate the existence of bugs. Whoever wants to fix the bugs will have | |
| 658 to read the source code and run a debugger. So explain the problem with | |
| 659 comments in the source. The relevant data will be in variables, which | |
| 660 are easy to examine with the debugger, so there is no point moving them | |
| 661 elsewhere. | |
| 662 | |
| 663 Do not use a count of errors as the exit status for a program. | |
| 664 @emph{That does not work}, because exit status values are limited to 8 | |
| 665 bits (0 through 255). A single run of the program might have 256 | |
| 666 errors; if you try to return 256 as the exit status, the parent process | |
| 667 will see 0 as the status, and it will appear that the program succeeded. | |
| 668 | |
| 669 @cindex temporary files | |
| 670 @cindex @code{TMPDIR} environment variable | |
| 671 If you make temporary files, check the @code{TMPDIR} environment | |
| 672 variable; if that variable is defined, use the specified directory | |
| 673 instead of @file{/tmp}. | |
| 674 | |
| 675 In addition, be aware that there is a possible security problem when | |
| 676 creating temporary files in world-writable directories. In C, you can | |
| 677 avoid this problem by creating temporary files in this manner: | |
| 678 | |
| 679 @example | |
| 680 fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0600); | |
| 681 @end example | |
| 682 | |
| 683 @noindent | |
| 684 or by using the @code{mkstemps} function from libiberty. | |
| 685 | |
| 686 In bash, use @code{set -C} to avoid this problem. | |
| 687 | |
| 688 @node Libraries | |
| 689 @section Library Behavior | |
| 690 @cindex libraries | |
| 691 | |
| 692 Try to make library functions reentrant. If they need to do dynamic | |
| 693 storage allocation, at least try to avoid any nonreentrancy aside from | |
| 694 that of @code{malloc} itself. | |
| 695 | |
| 696 Here are certain name conventions for libraries, to avoid name | |
| 697 conflicts. | |
| 698 | |
| 699 Choose a name prefix for the library, more than two characters long. | |
| 700 All external function and variable names should start with this | |
| 701 prefix. In addition, there should only be one of these in any given | |
| 702 library member. This usually means putting each one in a separate | |
| 703 source file. | |
| 704 | |
| 705 An exception can be made when two external symbols are always used | |
| 706 together, so that no reasonable program could use one without the | |
| 707 other; then they can both go in the same file. | |
| 708 | |
| 709 External symbols that are not documented entry points for the user | |
| 710 should have names beginning with @samp{_}. The @samp{_} should be | |
| 711 followed by the chosen name prefix for the library, to prevent | |
| 712 collisions with other libraries. These can go in the same files with | |
| 713 user entry points if you like. | |
| 714 | |
| 715 Static functions and variables can be used as you like and need not | |
| 716 fit any naming convention. | |
| 717 | |
| 718 @node Errors | |
| 719 @section Formatting Error Messages | |
| 720 @cindex formatting error messages | |
| 721 @cindex error messages, formatting | |
| 722 | |
| 723 Error messages from compilers should look like this: | |
| 724 | |
| 725 @example | |
| 726 @var{source-file-name}:@var{lineno}: @var{message} | |
| 727 @end example | |
| 728 | |
| 729 @noindent | |
| 730 If you want to mention the column number, use one of these formats: | |
| 731 | |
| 732 @example | |
| 733 @var{source-file-name}:@var{lineno}:@var{column}: @var{message} | |
| 6725 | 734 @var{source-file-name}:@var{lineno}.@var{column}: @var{message} |
| 4958 | 735 |
| 736 @end example | |
| 737 | |
| 738 @noindent | |
| 739 Line numbers should start from 1 at the beginning of the file, and | |
| 740 column numbers should start from 1 at the beginning of the line. (Both | |
| 741 of these conventions are chosen for compatibility.) Calculate column | |
| 742 numbers assuming that space and all ASCII printing characters have | |
| 743 equal width, and assuming tab stops every 8 columns. | |
| 744 | |
| 745 The error message can also give both the starting and ending positions | |
| 746 of the erroneous text. There are several formats so that you can | |
| 747 avoid redundant information such as a duplicate line number. | |
| 748 Here are the possible formats: | |
| 749 | |
| 750 @example | |
| 751 @var{source-file-name}:@var{lineno-1}.@var{column-1}-@var{lineno-2}.@var{column-2}: @var{message} | |
| 752 @var{source-file-name}:@var{lineno-1}.@var{column-1}-@var{column-2}: @var{message} | |
| 753 @var{source-file-name}:@var{lineno-1}-@var{lineno-2}: @var{message} | |
| 754 @end example | |
| 755 | |
| 756 @noindent | |
| 757 When an error is spread over several files, you can use this format: | |
| 758 | |
| 759 @example | |
| 760 @var{file-1}:@var{lineno-1}.@var{column-1}-@var{file-2}:@var{lineno-2}.@var{column-2}: @var{message} | |
| 761 @end example | |
| 762 | |
| 763 Error messages from other noninteractive programs should look like this: | |
| 764 | |
| 765 @example | |
| 766 @var{program}:@var{source-file-name}:@var{lineno}: @var{message} | |
| 767 @end example | |
| 768 | |
| 769 @noindent | |
| 770 when there is an appropriate source file, or like this: | |
| 771 | |
| 772 @example | |
| 773 @var{program}: @var{message} | |
| 774 @end example | |
| 775 | |
| 776 @noindent | |
| 777 when there is no relevant source file. | |
| 778 | |
| 779 If you want to mention the column number, use this format: | |
| 780 | |
| 781 @example | |
| 782 @var{program}:@var{source-file-name}:@var{lineno}:@var{column}: @var{message} | |
| 783 @end example | |
| 784 | |
| 785 In an interactive program (one that is reading commands from a | |
| 786 terminal), it is better not to include the program name in an error | |
| 787 message. The place to indicate which program is running is in the | |
| 788 prompt or with the screen layout. (When the same program runs with | |
| 789 input from a source other than a terminal, it is not interactive and | |
| 790 would do best to print error messages using the noninteractive style.) | |
| 791 | |
| 792 The string @var{message} should not begin with a capital letter when | |
| 793 it follows a program name and/or file name, because that isn't the | |
| 794 beginning of a sentence. (The sentence conceptually starts at the | |
| 795 beginning of the line.) Also, it should not end with a period. | |
| 796 | |
| 797 Error messages from interactive programs, and other messages such as | |
| 798 usage messages, should start with a capital letter. But they should not | |
| 799 end with a period. | |
| 800 | |
| 801 @node User Interfaces | |
| 802 @section Standards for Interfaces Generally | |
| 803 | |
| 804 @cindex program name and its behavior | |
| 805 @cindex behavior, dependent on program's name | |
| 806 Please don't make the behavior of a utility depend on the name used | |
| 807 to invoke it. It is useful sometimes to make a link to a utility | |
| 808 with a different name, and that should not change what it does. | |
| 809 | |
| 810 Instead, use a run time option or a compilation switch or both | |
| 811 to select among the alternate behaviors. | |
| 812 | |
| 813 @cindex output device and program's behavior | |
| 814 Likewise, please don't make the behavior of the program depend on the | |
| 815 type of output device it is used with. Device independence is an | |
| 816 important principle of the system's design; do not compromise it merely | |
| 817 to save someone from typing an option now and then. (Variation in error | |
| 818 message syntax when using a terminal is ok, because that is a side issue | |
| 819 that people do not depend on.) | |
| 820 | |
| 821 If you think one behavior is most useful when the output is to a | |
| 822 terminal, and another is most useful when the output is a file or a | |
| 823 pipe, then it is usually best to make the default behavior the one that | |
| 824 is useful with output to a terminal, and have an option for the other | |
| 825 behavior. | |
| 826 | |
| 827 Compatibility requires certain programs to depend on the type of output | |
| 828 device. It would be disastrous if @code{ls} or @code{sh} did not do so | |
| 829 in the way all users expect. In some of these cases, we supplement the | |
| 830 program with a preferred alternate version that does not depend on the | |
| 831 output device type. For example, we provide a @code{dir} program much | |
| 832 like @code{ls} except that its default output format is always | |
| 833 multi-column format. | |
| 834 | |
| 9019 | 835 |
| 4958 | 836 @node Graphical Interfaces |
| 837 @section Standards for Graphical Interfaces | |
| 838 @cindex graphical user interface | |
| 839 | |
| 840 @cindex gtk+ | |
| 841 When you write a program that provides a graphical user interface, | |
| 842 please make it work with X Windows and the GTK+ toolkit unless the | |
| 843 functionality specifically requires some alternative (for example, | |
| 844 ``displaying jpeg images while in console mode''). | |
| 845 | |
| 846 In addition, please provide a command-line interface to control the | |
| 847 functionality. (In many cases, the graphical user interface can be a | |
| 848 separate program which invokes the command-line program.) This is | |
| 849 so that the same jobs can be done from scripts. | |
| 850 | |
| 851 @cindex corba | |
| 852 @cindex gnome | |
| 853 Please also consider providing a CORBA interface (for use from GNOME), a | |
| 854 library interface (for use from C), and perhaps a keyboard-driven | |
| 855 console interface (for use by users from console mode). Once you are | |
| 856 doing the work to provide the functionality and the graphical interface, | |
| 857 these won't be much extra work. | |
| 858 | |
| 9019 | 859 |
| 4958 | 860 @node Command-Line Interfaces |
| 861 @section Standards for Command Line Interfaces | |
| 862 @cindex command-line interface | |
| 863 | |
| 864 @findex getopt | |
| 865 It is a good idea to follow the @sc{posix} guidelines for the | |
| 866 command-line options of a program. The easiest way to do this is to use | |
| 867 @code{getopt} to parse them. Note that the GNU version of @code{getopt} | |
| 868 will normally permit options anywhere among the arguments unless the | |
| 869 special argument @samp{--} is used. This is not what @sc{posix} | |
| 870 specifies; it is a GNU extension. | |
| 871 | |
| 872 @cindex long-named options | |
| 873 Please define long-named options that are equivalent to the | |
| 874 single-letter Unix-style options. We hope to make GNU more user | |
| 875 friendly this way. This is easy to do with the GNU function | |
| 876 @code{getopt_long}. | |
| 877 | |
| 878 One of the advantages of long-named options is that they can be | |
| 879 consistent from program to program. For example, users should be able | |
| 880 to expect the ``verbose'' option of any GNU program which has one, to be | |
| 881 spelled precisely @samp{--verbose}. To achieve this uniformity, look at | |
| 882 the table of common long-option names when you choose the option names | |
| 883 for your program (@pxref{Option Table}). | |
| 884 | |
| 885 It is usually a good idea for file names given as ordinary arguments to | |
| 886 be input files only; any output files would be specified using options | |
| 887 (preferably @samp{-o} or @samp{--output}). Even if you allow an output | |
| 888 file name as an ordinary argument for compatibility, try to provide an | |
| 889 option as another way to specify it. This will lead to more consistency | |
| 6946 | 890 among GNU utilities, and fewer idiosyncrasies for users to remember. |
| 4958 | 891 |
| 892 @cindex standard command-line options | |
| 893 @cindex options, standard command-line | |
| 894 @cindex CGI programs, standard options for | |
| 895 @cindex PATH_INFO, specifying standard options as | |
| 896 All programs should support two standard options: @samp{--version} | |
| 897 and @samp{--help}. CGI programs should accept these as command-line | |
| 898 options, and also if given as the @env{PATH_INFO}; for instance, | |
| 899 visiting @url{http://example.org/p.cgi/--help} in a browser should | |
| 5909 | 900 output the same information as invoking @samp{p.cgi --help} from the |
| 4958 | 901 command line. |
| 902 | |
| 9019 | 903 @menu |
| 904 * --version:: The standard output for --version. | |
| 905 * --help:: The standard output for --help. | |
| 906 @end menu | |
| 907 | |
| 908 @node --version | |
| 909 @subsection @option{--version} | |
| 910 | |
| 911 @cindex @samp{--version} output | |
| 912 | |
| 913 The standard @code{--version} option should direct the program to | |
| 914 print information about its name, version, origin and legal status, | |
| 915 all on standard output, and then exit successfully. Other options and | |
| 916 arguments should be ignored once this is seen, and the program should | |
| 917 not perform its normal function. | |
| 4958 | 918 |
| 919 @cindex canonical name of a program | |
| 920 @cindex program's canonical name | |
| 921 The first line is meant to be easy for a program to parse; the version | |
| 922 number proper starts after the last space. In addition, it contains | |
| 923 the canonical name for this program, in this format: | |
| 924 | |
| 925 @example | |
| 926 GNU Emacs 19.30 | |
| 927 @end example | |
| 928 | |
| 929 @noindent | |
| 930 The program's name should be a constant string; @emph{don't} compute it | |
| 931 from @code{argv[0]}. The idea is to state the standard or canonical | |
| 932 name for the program, not its file name. There are other ways to find | |
| 933 out the precise file name where a command is found in @code{PATH}. | |
| 934 | |
| 935 If the program is a subsidiary part of a larger package, mention the | |
| 936 package name in parentheses, like this: | |
| 937 | |
| 938 @example | |
| 939 emacsserver (GNU Emacs) 19.30 | |
| 940 @end example | |
| 941 | |
| 942 @noindent | |
| 943 If the package has a version number which is different from this | |
| 944 program's version number, you can mention the package version number | |
| 945 just before the close-parenthesis. | |
| 946 | |
| 9019 | 947 If you @emph{need} to mention the version numbers of libraries which |
| 4958 | 948 are distributed separately from the package which contains this program, |
| 949 you can do so by printing an additional line of version info for each | |
| 950 library you want to mention. Use the same format for these lines as for | |
| 951 the first line. | |
| 952 | |
| 953 Please do not mention all of the libraries that the program uses ``just | |
| 954 for completeness''---that would produce a lot of unhelpful clutter. | |
| 955 Please mention library version numbers only if you find in practice that | |
| 956 they are very important to you in debugging. | |
| 957 | |
| 958 The following line, after the version number line or lines, should be a | |
| 959 copyright notice. If more than one copyright notice is called for, put | |
| 960 each on a separate line. | |
| 961 | |
| 9019 | 962 Next should follow a line stating the license, preferably using one of |
| 963 abbrevations below, and a brief statement that the program is free | |
| 964 software, and that users are free to copy and change it. Also mention | |
| 965 that there is no warranty, to the extent permitted by law. See | |
| 966 recommended wording below. | |
| 4958 | 967 |
| 968 It is ok to finish the output with a list of the major authors of the | |
| 969 program, as a way of giving credit. | |
| 970 | |
| 971 Here's an example of output that follows these rules: | |
| 972 | |
| 973 @smallexample | |
| 9019 | 974 GNU hello 2.3 |
| 975 Copyright (C) 2007 Free Software Foundation, Inc. | |
| 976 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> | |
| 977 This is free software: you are free to change and redistribute it. | |
| 978 There is NO WARRANTY, to the extent permitted by law. | |
| 4958 | 979 @end smallexample |
| 980 | |
| 981 You should adapt this to your program, of course, filling in the proper | |
| 982 year, copyright holder, name of program, and the references to | |
| 983 distribution terms, and changing the rest of the wording as necessary. | |
| 984 | |
| 985 This copyright notice only needs to mention the most recent year in | |
| 986 which changes were made---there's no need to list the years for previous | |
| 987 versions' changes. You don't have to mention the name of the program in | |
| 988 these notices, if that is inconvenient, since it appeared in the first | |
| 6640 | 989 line. (The rules are different for copyright notices in source files; |
| 9019 | 990 @pxref{Copyright Notices,,,maintain,Information for GNU Maintainers}.) |
| 4958 | 991 |
| 992 Translations of the above lines must preserve the validity of the | |
| 993 copyright notices (@pxref{Internationalization}). If the translation's | |
| 994 character set supports it, the @samp{(C)} should be replaced with the | |
| 995 copyright symbol, as follows: | |
| 996 | |
| 6725 | 997 @ifinfo |
| 998 (the official copyright symbol, which is the letter C in a circle); | |
| 999 @end ifinfo | |
| 1000 @ifnotinfo | |
| 4958 | 1001 @copyright{} |
| 6725 | 1002 @end ifnotinfo |
| 4958 | 1003 |
| 1004 Write the word ``Copyright'' exactly like that, in English. Do not | |
| 1005 translate it into another language. International treaties recognize | |
| 1006 the English word ``Copyright''; translations into other languages do not | |
| 1007 have legal significance. | |
| 1008 | |
| 9019 | 1009 Finally, here is the table of our suggested license abbreviations. |
| 1010 Any abbreviation can be followed by @samp{v@var{version}[+]}, meaning | |
| 1011 that particular version, or later versions with the @samp{+}, as shown | |
| 1012 above. | |
| 1013 | |
| 1014 In the case of exceptions for extra permissions with the GPL, we use | |
| 1015 @samp{/} for a separator; the version number can follow the license | |
| 1016 abbreviation as usual, as in the examples below. | |
| 1017 | |
| 1018 @table @asis | |
| 1019 @item GPL | |
| 9823 | 1020 GNU General Public License, @url{http://www.gnu.org/@/licenses/@/gpl.html}. |
| 9019 | 1021 |
| 1022 @item LGPL | |
| 9823 | 1023 GNU Lesser General Public License, @url{http://www.gnu.org/@/licenses/@/lgpl.html}. |
| 9019 | 1024 |
| 1025 @item GPL/Guile | |
| 1026 GNU GPL with the exception for Guile; for example, GPLv3+/Guile means | |
| 1027 the GNU GPL version 3 or later, with the extra exception for Guile. | |
| 1028 | |
| 10037 | 1029 @item GPL/Ada |
| 9019 | 1030 GNU GPL with the exception for Ada. |
| 1031 | |
| 1032 @item Apache | |
| 1033 The Apache Software Foundation license, | |
| 9823 | 1034 @url{http://www.apache.org/@/licenses}. |
| 9019 | 1035 |
| 1036 @item Artistic | |
| 9823 | 1037 The Artistic license used for Perl, @url{http://www.perlfoundation.org/@/legal}. |
| 9019 | 1038 |
| 1039 @item Expat | |
| 9823 | 1040 The Expat license, @url{http://www.jclark.com/@/xml/@/copying.txt}. |
| 9019 | 1041 |
| 1042 @item MPL | |
| 9823 | 1043 The Mozilla Public License, @url{http://www.mozilla.org/@/MPL/}. |
| 9019 | 1044 |
| 1045 @item OBSD | |
| 1046 The original (4-clause) BSD license, incompatible with the GNU GPL | |
| 9823 | 1047 @url{http://www.xfree86.org/@/3.3.6/@/COPYRIGHT2.html#6}. |
| 9019 | 1048 |
| 1049 @item PHP | |
| 9823 | 1050 The license used for PHP, @url{http://www.php.net/@/license/}. |
| 9019 | 1051 |
| 1052 @item public domain | |
| 1053 The non-license that is being in the public domain, | |
| 9823 | 1054 @url{http://www.gnu.org/@/licenses/@/license-list.html#PublicDomain}. |
| 9019 | 1055 |
| 1056 @item Python | |
| 9823 | 1057 The license for Python, @url{http://www.python.org/@/2.0.1/@/license.html}. |
| 9019 | 1058 |
| 1059 @item RBSD | |
| 1060 The revised (3-clause) BSD, compatible with the GNU GPL, | |
| 9823 | 1061 @url{http://www.xfree86.org/@/3.3.6/@/COPYRIGHT2.html#5}. |
| 9019 | 1062 |
| 1063 @item X11 | |
| 1064 The simple non-copyleft license used for most versions of the X Window | |
| 9823 | 1065 system, @url{http://www.xfree86.org/@/3.3.6/@/COPYRIGHT2.html#3}. |
| 9019 | 1066 |
| 1067 @item Zlib | |
| 9823 | 1068 The license for Zlib, @url{http://www.gzip.org/@/zlib/@/zlib_license.html}. |
| 9019 | 1069 |
| 1070 @end table | |
| 1071 | |
| 1072 More information about these licenses and many more are on the GNU | |
| 1073 licensing web pages, | |
| 9823 | 1074 @url{http://www.gnu.org/@/licenses/@/license-list.html}. |
| 9019 | 1075 |
| 1076 | |
| 1077 @node --help | |
| 1078 @subsection @option{--help} | |
| 1079 | |
| 1080 @cindex @samp{--help} output | |
| 1081 | |
| 1082 The standard @code{--help} option should output brief documentation | |
| 1083 for how to invoke the program, on standard output, then exit | |
| 1084 successfully. Other options and arguments should be ignored once this | |
| 1085 is seen, and the program should not perform its normal function. | |
| 4958 | 1086 |
| 1087 @cindex address for bug reports | |
| 1088 @cindex bug reports | |
| 1089 Near the end of the @samp{--help} option's output there should be a line | |
| 1090 that says where to mail bug reports. It should have this format: | |
| 1091 | |
| 1092 @example | |
| 1093 Report bugs to @var{mailing-address}. | |
| 1094 @end example | |
| 9019 | 1095 |
| 4958 | 1096 |
| 1097 @node Option Table | |
| 1098 @section Table of Long Options | |
| 1099 @cindex long option names | |
| 1100 @cindex table of long options | |
| 1101 | |
| 1102 Here is a table of long options used by GNU programs. It is surely | |
| 1103 incomplete, but we aim to list all the options that a new program might | |
| 1104 want to be compatible with. If you use names not already in the table, | |
| 1105 please send @email{bug-standards@@gnu.org} a list of them, with their | |
| 1106 meanings, so we can update the table. | |
| 1107 | |
| 1108 @c Please leave newlines between items in this table; it's much easier | |
| 1109 @c to update when it isn't completely squashed together and unreadable. | |
| 1110 @c When there is more than one short option for a long option name, put | |
| 1111 @c a semicolon between the lists of the programs that use them, not a | |
| 1112 @c period. --friedman | |
| 1113 | |
| 1114 @table @samp | |
| 1115 @item after-date | |
| 1116 @samp{-N} in @code{tar}. | |
| 1117 | |
| 1118 @item all | |
| 1119 @samp{-a} in @code{du}, @code{ls}, @code{nm}, @code{stty}, @code{uname}, | |
| 1120 and @code{unexpand}. | |
| 1121 | |
| 1122 @item all-text | |
| 1123 @samp{-a} in @code{diff}. | |
| 1124 | |
| 1125 @item almost-all | |
| 1126 @samp{-A} in @code{ls}. | |
| 1127 | |
| 1128 @item append | |
| 1129 @samp{-a} in @code{etags}, @code{tee}, @code{time}; | |
| 1130 @samp{-r} in @code{tar}. | |
| 1131 | |
| 1132 @item archive | |
| 1133 @samp{-a} in @code{cp}. | |
| 1134 | |
| 1135 @item archive-name | |
| 1136 @samp{-n} in @code{shar}. | |
| 1137 | |
| 1138 @item arglength | |
| 1139 @samp{-l} in @code{m4}. | |
| 1140 | |
| 1141 @item ascii | |
| 1142 @samp{-a} in @code{diff}. | |
| 1143 | |
| 1144 @item assign | |
| 1145 @samp{-v} in @code{gawk}. | |
| 1146 | |
| 1147 @item assume-new | |
| 10199 | 1148 @samp{-W} in @code{make}. |
| 4958 | 1149 |
| 1150 @item assume-old | |
| 10199 | 1151 @samp{-o} in @code{make}. |
| 4958 | 1152 |
| 1153 @item auto-check | |
| 1154 @samp{-a} in @code{recode}. | |
| 1155 | |
| 1156 @item auto-pager | |
| 1157 @samp{-a} in @code{wdiff}. | |
| 1158 | |
| 1159 @item auto-reference | |
| 1160 @samp{-A} in @code{ptx}. | |
| 1161 | |
| 1162 @item avoid-wraps | |
| 1163 @samp{-n} in @code{wdiff}. | |
| 1164 | |
| 1165 @item background | |
| 1166 For server programs, run in the background. | |
| 1167 | |
| 1168 @item backward-search | |
| 1169 @samp{-B} in @code{ctags}. | |
| 1170 | |
| 1171 @item basename | |
| 1172 @samp{-f} in @code{shar}. | |
| 1173 | |
| 1174 @item batch | |
| 1175 Used in GDB. | |
| 1176 | |
| 1177 @item baud | |
| 1178 Used in GDB. | |
| 1179 | |
| 1180 @item before | |
| 1181 @samp{-b} in @code{tac}. | |
| 1182 | |
| 1183 @item binary | |
| 1184 @samp{-b} in @code{cpio} and @code{diff}. | |
| 1185 | |
| 1186 @item bits-per-code | |
| 1187 @samp{-b} in @code{shar}. | |
| 1188 | |
| 1189 @item block-size | |
| 1190 Used in @code{cpio} and @code{tar}. | |
| 1191 | |
| 1192 @item blocks | |
| 1193 @samp{-b} in @code{head} and @code{tail}. | |
| 1194 | |
| 1195 @item break-file | |
| 1196 @samp{-b} in @code{ptx}. | |
| 1197 | |
| 1198 @item brief | |
| 1199 Used in various programs to make output shorter. | |
| 1200 | |
| 1201 @item bytes | |
| 1202 @samp{-c} in @code{head}, @code{split}, and @code{tail}. | |
| 1203 | |
| 1204 @item c@t{++} | |
| 1205 @samp{-C} in @code{etags}. | |
| 1206 | |
| 1207 @item catenate | |
| 1208 @samp{-A} in @code{tar}. | |
| 1209 | |
| 1210 @item cd | |
| 1211 Used in various programs to specify the directory to use. | |
| 1212 | |
| 1213 @item changes | |
| 1214 @samp{-c} in @code{chgrp} and @code{chown}. | |
| 1215 | |
| 1216 @item classify | |
| 1217 @samp{-F} in @code{ls}. | |
| 1218 | |
| 1219 @item colons | |
| 1220 @samp{-c} in @code{recode}. | |
| 1221 | |
| 1222 @item command | |
| 1223 @samp{-c} in @code{su}; | |
| 1224 @samp{-x} in GDB. | |
| 1225 | |
| 1226 @item compare | |
| 1227 @samp{-d} in @code{tar}. | |
| 1228 | |
| 1229 @item compat | |
| 1230 Used in @code{gawk}. | |
| 1231 | |
| 1232 @item compress | |
| 1233 @samp{-Z} in @code{tar} and @code{shar}. | |
| 1234 | |
| 1235 @item concatenate | |
| 1236 @samp{-A} in @code{tar}. | |
| 1237 | |
| 1238 @item confirmation | |
| 1239 @samp{-w} in @code{tar}. | |
| 1240 | |
| 1241 @item context | |
| 1242 Used in @code{diff}. | |
| 1243 | |
| 1244 @item copyleft | |
| 1245 @samp{-W copyleft} in @code{gawk}. | |
| 1246 | |
| 1247 @item copyright | |
| 1248 @samp{-C} in @code{ptx}, @code{recode}, and @code{wdiff}; | |
| 1249 @samp{-W copyright} in @code{gawk}. | |
| 1250 | |
| 1251 @item core | |
| 1252 Used in GDB. | |
| 1253 | |
| 1254 @item count | |
| 1255 @samp{-q} in @code{who}. | |
| 1256 | |
| 1257 @item count-links | |
| 1258 @samp{-l} in @code{du}. | |
| 1259 | |
| 1260 @item create | |
| 1261 Used in @code{tar} and @code{cpio}. | |
| 1262 | |
| 1263 @item cut-mark | |
| 1264 @samp{-c} in @code{shar}. | |
| 1265 | |
| 1266 @item cxref | |
| 1267 @samp{-x} in @code{ctags}. | |
| 1268 | |
| 1269 @item date | |
| 1270 @samp{-d} in @code{touch}. | |
| 1271 | |
| 1272 @item debug | |
| 10199 | 1273 @samp{-d} in @code{make} and @code{m4}; |
| 4958 | 1274 @samp{-t} in Bison. |
| 1275 | |
| 1276 @item define | |
| 1277 @samp{-D} in @code{m4}. | |
| 1278 | |
| 1279 @item defines | |
| 1280 @samp{-d} in Bison and @code{ctags}. | |
| 1281 | |
| 1282 @item delete | |
| 1283 @samp{-D} in @code{tar}. | |
| 1284 | |
| 1285 @item dereference | |
| 1286 @samp{-L} in @code{chgrp}, @code{chown}, @code{cpio}, @code{du}, | |
| 1287 @code{ls}, and @code{tar}. | |
| 1288 | |
| 1289 @item dereference-args | |
| 1290 @samp{-D} in @code{du}. | |
| 1291 | |
| 1292 @item device | |
| 1293 Specify an I/O device (special file name). | |
| 1294 | |
| 1295 @item diacritics | |
| 1296 @samp{-d} in @code{recode}. | |
| 1297 | |
| 1298 @item dictionary-order | |
| 1299 @samp{-d} in @code{look}. | |
| 1300 | |
| 1301 @item diff | |
| 1302 @samp{-d} in @code{tar}. | |
| 1303 | |
| 1304 @item digits | |
| 1305 @samp{-n} in @code{csplit}. | |
| 1306 | |
| 1307 @item directory | |
| 1308 Specify the directory to use, in various programs. In @code{ls}, it | |
| 1309 means to show directories themselves rather than their contents. In | |
| 1310 @code{rm} and @code{ln}, it means to not treat links to directories | |
| 1311 specially. | |
| 1312 | |
| 1313 @item discard-all | |
| 1314 @samp{-x} in @code{strip}. | |
| 1315 | |
| 1316 @item discard-locals | |
| 1317 @samp{-X} in @code{strip}. | |
| 1318 | |
| 1319 @item dry-run | |
| 10199 | 1320 @samp{-n} in @code{make}. |
| 4958 | 1321 |
| 1322 @item ed | |
| 1323 @samp{-e} in @code{diff}. | |
| 1324 | |
| 1325 @item elide-empty-files | |
| 1326 @samp{-z} in @code{csplit}. | |
| 1327 | |
| 1328 @item end-delete | |
| 1329 @samp{-x} in @code{wdiff}. | |
| 1330 | |
| 1331 @item end-insert | |
| 1332 @samp{-z} in @code{wdiff}. | |
| 1333 | |
| 1334 @item entire-new-file | |
| 1335 @samp{-N} in @code{diff}. | |
| 1336 | |
| 1337 @item environment-overrides | |
| 10199 | 1338 @samp{-e} in @code{make}. |
| 4958 | 1339 |
| 1340 @item eof | |
| 1341 @samp{-e} in @code{xargs}. | |
| 1342 | |
| 1343 @item epoch | |
| 1344 Used in GDB. | |
| 1345 | |
| 1346 @item error-limit | |
| 1347 Used in @code{makeinfo}. | |
| 1348 | |
| 1349 @item error-output | |
| 1350 @samp{-o} in @code{m4}. | |
| 1351 | |
| 1352 @item escape | |
| 1353 @samp{-b} in @code{ls}. | |
| 1354 | |
| 1355 @item exclude-from | |
| 1356 @samp{-X} in @code{tar}. | |
| 1357 | |
| 1358 @item exec | |
| 1359 Used in GDB. | |
| 1360 | |
| 1361 @item exit | |
| 1362 @samp{-x} in @code{xargs}. | |
| 1363 | |
| 1364 @item exit-0 | |
| 1365 @samp{-e} in @code{unshar}. | |
| 1366 | |
| 1367 @item expand-tabs | |
| 1368 @samp{-t} in @code{diff}. | |
| 1369 | |
| 1370 @item expression | |
| 1371 @samp{-e} in @code{sed}. | |
| 1372 | |
| 1373 @item extern-only | |
| 1374 @samp{-g} in @code{nm}. | |
| 1375 | |
| 1376 @item extract | |
| 1377 @samp{-i} in @code{cpio}; | |
| 1378 @samp{-x} in @code{tar}. | |
| 1379 | |
| 1380 @item faces | |
| 1381 @samp{-f} in @code{finger}. | |
| 1382 | |
| 1383 @item fast | |
| 1384 @samp{-f} in @code{su}. | |
| 1385 | |
| 1386 @item fatal-warnings | |
| 1387 @samp{-E} in @code{m4}. | |
| 1388 | |
| 1389 @item file | |
| 10199 | 1390 @samp{-f} in @code{gawk}, @code{info}, @code{make}, @code{mt}, |
| 1391 @code{sed}, and @code{tar}. | |
| 4958 | 1392 |
| 1393 @item field-separator | |
| 1394 @samp{-F} in @code{gawk}. | |
| 1395 | |
| 1396 @item file-prefix | |
| 1397 @samp{-b} in Bison. | |
| 1398 | |
| 1399 @item file-type | |
| 1400 @samp{-F} in @code{ls}. | |
| 1401 | |
| 1402 @item files-from | |
| 1403 @samp{-T} in @code{tar}. | |
| 1404 | |
| 1405 @item fill-column | |
| 1406 Used in @code{makeinfo}. | |
| 1407 | |
| 1408 @item flag-truncation | |
| 1409 @samp{-F} in @code{ptx}. | |
| 1410 | |
| 1411 @item fixed-output-files | |
| 1412 @samp{-y} in Bison. | |
| 1413 | |
| 1414 @item follow | |
| 1415 @samp{-f} in @code{tail}. | |
| 1416 | |
| 1417 @item footnote-style | |
| 1418 Used in @code{makeinfo}. | |
| 1419 | |
| 1420 @item force | |
| 1421 @samp{-f} in @code{cp}, @code{ln}, @code{mv}, and @code{rm}. | |
| 1422 | |
| 1423 @item force-prefix | |
| 1424 @samp{-F} in @code{shar}. | |
| 1425 | |
| 1426 @item foreground | |
| 1427 For server programs, run in the foreground; | |
| 1428 in other words, don't do anything special to run the server | |
| 1429 in the background. | |
| 1430 | |
| 1431 @item format | |
| 1432 Used in @code{ls}, @code{time}, and @code{ptx}. | |
| 1433 | |
| 1434 @item freeze-state | |
| 1435 @samp{-F} in @code{m4}. | |
| 1436 | |
| 1437 @item fullname | |
| 1438 Used in GDB. | |
| 1439 | |
| 1440 @item gap-size | |
| 1441 @samp{-g} in @code{ptx}. | |
| 1442 | |
| 1443 @item get | |
| 1444 @samp{-x} in @code{tar}. | |
| 1445 | |
| 1446 @item graphic | |
| 1447 @samp{-i} in @code{ul}. | |
| 1448 | |
| 1449 @item graphics | |
| 1450 @samp{-g} in @code{recode}. | |
| 1451 | |
| 1452 @item group | |
| 1453 @samp{-g} in @code{install}. | |
| 1454 | |
| 1455 @item gzip | |
| 1456 @samp{-z} in @code{tar} and @code{shar}. | |
| 1457 | |
| 1458 @item hashsize | |
| 1459 @samp{-H} in @code{m4}. | |
| 1460 | |
| 1461 @item header | |
| 1462 @samp{-h} in @code{objdump} and @code{recode} | |
| 1463 | |
| 1464 @item heading | |
| 1465 @samp{-H} in @code{who}. | |
| 1466 | |
| 1467 @item help | |
| 1468 Used to ask for brief usage information. | |
| 1469 | |
| 1470 @item here-delimiter | |
| 1471 @samp{-d} in @code{shar}. | |
| 1472 | |
| 1473 @item hide-control-chars | |
| 1474 @samp{-q} in @code{ls}. | |
| 1475 | |
| 1476 @item html | |
| 1477 In @code{makeinfo}, output HTML. | |
| 1478 | |
| 1479 @item idle | |
| 1480 @samp{-u} in @code{who}. | |
| 1481 | |
| 1482 @item ifdef | |
| 1483 @samp{-D} in @code{diff}. | |
| 1484 | |
| 1485 @item ignore | |
| 1486 @samp{-I} in @code{ls}; | |
| 1487 @samp{-x} in @code{recode}. | |
| 1488 | |
| 1489 @item ignore-all-space | |
| 1490 @samp{-w} in @code{diff}. | |
| 1491 | |
| 1492 @item ignore-backups | |
| 1493 @samp{-B} in @code{ls}. | |
| 1494 | |
| 1495 @item ignore-blank-lines | |
| 1496 @samp{-B} in @code{diff}. | |
| 1497 | |
| 1498 @item ignore-case | |
| 1499 @samp{-f} in @code{look} and @code{ptx}; | |
| 1500 @samp{-i} in @code{diff} and @code{wdiff}. | |
| 1501 | |
| 1502 @item ignore-errors | |
| 10199 | 1503 @samp{-i} in @code{make}. |
| 4958 | 1504 |
| 1505 @item ignore-file | |
| 1506 @samp{-i} in @code{ptx}. | |
| 1507 | |
| 1508 @item ignore-indentation | |
| 1509 @samp{-I} in @code{etags}. | |
| 1510 | |
| 1511 @item ignore-init-file | |
| 1512 @samp{-f} in Oleo. | |
| 1513 | |
| 1514 @item ignore-interrupts | |
| 1515 @samp{-i} in @code{tee}. | |
| 1516 | |
| 1517 @item ignore-matching-lines | |
| 1518 @samp{-I} in @code{diff}. | |
| 1519 | |
| 1520 @item ignore-space-change | |
| 1521 @samp{-b} in @code{diff}. | |
| 1522 | |
| 1523 @item ignore-zeros | |
| 1524 @samp{-i} in @code{tar}. | |
| 1525 | |
| 1526 @item include | |
| 1527 @samp{-i} in @code{etags}; | |
| 1528 @samp{-I} in @code{m4}. | |
| 1529 | |
| 1530 @item include-dir | |
| 10199 | 1531 @samp{-I} in @code{make}. |
| 4958 | 1532 |
| 1533 @item incremental | |
| 1534 @samp{-G} in @code{tar}. | |
| 1535 | |
| 1536 @item info | |
| 1537 @samp{-i}, @samp{-l}, and @samp{-m} in Finger. | |
| 1538 | |
| 1539 @item init-file | |
| 1540 In some programs, specify the name of the file to read as the user's | |
| 1541 init file. | |
| 1542 | |
| 1543 @item initial | |
| 1544 @samp{-i} in @code{expand}. | |
| 1545 | |
| 1546 @item initial-tab | |
| 1547 @samp{-T} in @code{diff}. | |
| 1548 | |
| 1549 @item inode | |
| 1550 @samp{-i} in @code{ls}. | |
| 1551 | |
| 1552 @item interactive | |
| 1553 @samp{-i} in @code{cp}, @code{ln}, @code{mv}, @code{rm}; | |
| 1554 @samp{-e} in @code{m4}; | |
| 1555 @samp{-p} in @code{xargs}; | |
| 1556 @samp{-w} in @code{tar}. | |
| 1557 | |
| 1558 @item intermix-type | |
| 1559 @samp{-p} in @code{shar}. | |
| 1560 | |
| 1561 @item iso-8601 | |
| 1562 Used in @code{date} | |
| 1563 | |
| 1564 @item jobs | |
| 10199 | 1565 @samp{-j} in @code{make}. |
| 4958 | 1566 |
| 1567 @item just-print | |
| 10199 | 1568 @samp{-n} in @code{make}. |
| 4958 | 1569 |
| 1570 @item keep-going | |
| 10199 | 1571 @samp{-k} in @code{make}. |
| 4958 | 1572 |
| 1573 @item keep-files | |
| 1574 @samp{-k} in @code{csplit}. | |
| 1575 | |
| 1576 @item kilobytes | |
| 1577 @samp{-k} in @code{du} and @code{ls}. | |
| 1578 | |
| 1579 @item language | |
| 1580 @samp{-l} in @code{etags}. | |
| 1581 | |
| 1582 @item less-mode | |
| 1583 @samp{-l} in @code{wdiff}. | |
| 1584 | |
| 1585 @item level-for-gzip | |
| 1586 @samp{-g} in @code{shar}. | |
| 1587 | |
| 1588 @item line-bytes | |
| 1589 @samp{-C} in @code{split}. | |
| 1590 | |
| 1591 @item lines | |
| 1592 Used in @code{split}, @code{head}, and @code{tail}. | |
| 1593 | |
| 1594 @item link | |
| 1595 @samp{-l} in @code{cpio}. | |
| 1596 | |
| 1597 @item lint | |
| 1598 @itemx lint-old | |
| 1599 Used in @code{gawk}. | |
| 1600 | |
| 1601 @item list | |
| 1602 @samp{-t} in @code{cpio}; | |
| 1603 @samp{-l} in @code{recode}. | |
| 1604 | |
| 1605 @item list | |
| 1606 @samp{-t} in @code{tar}. | |
| 1607 | |
| 1608 @item literal | |
| 1609 @samp{-N} in @code{ls}. | |
| 1610 | |
| 1611 @item load-average | |
| 10199 | 1612 @samp{-l} in @code{make}. |
| 4958 | 1613 |
| 1614 @item login | |
| 1615 Used in @code{su}. | |
| 1616 | |
| 1617 @item machine | |
| 5560 | 1618 Used in @code{uname}. |
| 4958 | 1619 |
| 1620 @item macro-name | |
| 1621 @samp{-M} in @code{ptx}. | |
| 1622 | |
| 1623 @item mail | |
| 1624 @samp{-m} in @code{hello} and @code{uname}. | |
| 1625 | |
| 1626 @item make-directories | |
| 1627 @samp{-d} in @code{cpio}. | |
| 1628 | |
| 1629 @item makefile | |
| 10199 | 1630 @samp{-f} in @code{make}. |
| 4958 | 1631 |
| 1632 @item mapped | |
| 1633 Used in GDB. | |
| 1634 | |
| 1635 @item max-args | |
| 1636 @samp{-n} in @code{xargs}. | |
| 1637 | |
| 1638 @item max-chars | |
| 1639 @samp{-n} in @code{xargs}. | |
| 1640 | |
| 1641 @item max-lines | |
| 1642 @samp{-l} in @code{xargs}. | |
| 1643 | |
| 1644 @item max-load | |
| 10199 | 1645 @samp{-l} in @code{make}. |
| 4958 | 1646 |
| 1647 @item max-procs | |
| 1648 @samp{-P} in @code{xargs}. | |
| 1649 | |
| 1650 @item mesg | |
| 1651 @samp{-T} in @code{who}. | |
| 1652 | |
| 1653 @item message | |
| 1654 @samp{-T} in @code{who}. | |
| 1655 | |
| 1656 @item minimal | |
| 1657 @samp{-d} in @code{diff}. | |
| 1658 | |
| 1659 @item mixed-uuencode | |
| 1660 @samp{-M} in @code{shar}. | |
| 1661 | |
| 1662 @item mode | |
| 1663 @samp{-m} in @code{install}, @code{mkdir}, and @code{mkfifo}. | |
| 1664 | |
| 1665 @item modification-time | |
| 1666 @samp{-m} in @code{tar}. | |
| 1667 | |
| 1668 @item multi-volume | |
| 1669 @samp{-M} in @code{tar}. | |
| 1670 | |
| 1671 @item name-prefix | |
| 1672 @samp{-a} in Bison. | |
| 1673 | |
| 1674 @item nesting-limit | |
| 1675 @samp{-L} in @code{m4}. | |
| 1676 | |
| 1677 @item net-headers | |
| 1678 @samp{-a} in @code{shar}. | |
| 1679 | |
| 1680 @item new-file | |
| 10199 | 1681 @samp{-W} in @code{make}. |
| 4958 | 1682 |
| 1683 @item no-builtin-rules | |
| 10199 | 1684 @samp{-r} in @code{make}. |
| 4958 | 1685 |
| 1686 @item no-character-count | |
| 1687 @samp{-w} in @code{shar}. | |
| 1688 | |
| 1689 @item no-check-existing | |
| 1690 @samp{-x} in @code{shar}. | |
| 1691 | |
| 1692 @item no-common | |
| 1693 @samp{-3} in @code{wdiff}. | |
| 1694 | |
| 1695 @item no-create | |
| 1696 @samp{-c} in @code{touch}. | |
| 1697 | |
| 1698 @item no-defines | |
| 1699 @samp{-D} in @code{etags}. | |
| 1700 | |
| 1701 @item no-deleted | |
| 1702 @samp{-1} in @code{wdiff}. | |
| 1703 | |
| 1704 @item no-dereference | |
| 1705 @samp{-d} in @code{cp}. | |
| 1706 | |
| 1707 @item no-inserted | |
| 1708 @samp{-2} in @code{wdiff}. | |
| 1709 | |
| 1710 @item no-keep-going | |
| 10199 | 1711 @samp{-S} in @code{make}. |
| 4958 | 1712 |
| 1713 @item no-lines | |
| 1714 @samp{-l} in Bison. | |
| 1715 | |
| 1716 @item no-piping | |
| 1717 @samp{-P} in @code{shar}. | |
| 1718 | |
| 1719 @item no-prof | |
| 1720 @samp{-e} in @code{gprof}. | |
| 1721 | |
| 1722 @item no-regex | |
| 1723 @samp{-R} in @code{etags}. | |
| 1724 | |
| 1725 @item no-sort | |
| 1726 @samp{-p} in @code{nm}. | |
| 1727 | |
| 1728 @item no-splash | |
| 1729 Don't print a startup splash screen. | |
| 1730 | |
| 1731 @item no-split | |
| 1732 Used in @code{makeinfo}. | |
| 1733 | |
| 1734 @item no-static | |
| 1735 @samp{-a} in @code{gprof}. | |
| 1736 | |
| 1737 @item no-time | |
| 1738 @samp{-E} in @code{gprof}. | |
| 1739 | |
| 1740 @item no-timestamp | |
| 1741 @samp{-m} in @code{shar}. | |
| 1742 | |
| 1743 @item no-validate | |
| 1744 Used in @code{makeinfo}. | |
| 1745 | |
| 1746 @item no-wait | |
| 1747 Used in @code{emacsclient}. | |
| 1748 | |
| 1749 @item no-warn | |
| 1750 Used in various programs to inhibit warnings. | |
| 1751 | |
| 1752 @item node | |
| 1753 @samp{-n} in @code{info}. | |
| 1754 | |
| 1755 @item nodename | |
| 1756 @samp{-n} in @code{uname}. | |
| 1757 | |
| 1758 @item nonmatching | |
| 1759 @samp{-f} in @code{cpio}. | |
| 1760 | |
| 1761 @item nstuff | |
| 1762 @samp{-n} in @code{objdump}. | |
| 1763 | |
| 1764 @item null | |
| 1765 @samp{-0} in @code{xargs}. | |
| 1766 | |
| 1767 @item number | |
| 1768 @samp{-n} in @code{cat}. | |
| 1769 | |
| 1770 @item number-nonblank | |
| 1771 @samp{-b} in @code{cat}. | |
| 1772 | |
| 1773 @item numeric-sort | |
| 1774 @samp{-n} in @code{nm}. | |
| 1775 | |
| 1776 @item numeric-uid-gid | |
| 1777 @samp{-n} in @code{cpio} and @code{ls}. | |
| 1778 | |
| 1779 @item nx | |
| 1780 Used in GDB. | |
| 1781 | |
| 1782 @item old-archive | |
| 1783 @samp{-o} in @code{tar}. | |
| 1784 | |
| 1785 @item old-file | |
| 10199 | 1786 @samp{-o} in @code{make}. |
| 4958 | 1787 |
| 1788 @item one-file-system | |
| 1789 @samp{-l} in @code{tar}, @code{cp}, and @code{du}. | |
| 1790 | |
| 1791 @item only-file | |
| 1792 @samp{-o} in @code{ptx}. | |
| 1793 | |
| 1794 @item only-prof | |
| 1795 @samp{-f} in @code{gprof}. | |
| 1796 | |
| 1797 @item only-time | |
| 1798 @samp{-F} in @code{gprof}. | |
| 1799 | |
| 1800 @item options | |
| 1801 @samp{-o} in @code{getopt}, @code{fdlist}, @code{fdmount}, | |
| 1802 @code{fdmountd}, and @code{fdumount}. | |
| 1803 | |
| 1804 @item output | |
| 1805 In various programs, specify the output file name. | |
| 1806 | |
| 1807 @item output-prefix | |
| 1808 @samp{-o} in @code{shar}. | |
| 1809 | |
| 1810 @item override | |
| 1811 @samp{-o} in @code{rm}. | |
| 1812 | |
| 1813 @item overwrite | |
| 1814 @samp{-c} in @code{unshar}. | |
| 1815 | |
| 1816 @item owner | |
| 1817 @samp{-o} in @code{install}. | |
| 1818 | |
| 1819 @item paginate | |
| 1820 @samp{-l} in @code{diff}. | |
| 1821 | |
| 1822 @item paragraph-indent | |
| 1823 Used in @code{makeinfo}. | |
| 1824 | |
| 1825 @item parents | |
| 1826 @samp{-p} in @code{mkdir} and @code{rmdir}. | |
| 1827 | |
| 1828 @item pass-all | |
| 1829 @samp{-p} in @code{ul}. | |
| 1830 | |
| 1831 @item pass-through | |
| 1832 @samp{-p} in @code{cpio}. | |
| 1833 | |
| 1834 @item port | |
| 1835 @samp{-P} in @code{finger}. | |
| 1836 | |
| 1837 @item portability | |
| 1838 @samp{-c} in @code{cpio} and @code{tar}. | |
| 1839 | |
| 1840 @item posix | |
| 1841 Used in @code{gawk}. | |
| 1842 | |
| 1843 @item prefix-builtins | |
| 1844 @samp{-P} in @code{m4}. | |
| 1845 | |
| 1846 @item prefix | |
| 1847 @samp{-f} in @code{csplit}. | |
| 1848 | |
| 1849 @item preserve | |
| 1850 Used in @code{tar} and @code{cp}. | |
| 1851 | |
| 1852 @item preserve-environment | |
| 1853 @samp{-p} in @code{su}. | |
| 1854 | |
| 1855 @item preserve-modification-time | |
| 1856 @samp{-m} in @code{cpio}. | |
| 1857 | |
| 1858 @item preserve-order | |
| 1859 @samp{-s} in @code{tar}. | |
| 1860 | |
| 1861 @item preserve-permissions | |
| 1862 @samp{-p} in @code{tar}. | |
| 1863 | |
| 1864 @item print | |
| 1865 @samp{-l} in @code{diff}. | |
| 1866 | |
| 1867 @item print-chars | |
| 1868 @samp{-L} in @code{cmp}. | |
| 1869 | |
| 1870 @item print-data-base | |
| 10199 | 1871 @samp{-p} in @code{make}. |
| 4958 | 1872 |
| 1873 @item print-directory | |
| 10199 | 1874 @samp{-w} in @code{make}. |
| 4958 | 1875 |
| 1876 @item print-file-name | |
| 1877 @samp{-o} in @code{nm}. | |
| 1878 | |
| 1879 @item print-symdefs | |
| 1880 @samp{-s} in @code{nm}. | |
| 1881 | |
| 1882 @item printer | |
| 1883 @samp{-p} in @code{wdiff}. | |
| 1884 | |
| 1885 @item prompt | |
| 1886 @samp{-p} in @code{ed}. | |
| 1887 | |
| 1888 @item proxy | |
| 1889 Specify an HTTP proxy. | |
| 1890 | |
| 1891 @item query-user | |
| 1892 @samp{-X} in @code{shar}. | |
| 1893 | |
| 1894 @item question | |
| 10199 | 1895 @samp{-q} in @code{make}. |
| 4958 | 1896 |
| 1897 @item quiet | |
| 1898 Used in many programs to inhibit the usual output. Every | |
| 1899 program accepting @samp{--quiet} should accept @samp{--silent} as a | |
| 1900 synonym. | |
| 1901 | |
| 1902 @item quiet-unshar | |
| 1903 @samp{-Q} in @code{shar} | |
| 1904 | |
| 1905 @item quote-name | |
| 1906 @samp{-Q} in @code{ls}. | |
| 1907 | |
| 1908 @item rcs | |
| 1909 @samp{-n} in @code{diff}. | |
| 1910 | |
| 1911 @item re-interval | |
| 1912 Used in @code{gawk}. | |
| 1913 | |
| 1914 @item read-full-blocks | |
| 1915 @samp{-B} in @code{tar}. | |
| 1916 | |
| 1917 @item readnow | |
| 1918 Used in GDB. | |
| 1919 | |
| 1920 @item recon | |
| 10199 | 1921 @samp{-n} in @code{make}. |
| 4958 | 1922 |
| 1923 @item record-number | |
| 1924 @samp{-R} in @code{tar}. | |
| 1925 | |
| 1926 @item recursive | |
| 1927 Used in @code{chgrp}, @code{chown}, @code{cp}, @code{ls}, @code{diff}, | |
| 1928 and @code{rm}. | |
| 1929 | |
| 10199 | 1930 @item reference |
| 1931 @samp{-r} in @code{touch}. | |
| 4958 | 1932 |
| 1933 @item references | |
| 1934 @samp{-r} in @code{ptx}. | |
| 1935 | |
| 1936 @item regex | |
| 1937 @samp{-r} in @code{tac} and @code{etags}. | |
| 1938 | |
| 1939 @item release | |
| 1940 @samp{-r} in @code{uname}. | |
| 1941 | |
| 1942 @item reload-state | |
| 1943 @samp{-R} in @code{m4}. | |
| 1944 | |
| 1945 @item relocation | |
| 1946 @samp{-r} in @code{objdump}. | |
| 1947 | |
| 1948 @item rename | |
| 1949 @samp{-r} in @code{cpio}. | |
| 1950 | |
| 1951 @item replace | |
| 1952 @samp{-i} in @code{xargs}. | |
| 1953 | |
| 1954 @item report-identical-files | |
| 1955 @samp{-s} in @code{diff}. | |
| 1956 | |
| 1957 @item reset-access-time | |
| 1958 @samp{-a} in @code{cpio}. | |
| 1959 | |
| 1960 @item reverse | |
| 1961 @samp{-r} in @code{ls} and @code{nm}. | |
| 1962 | |
| 1963 @item reversed-ed | |
| 1964 @samp{-f} in @code{diff}. | |
| 1965 | |
| 1966 @item right-side-defs | |
| 1967 @samp{-R} in @code{ptx}. | |
| 1968 | |
| 1969 @item same-order | |
| 1970 @samp{-s} in @code{tar}. | |
| 1971 | |
| 1972 @item same-permissions | |
| 1973 @samp{-p} in @code{tar}. | |
| 1974 | |
| 1975 @item save | |
| 1976 @samp{-g} in @code{stty}. | |
| 1977 | |
| 1978 @item se | |
| 1979 Used in GDB. | |
| 1980 | |
| 1981 @item sentence-regexp | |
| 1982 @samp{-S} in @code{ptx}. | |
| 1983 | |
| 1984 @item separate-dirs | |
| 1985 @samp{-S} in @code{du}. | |
| 1986 | |
| 1987 @item separator | |
| 1988 @samp{-s} in @code{tac}. | |
| 1989 | |
| 1990 @item sequence | |
| 1991 Used by @code{recode} to chose files or pipes for sequencing passes. | |
| 1992 | |
| 1993 @item shell | |
| 1994 @samp{-s} in @code{su}. | |
| 1995 | |
| 1996 @item show-all | |
| 1997 @samp{-A} in @code{cat}. | |
| 1998 | |
| 1999 @item show-c-function | |
| 2000 @samp{-p} in @code{diff}. | |
| 2001 | |
| 2002 @item show-ends | |
| 2003 @samp{-E} in @code{cat}. | |
| 2004 | |
| 2005 @item show-function-line | |
| 2006 @samp{-F} in @code{diff}. | |
| 2007 | |
| 2008 @item show-tabs | |
| 2009 @samp{-T} in @code{cat}. | |
| 2010 | |
| 2011 @item silent | |
| 2012 Used in many programs to inhibit the usual output. | |
| 2013 Every program accepting | |
| 2014 @samp{--silent} should accept @samp{--quiet} as a synonym. | |
| 2015 | |
| 2016 @item size | |
| 2017 @samp{-s} in @code{ls}. | |
| 2018 | |
| 2019 @item socket | |
| 2020 Specify a file descriptor for a network server to use for its socket, | |
| 2021 instead of opening and binding a new socket. This provides a way to | |
| 6946 | 2022 run, in a non-privileged process, a server that normally needs a |
| 4958 | 2023 reserved port number. |
| 2024 | |
| 2025 @item sort | |
| 2026 Used in @code{ls}. | |
| 2027 | |
| 2028 @item source | |
| 2029 @samp{-W source} in @code{gawk}. | |
| 2030 | |
| 2031 @item sparse | |
| 2032 @samp{-S} in @code{tar}. | |
| 2033 | |
| 2034 @item speed-large-files | |
| 2035 @samp{-H} in @code{diff}. | |
| 2036 | |
| 2037 @item split-at | |
| 2038 @samp{-E} in @code{unshar}. | |
| 2039 | |
| 2040 @item split-size-limit | |
| 2041 @samp{-L} in @code{shar}. | |
| 2042 | |
| 2043 @item squeeze-blank | |
| 2044 @samp{-s} in @code{cat}. | |
| 2045 | |
| 2046 @item start-delete | |
| 2047 @samp{-w} in @code{wdiff}. | |
| 2048 | |
| 2049 @item start-insert | |
| 2050 @samp{-y} in @code{wdiff}. | |
| 2051 | |
| 2052 @item starting-file | |
| 2053 Used in @code{tar} and @code{diff} to specify which file within | |
| 2054 a directory to start processing with. | |
| 2055 | |
| 2056 @item statistics | |
| 2057 @samp{-s} in @code{wdiff}. | |
| 2058 | |
| 2059 @item stdin-file-list | |
| 2060 @samp{-S} in @code{shar}. | |
| 2061 | |
| 2062 @item stop | |
| 10199 | 2063 @samp{-S} in @code{make}. |
| 4958 | 2064 |
| 2065 @item strict | |
| 2066 @samp{-s} in @code{recode}. | |
| 2067 | |
| 2068 @item strip | |
| 2069 @samp{-s} in @code{install}. | |
| 2070 | |
| 2071 @item strip-all | |
| 2072 @samp{-s} in @code{strip}. | |
| 2073 | |
| 2074 @item strip-debug | |
| 2075 @samp{-S} in @code{strip}. | |
| 2076 | |
| 2077 @item submitter | |
| 2078 @samp{-s} in @code{shar}. | |
| 2079 | |
| 2080 @item suffix | |
| 2081 @samp{-S} in @code{cp}, @code{ln}, @code{mv}. | |
| 2082 | |
| 2083 @item suffix-format | |
| 2084 @samp{-b} in @code{csplit}. | |
| 2085 | |
| 2086 @item sum | |
| 2087 @samp{-s} in @code{gprof}. | |
| 2088 | |
| 2089 @item summarize | |
| 2090 @samp{-s} in @code{du}. | |
| 2091 | |
| 2092 @item symbolic | |
| 2093 @samp{-s} in @code{ln}. | |
| 2094 | |
| 2095 @item symbols | |
| 2096 Used in GDB and @code{objdump}. | |
| 2097 | |
| 2098 @item synclines | |
| 2099 @samp{-s} in @code{m4}. | |
| 2100 | |
| 2101 @item sysname | |
| 2102 @samp{-s} in @code{uname}. | |
| 2103 | |
| 2104 @item tabs | |
| 2105 @samp{-t} in @code{expand} and @code{unexpand}. | |
| 2106 | |
| 2107 @item tabsize | |
| 2108 @samp{-T} in @code{ls}. | |
| 2109 | |
| 2110 @item terminal | |
| 2111 @samp{-T} in @code{tput} and @code{ul}. | |
| 2112 @samp{-t} in @code{wdiff}. | |
| 2113 | |
| 2114 @item text | |
| 2115 @samp{-a} in @code{diff}. | |
| 2116 | |
| 2117 @item text-files | |
| 2118 @samp{-T} in @code{shar}. | |
| 2119 | |
| 2120 @item time | |
| 2121 Used in @code{ls} and @code{touch}. | |
| 2122 | |
| 2123 @item timeout | |
| 2124 Specify how long to wait before giving up on some operation. | |
| 2125 | |
| 2126 @item to-stdout | |
| 2127 @samp{-O} in @code{tar}. | |
| 2128 | |
| 2129 @item total | |
| 2130 @samp{-c} in @code{du}. | |
| 2131 | |
| 2132 @item touch | |
| 10199 | 2133 @samp{-t} in @code{make}, @code{ranlib}, and @code{recode}. |
| 4958 | 2134 |
| 2135 @item trace | |
| 2136 @samp{-t} in @code{m4}. | |
| 2137 | |
| 2138 @item traditional | |
| 2139 @samp{-t} in @code{hello}; | |
| 2140 @samp{-W traditional} in @code{gawk}; | |
| 2141 @samp{-G} in @code{ed}, @code{m4}, and @code{ptx}. | |
| 2142 | |
| 2143 @item tty | |
| 2144 Used in GDB. | |
| 2145 | |
| 2146 @item typedefs | |
| 2147 @samp{-t} in @code{ctags}. | |
| 2148 | |
| 2149 @item typedefs-and-c++ | |
| 2150 @samp{-T} in @code{ctags}. | |
| 2151 | |
| 2152 @item typeset-mode | |
| 2153 @samp{-t} in @code{ptx}. | |
| 2154 | |
| 2155 @item uncompress | |
| 2156 @samp{-z} in @code{tar}. | |
| 2157 | |
| 2158 @item unconditional | |
| 2159 @samp{-u} in @code{cpio}. | |
| 2160 | |
| 2161 @item undefine | |
| 2162 @samp{-U} in @code{m4}. | |
| 2163 | |
| 2164 @item undefined-only | |
| 2165 @samp{-u} in @code{nm}. | |
| 2166 | |
| 2167 @item update | |
| 2168 @samp{-u} in @code{cp}, @code{ctags}, @code{mv}, @code{tar}. | |
| 2169 | |
| 2170 @item usage | |
| 2171 Used in @code{gawk}; same as @samp{--help}. | |
| 2172 | |
| 2173 @item uuencode | |
| 2174 @samp{-B} in @code{shar}. | |
| 2175 | |
| 2176 @item vanilla-operation | |
| 2177 @samp{-V} in @code{shar}. | |
| 2178 | |
| 2179 @item verbose | |
| 2180 Print more information about progress. Many programs support this. | |
| 2181 | |
| 2182 @item verify | |
| 2183 @samp{-W} in @code{tar}. | |
| 2184 | |
| 2185 @item version | |
| 2186 Print the version number. | |
| 2187 | |
| 2188 @item version-control | |
| 2189 @samp{-V} in @code{cp}, @code{ln}, @code{mv}. | |
| 2190 | |
| 2191 @item vgrind | |
| 2192 @samp{-v} in @code{ctags}. | |
| 2193 | |
| 2194 @item volume | |
| 2195 @samp{-V} in @code{tar}. | |
| 2196 | |
| 2197 @item what-if | |
| 10199 | 2198 @samp{-W} in @code{make}. |
| 4958 | 2199 |
| 2200 @item whole-size-limit | |
| 2201 @samp{-l} in @code{shar}. | |
| 2202 | |
| 2203 @item width | |
| 2204 @samp{-w} in @code{ls} and @code{ptx}. | |
| 2205 | |
| 2206 @item word-regexp | |
| 2207 @samp{-W} in @code{ptx}. | |
| 2208 | |
| 2209 @item writable | |
| 2210 @samp{-T} in @code{who}. | |
| 2211 | |
| 2212 @item zeros | |
| 2213 @samp{-z} in @code{gprof}. | |
| 2214 @end table | |
| 2215 | |
| 2216 @node Memory Usage | |
| 2217 @section Memory Usage | |
| 2218 @cindex memory usage | |
| 2219 | |
| 2220 If a program typically uses just a few meg of memory, don't bother making any | |
| 2221 effort to reduce memory usage. For example, if it is impractical for | |
| 2222 other reasons to operate on files more than a few meg long, it is | |
| 7663 | 2223 reasonable to read entire input files into memory to operate on them. |
| 4958 | 2224 |
| 2225 However, for programs such as @code{cat} or @code{tail}, that can | |
| 2226 usefully operate on very large files, it is important to avoid using a | |
| 2227 technique that would artificially limit the size of files it can handle. | |
| 2228 If a program works by lines and could be applied to arbitrary | |
| 2229 user-supplied input files, it should keep only a line in memory, because | |
| 2230 this is not very hard and users will want to be able to operate on input | |
| 7663 | 2231 files that are bigger than will fit in memory all at once. |
| 4958 | 2232 |
| 2233 If your program creates complicated data structures, just make them in | |
| 7663 | 2234 memory and give a fatal error if @code{malloc} returns zero. |
| 4958 | 2235 |
| 2236 @node File Usage | |
| 2237 @section File Usage | |
| 2238 @cindex file usage | |
| 2239 | |
| 2240 Programs should be prepared to operate when @file{/usr} and @file{/etc} | |
| 2241 are read-only file systems. Thus, if the program manages log files, | |
| 2242 lock files, backup files, score files, or any other files which are | |
| 2243 modified for internal purposes, these files should not be stored in | |
| 2244 @file{/usr} or @file{/etc}. | |
| 2245 | |
| 2246 There are two exceptions. @file{/etc} is used to store system | |
| 2247 configuration information; it is reasonable for a program to modify | |
| 2248 files in @file{/etc} when its job is to update the system configuration. | |
| 2249 Also, if the user explicitly asks to modify one file in a directory, it | |
| 2250 is reasonable for the program to store other files in the same | |
| 2251 directory. | |
| 2252 | |
| 2253 @node Writing C | |
| 2254 @chapter Making The Best Use of C | |
| 2255 | |
| 5301 | 2256 This chapter provides advice on how best to use the C language |
| 4958 | 2257 when writing GNU software. |
| 2258 | |
| 2259 @menu | |
| 9115 | 2260 * Formatting:: Formatting your source code. |
| 2261 * Comments:: Commenting your work. | |
| 2262 * Syntactic Conventions:: Clean use of C constructs. | |
| 2263 * Names:: Naming variables, functions, and files. | |
| 2264 * System Portability:: Portability among different operating systems. | |
| 2265 * CPU Portability:: Supporting the range of CPU types. | |
| 2266 * System Functions:: Portability and ``standard'' library functions. | |
| 2267 * Internationalization:: Techniques for internationalization. | |
| 6066 | 2268 * Character Set:: Use ASCII by default. |
| 2269 * Quote Characters:: Use `...' in the C locale. | |
| 4958 | 2270 * Mmap:: How you can safely use @code{mmap}. |
| 2271 @end menu | |
| 2272 | |
| 2273 @node Formatting | |
| 2274 @section Formatting Your Source Code | |
| 2275 @cindex formatting source code | |
| 2276 | |
| 2277 @cindex open brace | |
| 2278 @cindex braces, in C source | |
| 2279 It is important to put the open-brace that starts the body of a C | |
| 7703 | 2280 function in column one, so that they will start a defun. Several |
| 2281 tools look for open-braces in column one to find the beginnings of C | |
| 2282 functions. These tools will not work on code not formatted that way. | |
| 2283 | |
| 2284 Avoid putting open-brace, open-parenthesis or open-bracket in column | |
| 2285 one when they are inside a function, so that they won't start a defun. | |
| 2286 The open-brace that starts a @code{struct} body can go in column one | |
| 2287 if you find it useful to treat that definition as a defun. | |
| 4958 | 2288 |
| 2289 It is also important for function definitions to start the name of the | |
| 6498 | 2290 function in column one. This helps people to search for function |
| 4958 | 2291 definitions, and may also help certain tools recognize them. Thus, |
| 5909 | 2292 using Standard C syntax, the format is this: |
| 4958 | 2293 |
| 2294 @example | |
| 2295 static char * | |
| 5909 | 2296 concat (char *s1, char *s2) |
| 2297 @{ | |
| 4958 | 2298 @dots{} |
| 2299 @} | |
| 2300 @end example | |
| 2301 | |
| 2302 @noindent | |
| 6725 | 2303 or, if you want to use traditional C syntax, format the definition like |
| 4958 | 2304 this: |
| 2305 | |
| 2306 @example | |
| 2307 static char * | |
| 6498 | 2308 concat (s1, s2) /* Name starts in column one here */ |
| 5909 | 2309 char *s1, *s2; |
| 6498 | 2310 @{ /* Open brace in column one here */ |
| 4958 | 2311 @dots{} |
| 2312 @} | |
| 2313 @end example | |
| 2314 | |
| 2315 In Standard C, if the arguments don't fit nicely on one line, | |
| 2316 split it like this: | |
| 2317 | |
| 2318 @example | |
| 2319 int | |
| 2320 lots_of_args (int an_integer, long a_long, short a_short, | |
| 2321 double a_double, float a_float) | |
| 2322 @dots{} | |
| 2323 @end example | |
| 2324 | |
| 2325 The rest of this section gives our recommendations for other aspects of | |
| 2326 C formatting style, which is also the default style of the @code{indent} | |
| 2327 program in version 1.2 and newer. It corresponds to the options | |
| 2328 | |
| 2329 @smallexample | |
| 2330 -nbad -bap -nbc -bbo -bl -bli2 -bls -ncdb -nce -cp1 -cs -di2 | |
| 2331 -ndj -nfc1 -nfca -hnl -i2 -ip5 -lp -pcs -psl -nsc -nsob | |
| 2332 @end smallexample | |
| 2333 | |
| 2334 We don't think of these recommendations as requirements, because it | |
| 2335 causes no problems for users if two different programs have different | |
| 2336 formatting styles. | |
| 2337 | |
| 2338 But whatever style you use, please use it consistently, since a mixture | |
| 2339 of styles within one program tends to look ugly. If you are | |
| 2340 contributing changes to an existing program, please follow the style of | |
| 2341 that program. | |
| 2342 | |
| 2343 For the body of the function, our recommended style looks like this: | |
| 2344 | |
| 2345 @example | |
| 2346 if (x < foo (y, z)) | |
| 2347 haha = bar[4] + 5; | |
| 2348 else | |
| 2349 @{ | |
| 2350 while (z) | |
| 2351 @{ | |
| 2352 haha += foo (z, z); | |
| 2353 z--; | |
| 2354 @} | |
| 2355 return ++x + bar (); | |
| 2356 @} | |
| 2357 @end example | |
| 2358 | |
| 2359 @cindex spaces before open-paren | |
| 2360 We find it easier to read a program when it has spaces before the | |
| 2361 open-parentheses and after the commas. Especially after the commas. | |
| 2362 | |
| 2363 When you split an expression into multiple lines, split it | |
| 2364 before an operator, not after one. Here is the right way: | |
| 2365 | |
| 2366 @cindex expressions, splitting | |
| 2367 @example | |
| 2368 if (foo_this_is_long && bar > win (x, y, z) | |
| 2369 && remaining_condition) | |
| 2370 @end example | |
| 2371 | |
| 2372 Try to avoid having two operators of different precedence at the same | |
| 2373 level of indentation. For example, don't write this: | |
| 2374 | |
| 2375 @example | |
| 2376 mode = (inmode[j] == VOIDmode | |
| 2377 || GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]) | |
| 2378 ? outmode[j] : inmode[j]); | |
| 2379 @end example | |
| 2380 | |
| 2381 Instead, use extra parentheses so that the indentation shows the nesting: | |
| 2382 | |
| 2383 @example | |
| 2384 mode = ((inmode[j] == VOIDmode | |
| 2385 || (GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]))) | |
| 2386 ? outmode[j] : inmode[j]); | |
| 2387 @end example | |
| 2388 | |
| 2389 Insert extra parentheses so that Emacs will indent the code properly. | |
| 2390 For example, the following indentation looks nice if you do it by hand, | |
| 2391 | |
| 2392 @example | |
| 2393 v = rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 | |
| 2394 + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000; | |
| 2395 @end example | |
| 2396 | |
| 2397 @noindent | |
| 2398 but Emacs would alter it. Adding a set of parentheses produces | |
| 2399 something that looks equally nice, and which Emacs will preserve: | |
| 2400 | |
| 2401 @example | |
| 2402 v = (rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 | |
| 2403 + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000); | |
| 2404 @end example | |
| 2405 | |
| 2406 Format do-while statements like this: | |
| 2407 | |
| 2408 @example | |
| 2409 do | |
| 2410 @{ | |
| 2411 a = foo (a); | |
| 2412 @} | |
| 2413 while (a > 0); | |
| 2414 @end example | |
| 2415 | |
| 2416 @cindex formfeed | |
| 2417 @cindex control-L | |
| 2418 Please use formfeed characters (control-L) to divide the program into | |
| 2419 pages at logical places (but not within a function). It does not matter | |
| 2420 just how long the pages are, since they do not have to fit on a printed | |
| 2421 page. The formfeeds should appear alone on lines by themselves. | |
| 2422 | |
| 2423 @node Comments | |
| 2424 @section Commenting Your Work | |
| 2425 @cindex commenting | |
| 2426 | |
| 2427 Every program should start with a comment saying briefly what it is for. | |
| 6066 | 2428 Example: @samp{fmt - filter for simple filling of text}. This comment |
| 2429 should be at the top of the source file containing the @samp{main} | |
| 2430 function of the program. | |
| 2431 | |
| 2432 Also, please write a brief comment at the start of each source file, | |
| 2433 with the file name and a line or two about the overall purpose of the | |
| 2434 file. | |
| 4958 | 2435 |
| 2436 Please write the comments in a GNU program in English, because English | |
| 2437 is the one language that nearly all programmers in all countries can | |
| 2438 read. If you do not write English well, please write comments in | |
| 2439 English as well as you can, then ask other people to help rewrite them. | |
| 2440 If you can't write comments in English, please find someone to work with | |
| 2441 you and translate your comments into English. | |
| 2442 | |
| 2443 Please put a comment on each function saying what the function does, | |
| 2444 what sorts of arguments it gets, and what the possible values of | |
| 2445 arguments mean and are used for. It is not necessary to duplicate in | |
| 2446 words the meaning of the C argument declarations, if a C type is being | |
| 2447 used in its customary fashion. If there is anything nonstandard about | |
| 2448 its use (such as an argument of type @code{char *} which is really the | |
| 2449 address of the second character of a string, not the first), or any | |
| 2450 possible values that would not work the way one would expect (such as, | |
| 2451 that strings containing newlines are not guaranteed to work), be sure | |
| 2452 to say so. | |
| 2453 | |
| 2454 Also explain the significance of the return value, if there is one. | |
| 2455 | |
| 2456 Please put two spaces after the end of a sentence in your comments, so | |
| 2457 that the Emacs sentence commands will work. Also, please write | |
| 2458 complete sentences and capitalize the first word. If a lower-case | |
| 2459 identifier comes at the beginning of a sentence, don't capitalize it! | |
| 2460 Changing the spelling makes it a different identifier. If you don't | |
| 2461 like starting a sentence with a lower case letter, write the sentence | |
| 2462 differently (e.g., ``The identifier lower-case is @dots{}''). | |
| 2463 | |
| 2464 The comment on a function is much clearer if you use the argument | |
| 2465 names to speak about the argument values. The variable name itself | |
| 2466 should be lower case, but write it in upper case when you are speaking | |
| 2467 about the value rather than the variable itself. Thus, ``the inode | |
| 2468 number NODE_NUM'' rather than ``an inode''. | |
| 2469 | |
| 2470 There is usually no purpose in restating the name of the function in | |
| 2471 the comment before it, because the reader can see that for himself. | |
| 2472 There might be an exception when the comment is so long that the function | |
| 2473 itself would be off the bottom of the screen. | |
| 2474 | |
| 2475 There should be a comment on each static variable as well, like this: | |
| 2476 | |
| 2477 @example | |
| 2478 /* Nonzero means truncate lines in the display; | |
| 2479 zero means continue them. */ | |
| 2480 int truncate_lines; | |
| 2481 @end example | |
| 2482 | |
| 2483 @cindex conditionals, comments for | |
| 2484 @cindex @code{#endif}, commenting | |
| 2485 Every @samp{#endif} should have a comment, except in the case of short | |
| 2486 conditionals (just a few lines) that are not nested. The comment should | |
| 2487 state the condition of the conditional that is ending, @emph{including | |
| 2488 its sense}. @samp{#else} should have a comment describing the condition | |
| 2489 @emph{and sense} of the code that follows. For example: | |
| 2490 | |
| 2491 @example | |
| 2492 @group | |
| 2493 #ifdef foo | |
| 2494 @dots{} | |
| 2495 #else /* not foo */ | |
| 2496 @dots{} | |
| 2497 #endif /* not foo */ | |
| 2498 @end group | |
| 2499 @group | |
| 2500 #ifdef foo | |
| 2501 @dots{} | |
| 2502 #endif /* foo */ | |
| 2503 @end group | |
| 2504 @end example | |
| 2505 | |
| 2506 @noindent | |
| 2507 but, by contrast, write the comments this way for a @samp{#ifndef}: | |
| 2508 | |
| 2509 @example | |
| 2510 @group | |
| 2511 #ifndef foo | |
| 2512 @dots{} | |
| 2513 #else /* foo */ | |
| 2514 @dots{} | |
| 2515 #endif /* foo */ | |
| 2516 @end group | |
| 2517 @group | |
| 2518 #ifndef foo | |
| 2519 @dots{} | |
| 2520 #endif /* not foo */ | |
| 2521 @end group | |
| 2522 @end example | |
| 2523 | |
| 2524 @node Syntactic Conventions | |
| 2525 @section Clean Use of C Constructs | |
| 2526 @cindex syntactic conventions | |
| 2527 | |
| 2528 @cindex implicit @code{int} | |
| 2529 @cindex function argument, declaring | |
| 2530 Please explicitly declare the types of all objects. For example, you | |
| 2531 should explicitly declare all arguments to functions, and you should | |
| 2532 declare functions to return @code{int} rather than omitting the | |
| 2533 @code{int}. | |
| 2534 | |
| 2535 @cindex compiler warnings | |
| 2536 @cindex @samp{-Wall} compiler option | |
| 2537 Some programmers like to use the GCC @samp{-Wall} option, and change the | |
| 2538 code whenever it issues a warning. If you want to do this, then do. | |
| 2539 Other programmers prefer not to use @samp{-Wall}, because it gives | |
| 2540 warnings for valid and legitimate code which they do not want to change. | |
| 2541 If you want to do this, then do. The compiler should be your servant, | |
| 2542 not your master. | |
| 2543 | |
| 2544 Declarations of external functions and functions to appear later in the | |
| 2545 source file should all go in one place near the beginning of the file | |
| 2546 (somewhere before the first function definition in the file), or else | |
| 2547 should go in a header file. Don't put @code{extern} declarations inside | |
| 2548 functions. | |
| 2549 | |
| 2550 @cindex temporary variables | |
| 2551 It used to be common practice to use the same local variables (with | |
| 2552 names like @code{tem}) over and over for different values within one | |
| 2553 function. Instead of doing this, it is better to declare a separate local | |
| 2554 variable for each distinct purpose, and give it a name which is | |
| 2555 meaningful. This not only makes programs easier to understand, it also | |
| 2556 facilitates optimization by good compilers. You can also move the | |
| 2557 declaration of each local variable into the smallest scope that includes | |
| 2558 all its uses. This makes the program even cleaner. | |
| 2559 | |
| 2560 Don't use local variables or parameters that shadow global identifiers. | |
| 2561 | |
| 2562 @cindex multiple variables in a line | |
| 2563 Don't declare multiple variables in one declaration that spans lines. | |
| 2564 Start a new declaration on each line, instead. For example, instead | |
| 2565 of this: | |
| 2566 | |
| 2567 @example | |
| 2568 @group | |
| 2569 int foo, | |
| 2570 bar; | |
| 2571 @end group | |
| 2572 @end example | |
| 2573 | |
| 2574 @noindent | |
| 2575 write either this: | |
| 2576 | |
| 2577 @example | |
| 2578 int foo, bar; | |
| 2579 @end example | |
| 2580 | |
| 2581 @noindent | |
| 2582 or this: | |
| 2583 | |
| 2584 @example | |
| 2585 int foo; | |
| 2586 int bar; | |
| 2587 @end example | |
| 2588 | |
| 2589 @noindent | |
| 2590 (If they are global variables, each should have a comment preceding it | |
| 2591 anyway.) | |
| 2592 | |
| 2593 When you have an @code{if}-@code{else} statement nested in another | |
| 2594 @code{if} statement, always put braces around the @code{if}-@code{else}. | |
| 2595 Thus, never write like this: | |
| 2596 | |
| 2597 @example | |
| 2598 if (foo) | |
| 2599 if (bar) | |
| 2600 win (); | |
| 2601 else | |
| 2602 lose (); | |
| 2603 @end example | |
| 2604 | |
| 2605 @noindent | |
| 2606 always like this: | |
| 2607 | |
| 2608 @example | |
| 2609 if (foo) | |
| 2610 @{ | |
| 2611 if (bar) | |
| 2612 win (); | |
| 2613 else | |
| 2614 lose (); | |
| 2615 @} | |
| 2616 @end example | |
| 2617 | |
| 2618 If you have an @code{if} statement nested inside of an @code{else} | |
| 2619 statement, either write @code{else if} on one line, like this, | |
| 2620 | |
| 2621 @example | |
| 2622 if (foo) | |
| 2623 @dots{} | |
| 2624 else if (bar) | |
| 2625 @dots{} | |
| 2626 @end example | |
| 2627 | |
| 2628 @noindent | |
| 2629 with its @code{then}-part indented like the preceding @code{then}-part, | |
| 2630 or write the nested @code{if} within braces like this: | |
| 2631 | |
| 2632 @example | |
| 2633 if (foo) | |
| 2634 @dots{} | |
| 2635 else | |
| 2636 @{ | |
| 2637 if (bar) | |
| 2638 @dots{} | |
| 2639 @} | |
| 2640 @end example | |
| 2641 | |
| 2642 Don't declare both a structure tag and variables or typedefs in the | |
| 2643 same declaration. Instead, declare the structure tag separately | |
| 2644 and then use it to declare the variables or typedefs. | |
| 2645 | |
| 7663 | 2646 Try to avoid assignments inside @code{if}-conditions (assignments |
| 2647 inside @code{while}-conditions are ok). For example, don't write | |
| 2648 this: | |
| 4958 | 2649 |
| 2650 @example | |
| 2651 if ((foo = (char *) malloc (sizeof *foo)) == 0) | |
| 2652 fatal ("virtual memory exhausted"); | |
| 2653 @end example | |
| 2654 | |
| 2655 @noindent | |
| 2656 instead, write this: | |
| 2657 | |
| 2658 @example | |
| 2659 foo = (char *) malloc (sizeof *foo); | |
| 2660 if (foo == 0) | |
| 2661 fatal ("virtual memory exhausted"); | |
| 2662 @end example | |
| 2663 | |
| 2664 @pindex lint | |
| 2665 Don't make the program ugly to placate @code{lint}. Please don't insert any | |
| 2666 casts to @code{void}. Zero without a cast is perfectly fine as a null | |
| 2667 pointer constant, except when calling a varargs function. | |
| 2668 | |
| 2669 @node Names | |
| 2670 @section Naming Variables, Functions, and Files | |
| 2671 | |
| 2672 @cindex names of variables, functions, and files | |
| 2673 The names of global variables and functions in a program serve as | |
| 2674 comments of a sort. So don't choose terse names---instead, look for | |
| 2675 names that give useful information about the meaning of the variable or | |
| 2676 function. In a GNU program, names should be English, like other | |
| 2677 comments. | |
| 2678 | |
| 2679 Local variable names can be shorter, because they are used only within | |
| 2680 one context, where (presumably) comments explain their purpose. | |
| 2681 | |
| 2682 Try to limit your use of abbreviations in symbol names. It is ok to | |
| 2683 make a few abbreviations, explain what they mean, and then use them | |
| 2684 frequently, but don't use lots of obscure abbreviations. | |
| 2685 | |
| 2686 Please use underscores to separate words in a name, so that the Emacs | |
| 2687 word commands can be useful within them. Stick to lower case; reserve | |
| 2688 upper case for macros and @code{enum} constants, and for name-prefixes | |
| 2689 that follow a uniform convention. | |
| 2690 | |
| 2691 For example, you should use names like @code{ignore_space_change_flag}; | |
| 2692 don't use names like @code{iCantReadThis}. | |
| 2693 | |
| 2694 Variables that indicate whether command-line options have been | |
| 2695 specified should be named after the meaning of the option, not after | |
| 2696 the option-letter. A comment should state both the exact meaning of | |
| 2697 the option and its letter. For example, | |
| 2698 | |
| 2699 @example | |
| 2700 @group | |
| 2701 /* Ignore changes in horizontal whitespace (-b). */ | |
| 2702 int ignore_space_change_flag; | |
| 2703 @end group | |
| 2704 @end example | |
| 2705 | |
| 2706 When you want to define names with constant integer values, use | |
| 2707 @code{enum} rather than @samp{#define}. GDB knows about enumeration | |
| 2708 constants. | |
| 2709 | |
| 2710 @cindex file-name limitations | |
| 2711 @pindex doschk | |
| 2712 You might want to make sure that none of the file names would conflict | |
| 6498 | 2713 if the files were loaded onto an MS-DOS file system which shortens the |
| 4958 | 2714 names. You can use the program @code{doschk} to test for this. |
| 2715 | |
| 2716 Some GNU programs were designed to limit themselves to file names of 14 | |
| 2717 characters or less, to avoid file name conflicts if they are read into | |
| 2718 older System V systems. Please preserve this feature in the existing | |
| 2719 GNU programs that have it, but there is no need to do this in new GNU | |
| 2720 programs. @code{doschk} also reports file names longer than 14 | |
| 2721 characters. | |
| 2722 | |
| 2723 @node System Portability | |
| 2724 @section Portability between System Types | |
| 2725 @cindex portability, between system types | |
| 2726 | |
| 2727 In the Unix world, ``portability'' refers to porting to different Unix | |
| 2728 versions. For a GNU program, this kind of portability is desirable, but | |
| 2729 not paramount. | |
| 2730 | |
| 2731 The primary purpose of GNU software is to run on top of the GNU kernel, | |
| 2732 compiled with the GNU C compiler, on various types of @sc{cpu}. So the | |
| 2733 kinds of portability that are absolutely necessary are quite limited. | |
| 2734 But it is important to support Linux-based GNU systems, since they | |
| 2735 are the form of GNU that is popular. | |
| 2736 | |
| 2737 Beyond that, it is good to support the other free operating systems | |
| 2738 (*BSD), and it is nice to support other Unix-like systems if you want | |
| 2739 to. Supporting a variety of Unix-like systems is desirable, although | |
| 2740 not paramount. It is usually not too hard, so you may as well do it. | |
| 2741 But you don't have to consider it an obligation, if it does turn out to | |
| 2742 be hard. | |
| 2743 | |
| 2744 @pindex autoconf | |
| 2745 The easiest way to achieve portability to most Unix-like systems is to | |
| 2746 use Autoconf. It's unlikely that your program needs to know more | |
| 2747 information about the host platform than Autoconf can provide, simply | |
| 2748 because most of the programs that need such knowledge have already been | |
| 2749 written. | |
| 2750 | |
| 2751 Avoid using the format of semi-internal data bases (e.g., directories) | |
| 2752 when there is a higher-level alternative (@code{readdir}). | |
| 2753 | |
| 2754 @cindex non-@sc{posix} systems, and portability | |
| 6066 | 2755 As for systems that are not like Unix, such as MSDOS, Windows, VMS, MVS, |
| 2756 and older Macintosh systems, supporting them is often a lot of work. | |
| 2757 When that is the case, it is better to spend your time adding features | |
| 2758 that will be useful on GNU and GNU/Linux, rather than on supporting | |
| 2759 other incompatible systems. | |
| 4958 | 2760 |
| 2761 If you do support Windows, please do not abbreviate it as ``win''. In | |
| 2762 hacker terminology, calling something a ``win'' is a form of praise. | |
| 2763 You're free to praise Microsoft Windows on your own if you want, but | |
| 2764 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
|
2765 ``Windows'' to ``win'', you can write it in full or abbreviate it to |
| 4958 | 2766 ``woe'' or ``w''. In GNU Emacs, for instance, we use @samp{w32} in |
| 2767 file names of Windows-specific files, but the macro for Windows | |
| 2768 conditionals is called @code{WINDOWSNT}. | |
| 2769 | |
| 2770 It is a good idea to define the ``feature test macro'' | |
| 2771 @code{_GNU_SOURCE} when compiling your C files. When you compile on GNU | |
| 2772 or GNU/Linux, this will enable the declarations of GNU library extension | |
| 2773 functions, and that will usually give you a compiler error message if | |
| 2774 you define the same function names in some other way in your program. | |
| 2775 (You don't have to actually @emph{use} these functions, if you prefer | |
| 2776 to make the program more portable to other systems.) | |
| 2777 | |
| 2778 But whether or not you use these GNU extensions, you should avoid | |
| 2779 using their names for any other meanings. Doing so would make it hard | |
| 2780 to move your code into other GNU programs. | |
| 2781 | |
| 2782 @node CPU Portability | |
| 2783 @section Portability between @sc{cpu}s | |
| 2784 | |
| 2785 @cindex data types, and portability | |
| 2786 @cindex portability, and data types | |
| 2787 Even GNU systems will differ because of differences among @sc{cpu} | |
| 2788 types---for example, difference in byte ordering and alignment | |
| 2789 requirements. It is absolutely essential to handle these differences. | |
| 2790 However, don't make any effort to cater to the possibility that an | |
| 2791 @code{int} will be less than 32 bits. We don't support 16-bit machines | |
| 2792 in GNU. | |
| 2793 | |
| 2794 Similarly, don't make any effort to cater to the possibility that | |
| 2795 @code{long} will be smaller than predefined types like @code{size_t}. | |
| 2796 For example, the following code is ok: | |
| 2797 | |
| 2798 @example | |
| 2799 printf ("size = %lu\n", (unsigned long) sizeof array); | |
| 2800 printf ("diff = %ld\n", (long) (pointer2 - pointer1)); | |
| 2801 @end example | |
| 2802 | |
| 2803 1989 Standard C requires this to work, and we know of only one | |
| 6498 | 2804 counterexample: 64-bit programs on Microsoft Windows. We will |
| 4958 | 2805 leave it to those who want to port GNU programs to that environment |
| 2806 to figure out how to do it. | |
| 2807 | |
| 2808 Predefined file-size types like @code{off_t} are an exception: they are | |
| 2809 longer than @code{long} on many platforms, so code like the above won't | |
| 2810 work with them. One way to print an @code{off_t} value portably is to | |
| 2811 print its digits yourself, one by one. | |
| 2812 | |
| 2813 Don't assume that the address of an @code{int} object is also the | |
| 2814 address of its least-significant byte. This is false on big-endian | |
| 2815 machines. Thus, don't make the following mistake: | |
| 2816 | |
| 2817 @example | |
| 2818 int c; | |
| 2819 @dots{} | |
| 7663 | 2820 while ((c = getchar ()) != EOF) |
| 2821 write (file_descriptor, &c, 1); | |
| 2822 @end example | |
| 2823 | |
| 2824 @noindent Instead, use @code{unsigned char} as follows. (The @code{unsigned} | |
| 2825 is for portability to unusual systems where @code{char} is signed and | |
| 2826 where there is integer overflow checking.) | |
| 2827 | |
| 2828 @example | |
| 2829 int c; | |
| 2830 while ((c = getchar ()) != EOF) | |
| 2831 @{ | |
| 2832 unsigned char u = c; | |
| 2833 write (file_descriptor, &u, 1); | |
| 2834 @} | |
| 4958 | 2835 @end example |
| 2836 | |
| 5566 | 2837 It used to be ok to not worry about the difference between pointers |
| 2838 and integers when passing arguments to functions. However, on most | |
| 2839 modern 64-bit machines pointers are wider than @code{int}. | |
| 2840 Conversely, integer types like @code{long long int} and @code{off_t} | |
| 2841 are wider than pointers on most modern 32-bit machines. Hence it's | |
| 2842 often better nowadays to use prototypes to define functions whose | |
| 2843 argument types are not trivial. | |
| 2844 | |
| 2845 In particular, if functions accept varying argument counts or types | |
| 2846 they should be declared using prototypes containing @samp{...} and | |
| 2847 defined using @file{stdarg.h}. For an example of this, please see the | |
| 2848 @uref{http://www.gnu.org/software/gnulib/, Gnulib} error module, which | |
| 2849 declares and defines the following function: | |
| 4958 | 2850 |
| 2851 @example | |
| 5566 | 2852 /* Print a message with `fprintf (stderr, FORMAT, ...)'; |
| 2853 if ERRNUM is nonzero, follow it with ": " and strerror (ERRNUM). | |
| 2854 If STATUS is nonzero, terminate the program with `exit (STATUS)'. */ | |
| 2855 | |
| 2856 void error (int status, int errnum, const char *format, ...); | |
| 2857 @end example | |
| 2858 | |
| 2859 A simple way to use the Gnulib error module is to obtain the two | |
| 2860 source files @file{error.c} and @file{error.h} from the Gnulib library | |
| 2861 source code repository at | |
| 9823 | 2862 @uref{http://git.savannah.gnu.org/@/gitweb/@/?p=gnulib.git}. |
| 5566 | 2863 Here's a sample use: |
| 2864 | |
| 2865 @example | |
| 2866 #include "error.h" | |
| 2867 #include <errno.h> | |
| 2868 #include <stdio.h> | |
| 2869 | |
| 2870 char *program_name = "myprogram"; | |
| 2871 | |
| 2872 FILE * | |
| 2873 xfopen (char const *name) | |
| 4958 | 2874 @{ |
| 5566 | 2875 FILE *fp = fopen (name, "r"); |
| 2876 if (! fp) | |
| 2877 error (1, errno, "cannot read %s", name); | |
| 2878 return fp; | |
| 4958 | 2879 @} |
| 2880 @end example | |
| 2881 | |
| 2882 @cindex casting pointers to integers | |
| 2883 Avoid casting pointers to integers if you can. Such casts greatly | |
| 2884 reduce portability, and in most programs they are easy to avoid. In the | |
| 2885 cases where casting pointers to integers is essential---such as, a Lisp | |
| 2886 interpreter which stores type information as well as an address in one | |
| 2887 word---you'll have to make explicit provisions to handle different word | |
| 2888 sizes. You will also need to make provision for systems in which the | |
| 2889 normal range of addresses you can get from @code{malloc} starts far away | |
| 2890 from zero. | |
| 2891 | |
| 2892 @node System Functions | |
| 2893 @section Calling System Functions | |
| 2894 @cindex library functions, and portability | |
| 2895 @cindex portability, and library functions | |
| 2896 | |
| 2897 C implementations differ substantially. Standard C reduces but does | |
| 2898 not eliminate the incompatibilities; meanwhile, many GNU packages still | |
| 2899 support pre-standard compilers because this is not hard to do. This | |
| 2900 chapter gives recommendations for how to use the more-or-less standard C | |
| 2901 library functions to avoid unnecessary loss of portability. | |
| 2902 | |
| 2903 @itemize @bullet | |
| 2904 @item | |
| 2905 Don't use the return value of @code{sprintf}. It returns the number of | |
| 2906 characters written on some systems, but not on all systems. | |
| 2907 | |
| 2908 @item | |
| 2909 Be aware that @code{vfprintf} is not always available. | |
| 2910 | |
| 2911 @item | |
| 2912 @code{main} should be declared to return type @code{int}. It should | |
| 2913 terminate either by calling @code{exit} or by returning the integer | |
| 2914 status code; make sure it cannot ever return an undefined value. | |
| 2915 | |
| 2916 @cindex declaration for system functions | |
| 2917 @item | |
| 2918 Don't declare system functions explicitly. | |
| 2919 | |
| 2920 Almost any declaration for a system function is wrong on some system. | |
| 2921 To minimize conflicts, leave it to the system header files to declare | |
| 2922 system functions. If the headers don't declare a function, let it | |
| 2923 remain undeclared. | |
| 2924 | |
| 2925 While it may seem unclean to use a function without declaring it, in | |
| 2926 practice this works fine for most system library functions on the | |
| 2927 systems where this really happens; thus, the disadvantage is only | |
| 2928 theoretical. By contrast, actual declarations have frequently caused | |
| 2929 actual conflicts. | |
| 2930 | |
| 2931 @item | |
| 2932 If you must declare a system function, don't specify the argument types. | |
| 2933 Use an old-style declaration, not a Standard C prototype. The more you | |
| 2934 specify about the function, the more likely a conflict. | |
| 2935 | |
| 2936 @item | |
| 2937 In particular, don't unconditionally declare @code{malloc} or | |
| 2938 @code{realloc}. | |
| 2939 | |
| 2940 Most GNU programs use those functions just once, in functions | |
| 2941 conventionally named @code{xmalloc} and @code{xrealloc}. These | |
| 2942 functions call @code{malloc} and @code{realloc}, respectively, and | |
| 2943 check the results. | |
| 2944 | |
| 2945 Because @code{xmalloc} and @code{xrealloc} are defined in your program, | |
| 2946 you can declare them in other files without any risk of type conflict. | |
| 2947 | |
| 2948 On most systems, @code{int} is the same length as a pointer; thus, the | |
| 2949 calls to @code{malloc} and @code{realloc} work fine. For the few | |
| 2950 exceptional systems (mostly 64-bit machines), you can use | |
| 2951 @strong{conditionalized} declarations of @code{malloc} and | |
| 2952 @code{realloc}---or put these declarations in configuration files | |
| 2953 specific to those systems. | |
| 2954 | |
| 2955 @cindex string library functions | |
| 2956 @item | |
| 2957 The string functions require special treatment. Some Unix systems have | |
| 2958 a header file @file{string.h}; others have @file{strings.h}. Neither | |
| 2959 file name is portable. There are two things you can do: use Autoconf to | |
| 2960 figure out which file to include, or don't include either file. | |
| 2961 | |
| 2962 @item | |
| 2963 If you don't include either strings file, you can't get declarations for | |
| 2964 the string functions from the header file in the usual way. | |
| 2965 | |
| 2966 That causes less of a problem than you might think. The newer standard | |
| 2967 string functions should be avoided anyway because many systems still | |
| 2968 don't support them. The string functions you can use are these: | |
| 2969 | |
| 2970 @example | |
| 2971 strcpy strncpy strcat strncat | |
| 2972 strlen strcmp strncmp | |
| 2973 strchr strrchr | |
| 2974 @end example | |
| 2975 | |
| 2976 The copy and concatenate functions work fine without a declaration as | |
| 2977 long as you don't use their values. Using their values without a | |
| 2978 declaration fails on systems where the width of a pointer differs from | |
| 2979 the width of @code{int}, and perhaps in other cases. It is trivial to | |
| 2980 avoid using their values, so do that. | |
| 2981 | |
| 2982 The compare functions and @code{strlen} work fine without a declaration | |
| 2983 on most systems, possibly all the ones that GNU software runs on. | |
| 2984 You may find it necessary to declare them @strong{conditionally} on a | |
| 2985 few systems. | |
| 2986 | |
| 2987 The search functions must be declared to return @code{char *}. Luckily, | |
| 2988 there is no variation in the data type they return. But there is | |
| 2989 variation in their names. Some systems give these functions the names | |
| 2990 @code{index} and @code{rindex}; other systems use the names | |
| 2991 @code{strchr} and @code{strrchr}. Some systems support both pairs of | |
| 2992 names, but neither pair works on all systems. | |
| 2993 | |
| 2994 You should pick a single pair of names and use it throughout your | |
| 2995 program. (Nowadays, it is better to choose @code{strchr} and | |
| 2996 @code{strrchr} for new programs, since those are the standard | |
| 2997 names.) Declare both of those names as functions returning @code{char | |
| 2998 *}. On systems which don't support those names, define them as macros | |
| 2999 in terms of the other pair. For example, here is what to put at the | |
| 3000 beginning of your file (or in a header) if you want to use the names | |
| 3001 @code{strchr} and @code{strrchr} throughout: | |
| 3002 | |
| 3003 @example | |
| 3004 #ifndef HAVE_STRCHR | |
| 3005 #define strchr index | |
| 3006 #endif | |
| 3007 #ifndef HAVE_STRRCHR | |
| 3008 #define strrchr rindex | |
| 3009 #endif | |
| 3010 | |
| 3011 char *strchr (); | |
| 3012 char *strrchr (); | |
| 3013 @end example | |
| 3014 @end itemize | |
| 3015 | |
| 3016 Here we assume that @code{HAVE_STRCHR} and @code{HAVE_STRRCHR} are | |
| 3017 macros defined in systems where the corresponding functions exist. | |
| 3018 One way to get them properly defined is to use Autoconf. | |
| 3019 | |
| 3020 @node Internationalization | |
| 3021 @section Internationalization | |
| 3022 @cindex internationalization | |
| 3023 | |
| 3024 @pindex gettext | |
| 3025 GNU has a library called GNU gettext that makes it easy to translate the | |
| 3026 messages in a program into various languages. You should use this | |
| 3027 library in every program. Use English for the messages as they appear | |
| 3028 in the program, and let gettext provide the way to translate them into | |
| 3029 other languages. | |
| 3030 | |
| 3031 Using GNU gettext involves putting a call to the @code{gettext} macro | |
| 3032 around each string that might need translation---like this: | |
| 3033 | |
| 3034 @example | |
| 3035 printf (gettext ("Processing file `%s'...")); | |
| 3036 @end example | |
| 3037 | |
| 3038 @noindent | |
| 3039 This permits GNU gettext to replace the string @code{"Processing file | |
| 3040 `%s'..."} with a translated version. | |
| 3041 | |
| 3042 Once a program uses gettext, please make a point of writing calls to | |
| 3043 @code{gettext} when you add new strings that call for translation. | |
| 3044 | |
| 3045 Using GNU gettext in a package involves specifying a @dfn{text domain | |
| 3046 name} for the package. The text domain name is used to separate the | |
| 3047 translations for this package from the translations for other packages. | |
| 3048 Normally, the text domain name should be the same as the name of the | |
| 6801 | 3049 package---for example, @samp{coreutils} for the GNU core utilities. |
| 4958 | 3050 |
| 3051 @cindex message text, and internationalization | |
| 3052 To enable gettext to work well, avoid writing code that makes | |
| 3053 assumptions about the structure of words or sentences. When you want | |
| 3054 the precise text of a sentence to vary depending on the data, use two or | |
| 3055 more alternative string constants each containing a complete sentences, | |
| 3056 rather than inserting conditionalized words or phrases into a single | |
| 3057 sentence framework. | |
| 3058 | |
| 3059 Here is an example of what not to do: | |
| 3060 | |
| 7159 | 3061 @smallexample |
| 6801 | 3062 printf ("%s is full", capacity > 5000000 ? "disk" : "floppy disk"); |
| 7159 | 3063 @end smallexample |
| 4958 | 3064 |
| 6801 | 3065 If you apply gettext to all strings, like this, |
| 4958 | 3066 |
| 7159 | 3067 @smallexample |
| 6801 | 3068 printf (gettext ("%s is full"), |
| 3069 capacity > 5000000 ? gettext ("disk") : gettext ("floppy disk")); | |
| 7159 | 3070 @end smallexample |
| 4958 | 3071 |
| 3072 @noindent | |
| 6801 | 3073 the translator will hardly know that "disk" and "floppy disk" are meant to |
| 3074 be substituted in the other string. Worse, in some languages (like French) | |
| 3075 the construction will not work: the translation of the word "full" depends | |
| 3076 on the gender of the first part of the sentence; it happens to be not the | |
| 3077 same for "disk" as for "floppy disk". | |
| 3078 | |
| 3079 Complete sentences can be translated without problems: | |
| 4958 | 3080 |
| 3081 @example | |
| 6801 | 3082 printf (capacity > 5000000 ? gettext ("disk is full") |
| 3083 : gettext ("floppy disk is full")); | |
| 4958 | 3084 @end example |
| 3085 | |
| 3086 A similar problem appears at the level of sentence structure with this | |
| 3087 code: | |
| 3088 | |
| 3089 @example | |
| 3090 printf ("# Implicit rule search has%s been done.\n", | |
| 3091 f->tried_implicit ? "" : " not"); | |
| 3092 @end example | |
| 3093 | |
| 3094 @noindent | |
| 3095 Adding @code{gettext} calls to this code cannot give correct results for | |
| 3096 all languages, because negation in some languages requires adding words | |
| 3097 at more than one place in the sentence. By contrast, adding | |
| 6946 | 3098 @code{gettext} calls does the job straightforwardly if the code starts |
| 4958 | 3099 out like this: |
| 3100 | |
| 3101 @example | |
| 3102 printf (f->tried_implicit | |
| 3103 ? "# Implicit rule search has been done.\n", | |
| 3104 : "# Implicit rule search has not been done.\n"); | |
| 3105 @end example | |
| 3106 | |
| 6801 | 3107 Another example is this one: |
| 3108 | |
| 3109 @example | |
| 3110 printf ("%d file%s processed", nfiles, | |
| 3111 nfiles != 1 ? "s" : ""); | |
| 3112 @end example | |
| 3113 | |
| 3114 @noindent | |
| 3115 The problem with this example is that it assumes that plurals are made | |
| 3116 by adding `s'. If you apply gettext to the format string, like this, | |
| 3117 | |
| 3118 @example | |
| 3119 printf (gettext ("%d file%s processed"), nfiles, | |
| 3120 nfiles != 1 ? "s" : ""); | |
| 3121 @end example | |
| 3122 | |
| 3123 @noindent | |
| 3124 the message can use different words, but it will still be forced to use | |
| 3125 `s' for the plural. Here is a better way, with gettext being applied to | |
| 3126 the two strings independently: | |
| 3127 | |
| 3128 @example | |
| 3129 printf ((nfiles != 1 ? gettext ("%d files processed") | |
| 3130 : gettext ("%d file processed")), | |
| 3131 nfiles); | |
| 3132 @end example | |
| 3133 | |
| 3134 @noindent | |
| 3135 But this still doesn't work for languages like Polish, which has three | |
| 3136 plural forms: one for nfiles == 1, one for nfiles == 2, 3, 4, 22, 23, 24, ... | |
| 3137 and one for the rest. The GNU @code{ngettext} function solves this problem: | |
| 3138 | |
| 3139 @example | |
| 3140 printf (ngettext ("%d files processed", "%d file processed", nfiles), | |
| 3141 nfiles); | |
| 3142 @end example | |
| 3143 | |
| 6066 | 3144 |
| 3145 @node Character Set | |
| 3146 @section Character Set | |
| 3147 @cindex character set | |
| 3148 @cindex encodings | |
| 3149 @cindex ASCII characters | |
| 3150 @cindex non-ASCII characters | |
| 3151 | |
| 3152 Sticking to the ASCII character set (plain text, 7-bit characters) is | |
| 3153 preferred in GNU source code comments, text documents, and other | |
| 3154 contexts, unless there is good reason to do something else because of | |
| 3155 the application domain. For example, if source code deals with the | |
| 3156 French Revolutionary calendar, it is OK if its literal strings contain | |
| 3157 accented characters in month names like ``Flor@'eal''. Also, it is OK | |
| 3158 to use non-ASCII characters to represent proper names of contributors in | |
| 3159 change logs (@pxref{Change Logs}). | |
| 3160 | |
| 3161 If you need to use non-ASCII characters, you should normally stick with | |
| 3162 one encoding, as one cannot in general mix encodings reliably. | |
| 3163 | |
| 3164 | |
| 3165 @node Quote Characters | |
| 3166 @section Quote Characters | |
| 3167 @cindex quote characters | |
| 3168 @cindex locale-specific quote characters | |
| 3169 @cindex left quote | |
| 3170 @cindex grave accent | |
| 3171 | |
| 3172 In the C locale, GNU programs should stick to plain ASCII for quotation | |
| 3173 characters in messages to users: preferably 0x60 (@samp{`}) for left | |
| 3174 quotes and 0x27 (@samp{'}) for right quotes. It is ok, but not | |
| 3175 required, to use locale-specific quotes in other locales. | |
| 3176 | |
| 3177 The @uref{http://www.gnu.org/software/gnulib/, Gnulib} @code{quote} and | |
| 3178 @code{quotearg} modules provide a reasonably straightforward way to | |
| 3179 support locale-specific quote characters, as well as taking care of | |
| 3180 other issues, such as quoting a filename that itself contains a quote | |
| 3181 character. See the Gnulib documentation for usage details. | |
| 3182 | |
| 3183 In any case, the documentation for your program should clearly specify | |
| 3184 how it does quoting, if different than the preferred method of @samp{`} | |
| 3185 and @samp{'}. This is especially important if the output of your | |
| 3186 program is ever likely to be parsed by another program. | |
| 3187 | |
| 6498 | 3188 Quotation characters are a difficult area in the computing world at |
| 3189 this time: there are no true left or right quote characters in Latin1; | |
| 3190 the @samp{`} character we use was standardized there as a grave | |
| 6066 | 3191 accent. Moreover, Latin1 is still not universally usable. |
| 3192 | |
| 3193 Unicode contains the unambiguous quote characters required, and its | |
| 6498 | 3194 common encoding UTF-8 is upward compatible with Latin1. However, |
| 6725 | 3195 Unicode and UTF-8 are not universally well-supported, either. |
| 6066 | 3196 |
| 3197 This may change over the next few years, and then we will revisit | |
| 3198 this. | |
| 3199 | |
| 3200 | |
| 4958 | 3201 @node Mmap |
| 3202 @section Mmap | |
| 3203 @findex mmap | |
| 3204 | |
| 3205 Don't assume that @code{mmap} either works on all files or fails | |
| 3206 for all files. It may work on some files and fail on others. | |
| 3207 | |
| 3208 The proper way to use @code{mmap} is to try it on the specific file for | |
| 3209 which you want to use it---and if @code{mmap} doesn't work, fall back on | |
| 3210 doing the job in another way using @code{read} and @code{write}. | |
| 3211 | |
| 3212 The reason this precaution is needed is that the GNU kernel (the HURD) | |
| 3213 provides a user-extensible file system, in which there can be many | |
| 3214 different kinds of ``ordinary files.'' Many of them support | |
| 3215 @code{mmap}, but some do not. It is important to make programs handle | |
| 3216 all these kinds of files. | |
| 3217 | |
| 3218 @node Documentation | |
| 3219 @chapter Documenting Programs | |
| 3220 @cindex documentation | |
| 3221 | |
| 3222 A GNU program should ideally come with full free documentation, adequate | |
| 3223 for both reference and tutorial purposes. If the package can be | |
| 3224 programmed or extended, the documentation should cover programming or | |
| 3225 extending it, as well as just using it. | |
| 3226 | |
| 3227 @menu | |
| 3228 * GNU Manuals:: Writing proper manuals. | |
| 3229 * Doc Strings and Manuals:: Compiling doc strings doesn't make a manual. | |
| 3230 * Manual Structure Details:: Specific structure conventions. | |
| 3231 * License for Manuals:: Writing the distribution terms for a manual. | |
| 3232 * Manual Credits:: Giving credit to documentation contributors. | |
| 3233 * Printed Manuals:: Mentioning the printed manual. | |
| 3234 * NEWS File:: NEWS files supplement manuals. | |
| 9115 | 3235 * Change Logs:: Recording changes. |
| 4958 | 3236 * Man Pages:: Man pages are secondary. |
| 3237 * Reading other Manuals:: How far you can go in learning | |
| 3238 from other manuals. | |
| 3239 @end menu | |
| 3240 | |
| 3241 @node GNU Manuals | |
| 3242 @section GNU Manuals | |
| 3243 | |
| 3244 The preferred document format for the GNU system is the Texinfo | |
| 3245 formatting language. Every GNU package should (ideally) have | |
| 3246 documentation in Texinfo both for reference and for learners. Texinfo | |
| 3247 makes it possible to produce a good quality formatted book, using | |
| 3248 @TeX{}, and to generate an Info file. It is also possible to generate | |
| 3249 HTML output from Texinfo source. See the Texinfo manual, either the | |
| 3250 hardcopy, or the on-line version available through @code{info} or the | |
| 3251 Emacs Info subsystem (@kbd{C-h i}). | |
| 3252 | |
| 3253 Nowadays some other formats such as Docbook and Sgmltexi can be | |
| 3254 converted automatically into Texinfo. It is ok to produce the Texinfo | |
| 3255 documentation by conversion this way, as long as it gives good results. | |
| 3256 | |
| 6775 | 3257 Make sure your manual is clear to a reader who knows nothing about the |
| 3258 topic and reads it straight through. This means covering basic topics | |
| 3259 at the beginning, and advanced topics only later. This also means | |
| 3260 defining every specialized term when it is first used. | |
| 3261 | |
| 3262 Programmers tend to carry over the structure of the program as the | |
| 3263 structure for its documentation. But this structure is not | |
| 3264 necessarily good for explaining how to use the program; it may be | |
| 3265 irrelevant and confusing for a user. | |
| 3266 | |
| 3267 Instead, the right way to structure documentation is according to the | |
| 3268 concepts and questions that a user will have in mind when reading it. | |
| 3269 This principle applies at every level, from the lowest (ordering | |
| 3270 sentences in a paragraph) to the highest (ordering of chapter topics | |
| 3271 within the manual). Sometimes this structure of ideas matches the | |
| 4958 | 3272 structure of the implementation of the software being documented---but |
| 6775 | 3273 often they are different. An important part of learning to write good |
| 3274 documentation is to learn to notice when you have unthinkingly | |
| 3275 structured the documentation like the implementation, stop yourself, | |
| 3276 and look for better alternatives. | |
| 4958 | 3277 |
| 3278 For example, each program in the GNU system probably ought to be | |
| 3279 documented in one manual; but this does not mean each program should | |
| 3280 have its own manual. That would be following the structure of the | |
| 3281 implementation, rather than the structure that helps the user | |
| 3282 understand. | |
| 3283 | |
| 3284 Instead, each manual should cover a coherent @emph{topic}. For example, | |
| 3285 instead of a manual for @code{diff} and a manual for @code{diff3}, we | |
| 3286 have one manual for ``comparison of files'' which covers both of those | |
| 3287 programs, as well as @code{cmp}. By documenting these programs | |
| 3288 together, we can make the whole subject clearer. | |
| 3289 | |
| 3290 The manual which discusses a program should certainly document all of | |
| 3291 the program's command-line options and all of its commands. It should | |
| 3292 give examples of their use. But don't organize the manual as a list | |
| 3293 of features. Instead, organize it logically, by subtopics. Address | |
| 3294 the questions that a user will ask when thinking about the job that | |
| 3295 the program does. Don't just tell the reader what each feature can | |
| 3296 do---say what jobs it is good for, and show how to use it for those | |
| 3297 jobs. Explain what is recommended usage, and what kinds of usage | |
| 3298 users should avoid. | |
| 3299 | |
| 3300 In general, a GNU manual should serve both as tutorial and reference. | |
| 3301 It should be set up for convenient access to each topic through Info, | |
| 3302 and for reading straight through (appendixes aside). A GNU manual | |
| 3303 should give a good introduction to a beginner reading through from the | |
| 3304 start, and should also provide all the details that hackers want. | |
| 3305 The Bison manual is a good example of this---please take a look at it | |
| 3306 to see what we mean. | |
| 3307 | |
| 3308 That is not as hard as it first sounds. Arrange each chapter as a | |
| 3309 logical breakdown of its topic, but order the sections, and write their | |
| 3310 text, so that reading the chapter straight through makes sense. Do | |
| 3311 likewise when structuring the book into chapters, and when structuring a | |
| 3312 section into paragraphs. The watchword is, @emph{at each point, address | |
| 3313 the most fundamental and important issue raised by the preceding text.} | |
| 3314 | |
| 3315 If necessary, add extra chapters at the beginning of the manual which | |
| 3316 are purely tutorial and cover the basics of the subject. These provide | |
| 3317 the framework for a beginner to understand the rest of the manual. The | |
| 3318 Bison manual provides a good example of how to do this. | |
| 3319 | |
| 3320 To serve as a reference, a manual should have an Index that list all the | |
| 3321 functions, variables, options, and important concepts that are part of | |
| 3322 the program. One combined Index should do for a short manual, but | |
| 3323 sometimes for a complex package it is better to use multiple indices. | |
| 3324 The Texinfo manual includes advice on preparing good index entries, see | |
| 5909 | 3325 @ref{Index Entries, , Making Index Entries, texinfo, GNU Texinfo}, and |
| 3326 see @ref{Indexing Commands, , Defining the Entries of an | |
| 3327 Index, texinfo, GNU Texinfo}. | |
| 4958 | 3328 |
| 3329 Don't use Unix man pages as a model for how to write GNU documentation; | |
| 3330 most of them are terse, badly structured, and give inadequate | |
| 3331 explanation of the underlying concepts. (There are, of course, some | |
| 3332 exceptions.) Also, Unix man pages use a particular format which is | |
| 3333 different from what we use in GNU manuals. | |
| 3334 | |
| 3335 Please include an email address in the manual for where to report | |
| 3336 bugs @emph{in the text of the manual}. | |
| 3337 | |
| 3338 Please do not use the term ``pathname'' that is used in Unix | |
| 3339 documentation; use ``file name'' (two words) instead. We use the term | |
| 3340 ``path'' only for search paths, which are lists of directory names. | |
| 3341 | |
| 3342 Please do not use the term ``illegal'' to refer to erroneous input to | |
| 3343 a computer program. Please use ``invalid'' for this, and reserve the | |
| 3344 term ``illegal'' for activities prohibited by law. | |
| 3345 | |
| 6775 | 3346 Please do not write @samp{()} after a function name just to indicate |
| 3347 it is a function. @code{foo ()} is not a function, it is a function | |
| 3348 call with no arguments. | |
| 3349 | |
| 4958 | 3350 @node Doc Strings and Manuals |
| 3351 @section Doc Strings and Manuals | |
| 3352 | |
| 3353 Some programming systems, such as Emacs, provide a documentation string | |
| 3354 for each function, command or variable. You may be tempted to write a | |
| 3355 reference manual by compiling the documentation strings and writing a | |
| 3356 little additional text to go around them---but you must not do it. That | |
| 3357 approach is a fundamental mistake. The text of well-written | |
| 3358 documentation strings will be entirely wrong for a manual. | |
| 3359 | |
| 3360 A documentation string needs to stand alone---when it appears on the | |
| 3361 screen, there will be no other text to introduce or explain it. | |
| 3362 Meanwhile, it can be rather informal in style. | |
| 3363 | |
| 3364 The text describing a function or variable in a manual must not stand | |
| 3365 alone; it appears in the context of a section or subsection. Other text | |
| 3366 at the beginning of the section should explain some of the concepts, and | |
| 3367 should often make some general points that apply to several functions or | |
| 3368 variables. The previous descriptions of functions and variables in the | |
| 3369 section will also have given information about the topic. A description | |
| 3370 written to stand alone would repeat some of that information; this | |
| 6946 | 3371 redundancy looks bad. Meanwhile, the informality that is acceptable in |
| 4958 | 3372 a documentation string is totally unacceptable in a manual. |
| 3373 | |
| 3374 The only good way to use documentation strings in writing a good manual | |
| 3375 is to use them as a source of information for writing good text. | |
| 3376 | |
| 3377 @node Manual Structure Details | |
| 3378 @section Manual Structure Details | |
| 3379 @cindex manual structure | |
| 3380 | |
| 3381 The title page of the manual should state the version of the programs or | |
| 3382 packages documented in the manual. The Top node of the manual should | |
| 3383 also contain this information. If the manual is changing more | |
| 3384 frequently than or independent of the program, also state a version | |
| 3385 number for the manual in both of these places. | |
| 3386 | |
| 3387 Each program documented in the manual should have a node named | |
| 3388 @samp{@var{program} Invocation} or @samp{Invoking @var{program}}. This | |
| 3389 node (together with its subnodes, if any) should describe the program's | |
| 3390 command line arguments and how to run it (the sort of information people | |
| 5301 | 3391 would look for in a man page). Start with an @samp{@@example} |
| 4958 | 3392 containing a template for all the options and arguments that the program |
| 3393 uses. | |
| 3394 | |
| 3395 Alternatively, put a menu item in some menu whose item name fits one of | |
| 3396 the above patterns. This identifies the node which that item points to | |
| 3397 as the node for this purpose, regardless of the node's actual name. | |
| 3398 | |
| 3399 The @samp{--usage} feature of the Info reader looks for such a node | |
| 3400 or menu item in order to find the relevant text, so it is essential | |
| 3401 for every Texinfo file to have one. | |
| 3402 | |
| 3403 If one manual describes several programs, it should have such a node for | |
| 3404 each program described in the manual. | |
| 3405 | |
| 3406 @node License for Manuals | |
| 3407 @section License for Manuals | |
| 3408 @cindex license for manuals | |
| 3409 | |
| 3410 Please use the GNU Free Documentation License for all GNU manuals that | |
| 3411 are more than a few pages long. Likewise for a collection of short | |
| 3412 documents---you only need one copy of the GNU FDL for the whole | |
| 3413 collection. For a single short document, you can use a very permissive | |
| 3414 non-copyleft license, to avoid taking up space with a long license. | |
| 3415 | |
| 3416 See @uref{http://www.gnu.org/copyleft/fdl-howto.html} for more explanation | |
| 3417 of how to employ the GFDL. | |
| 3418 | |
| 3419 Note that it is not obligatory to include a copy of the GNU GPL or GNU | |
| 3420 LGPL in a manual whose license is neither the GPL nor the LGPL. It can | |
| 3421 be a good idea to include the program's license in a large manual; in a | |
| 3422 short manual, whose size would be increased considerably by including | |
| 3423 the program's license, it is probably better not to include it. | |
| 3424 | |
| 3425 @node Manual Credits | |
| 3426 @section Manual Credits | |
| 3427 @cindex credits for manuals | |
| 3428 | |
| 3429 Please credit the principal human writers of the manual as the authors, | |
| 3430 on the title page of the manual. If a company sponsored the work, thank | |
| 3431 the company in a suitable place in the manual, but do not cite the | |
| 3432 company as an author. | |
| 3433 | |
| 3434 @node Printed Manuals | |
| 3435 @section Printed Manuals | |
| 3436 | |
| 3437 The FSF publishes some GNU manuals in printed form. To encourage sales | |
| 3438 of these manuals, the on-line versions of the manual should mention at | |
| 3439 the very start that the printed manual is available and should point at | |
| 3440 information for getting it---for instance, with a link to the page | |
| 3441 @url{http://www.gnu.org/order/order.html}. This should not be included | |
| 3442 in the printed manual, though, because there it is redundant. | |
| 3443 | |
| 3444 It is also useful to explain in the on-line forms of the manual how the | |
| 3445 user can print out the manual from the sources. | |
| 3446 | |
| 3447 @node NEWS File | |
| 3448 @section The NEWS File | |
| 3449 @cindex @file{NEWS} file | |
| 3450 | |
| 3451 In addition to its manual, the package should have a file named | |
| 3452 @file{NEWS} which contains a list of user-visible changes worth | |
| 3453 mentioning. In each new release, add items to the front of the file and | |
| 3454 identify the version they pertain to. Don't discard old items; leave | |
| 3455 them in the file after the newer items. This way, a user upgrading from | |
| 3456 any previous version can see what is new. | |
| 3457 | |
| 3458 If the @file{NEWS} file gets very long, move some of the older items | |
| 3459 into a file named @file{ONEWS} and put a note at the end referring the | |
| 3460 user to that file. | |
| 3461 | |
| 3462 @node Change Logs | |
| 3463 @section Change Logs | |
| 3464 @cindex change logs | |
| 3465 | |
| 3466 Keep a change log to describe all the changes made to program source | |
| 3467 files. The purpose of this is so that people investigating bugs in the | |
| 3468 future will know about the changes that might have introduced the bug. | |
| 3469 Often a new bug can be found by looking at what was recently changed. | |
| 3470 More importantly, change logs can help you eliminate conceptual | |
| 3471 inconsistencies between different parts of a program, by giving you a | |
| 3472 history of how the conflicting concepts arose and who they came from. | |
| 3473 | |
| 3474 @menu | |
| 6725 | 3475 * Change Log Concepts:: |
| 3476 * Style of Change Logs:: | |
| 3477 * Simple Changes:: | |
| 3478 * Conditional Changes:: | |
| 4958 | 3479 * Indicating the Part Changed:: |
| 3480 @end menu | |
| 3481 | |
| 3482 @node Change Log Concepts | |
| 3483 @subsection Change Log Concepts | |
| 3484 | |
| 3485 You can think of the change log as a conceptual ``undo list'' which | |
| 3486 explains how earlier versions were different from the current version. | |
| 3487 People can see the current version; they don't need the change log | |
| 3488 to tell them what is in it. What they want from a change log is a | |
| 3489 clear explanation of how the earlier version differed. | |
| 3490 | |
| 3491 The change log file is normally called @file{ChangeLog} and covers an | |
| 3492 entire directory. Each directory can have its own change log, or a | |
| 3493 directory can use the change log of its parent directory--it's up to | |
| 3494 you. | |
| 3495 | |
| 3496 Another alternative is to record change log information with a version | |
| 3497 control system such as RCS or CVS. This can be converted automatically | |
| 3498 to a @file{ChangeLog} file using @code{rcs2log}; in Emacs, the command | |
| 3499 @kbd{C-x v a} (@code{vc-update-change-log}) does the job. | |
| 3500 | |
| 3501 There's no need to describe the full purpose of the changes or how they | |
| 3502 work together. If you think that a change calls for explanation, you're | |
| 3503 probably right. Please do explain it---but please put the explanation | |
| 3504 in comments in the code, where people will see it whenever they see the | |
| 3505 code. For example, ``New function'' is enough for the change log when | |
| 3506 you add a function, because there should be a comment before the | |
| 3507 function definition to explain what it does. | |
| 3508 | |
| 3509 In the past, we recommended not mentioning changes in non-software | |
| 3510 files (manuals, help files, etc.) in change logs. However, we've been | |
| 3511 advised that it is a good idea to include them, for the sake of | |
| 3512 copyright records. | |
| 3513 | |
| 3514 However, sometimes it is useful to write one line to describe the | |
| 3515 overall purpose of a batch of changes. | |
| 3516 | |
| 3517 The easiest way to add an entry to @file{ChangeLog} is with the Emacs | |
| 3518 command @kbd{M-x add-change-log-entry}. An entry should have an | |
| 3519 asterisk, the name of the changed file, and then in parentheses the name | |
| 3520 of the changed functions, variables or whatever, followed by a colon. | |
| 3521 Then describe the changes you made to that function or variable. | |
| 3522 | |
| 3523 @node Style of Change Logs | |
| 3524 @subsection Style of Change Logs | |
| 3525 @cindex change logs, style | |
| 3526 | |
| 3527 Here are some simple examples of change log entries, starting with the | |
| 3528 header line that says who made the change and when it was installed, | |
| 3529 followed by descriptions of specific changes. (These examples are | |
| 3530 drawn from Emacs and GCC.) | |
| 3531 | |
| 3532 @example | |
| 3533 1998-08-17 Richard Stallman <rms@@gnu.org> | |
| 3534 | |
| 3535 * register.el (insert-register): Return nil. | |
| 3536 (jump-to-register): Likewise. | |
| 3537 | |
| 3538 * sort.el (sort-subr): Return nil. | |
| 3539 | |
| 3540 * tex-mode.el (tex-bibtex-file, tex-file, tex-region): | |
| 3541 Restart the tex shell if process is gone or stopped. | |
| 3542 (tex-shell-running): New function. | |
| 3543 | |
| 3544 * expr.c (store_one_arg): Round size up for move_block_to_reg. | |
| 3545 (expand_call): Round up when emitting USE insns. | |
| 3546 * stmt.c (assign_parms): Round size up for move_block_from_reg. | |
| 3547 @end example | |
| 3548 | |
| 3549 It's important to name the changed function or variable in full. Don't | |
| 3550 abbreviate function or variable names, and don't combine them. | |
| 3551 Subsequent maintainers will often search for a function name to find all | |
| 3552 the change log entries that pertain to it; if you abbreviate the name, | |
| 3553 they won't find it when they search. | |
| 3554 | |
| 3555 For example, some people are tempted to abbreviate groups of function | |
| 3556 names by writing @samp{* register.el (@{insert,jump-to@}-register)}; | |
| 3557 this is not a good idea, since searching for @code{jump-to-register} or | |
| 3558 @code{insert-register} would not find that entry. | |
| 3559 | |
| 3560 Separate unrelated change log entries with blank lines. When two | |
| 3561 entries represent parts of the same change, so that they work together, | |
| 3562 then don't put blank lines between them. Then you can omit the file | |
| 3563 name and the asterisk when successive entries are in the same file. | |
| 3564 | |
| 3565 Break long lists of function names by closing continued lines with | |
| 3566 @samp{)}, rather than @samp{,}, and opening the continuation with | |
| 3567 @samp{(} as in this example: | |
| 3568 | |
| 3569 @example | |
| 3570 * keyboard.c (menu_bar_items, tool_bar_items) | |
| 3571 (Fexecute_extended_command): Deal with `keymap' property. | |
| 3572 @end example | |
| 3573 | |
| 3574 When you install someone else's changes, put the contributor's name in | |
| 3575 the change log entry rather than in the text of the entry. In other | |
| 3576 words, write this: | |
| 3577 | |
| 3578 @example | |
| 3579 2002-07-14 John Doe <jdoe@@gnu.org> | |
| 3580 | |
| 3581 * sewing.c: Make it sew. | |
| 3582 @end example | |
| 3583 | |
| 3584 @noindent | |
| 3585 rather than this: | |
| 3586 | |
| 3587 @example | |
| 3588 2002-07-14 Usual Maintainer <usual@@gnu.org> | |
| 3589 | |
| 3590 * sewing.c: Make it sew. Patch by jdoe@@gnu.org. | |
| 3591 @end example | |
| 3592 | |
| 3593 As for the date, that should be the date you applied the change. | |
| 3594 | |
| 3595 @node Simple Changes | |
| 3596 @subsection Simple Changes | |
| 3597 | |
| 3598 Certain simple kinds of changes don't need much detail in the change | |
| 3599 log. | |
| 3600 | |
| 3601 When you change the calling sequence of a function in a simple fashion, | |
| 3602 and you change all the callers of the function to use the new calling | |
| 3603 sequence, there is no need to make individual entries for all the | |
| 3604 callers that you changed. Just write in the entry for the function | |
| 3605 being called, ``All callers changed''---like this: | |
| 3606 | |
| 3607 @example | |
| 3608 * keyboard.c (Fcommand_execute): New arg SPECIAL. | |
| 3609 All callers changed. | |
| 3610 @end example | |
| 3611 | |
| 3612 When you change just comments or doc strings, it is enough to write an | |
| 3613 entry for the file, without mentioning the functions. Just ``Doc | |
| 3614 fixes'' is enough for the change log. | |
| 3615 | |
| 3616 There's no technical need to make change log entries for documentation | |
| 3617 files. This is because documentation is not susceptible to bugs that | |
| 3618 are hard to fix. Documentation does not consist of parts that must | |
| 3619 interact in a precisely engineered fashion. To correct an error, you | |
| 3620 need not know the history of the erroneous passage; it is enough to | |
| 3621 compare what the documentation says with the way the program actually | |
| 3622 works. | |
| 3623 | |
| 3624 However, you should keep change logs for documentation files when the | |
| 3625 project gets copyright assignments from its contributors, so as to | |
| 3626 make the records of authorship more accurate. | |
| 3627 | |
| 3628 @node Conditional Changes | |
| 3629 @subsection Conditional Changes | |
| 3630 @cindex conditional changes, and change logs | |
| 3631 @cindex change logs, conditional changes | |
| 3632 | |
| 3633 C programs often contain compile-time @code{#if} conditionals. Many | |
| 3634 changes are conditional; sometimes you add a new definition which is | |
| 3635 entirely contained in a conditional. It is very useful to indicate in | |
| 3636 the change log the conditions for which the change applies. | |
| 3637 | |
| 3638 Our convention for indicating conditional changes is to use square | |
| 3639 brackets around the name of the condition. | |
| 3640 | |
| 3641 Here is a simple example, describing a change which is conditional but | |
| 3642 does not have a function or entity name associated with it: | |
| 3643 | |
| 3644 @example | |
| 3645 * xterm.c [SOLARIS2]: Include string.h. | |
| 3646 @end example | |
| 3647 | |
| 3648 Here is an entry describing a new definition which is entirely | |
| 3649 conditional. This new definition for the macro @code{FRAME_WINDOW_P} is | |
| 3650 used only when @code{HAVE_X_WINDOWS} is defined: | |
| 3651 | |
| 3652 @example | |
| 3653 * frame.h [HAVE_X_WINDOWS] (FRAME_WINDOW_P): Macro defined. | |
| 3654 @end example | |
| 3655 | |
| 3656 Here is an entry for a change within the function @code{init_display}, | |
| 3657 whose definition as a whole is unconditional, but the changes themselves | |
| 3658 are contained in a @samp{#ifdef HAVE_LIBNCURSES} conditional: | |
| 3659 | |
| 3660 @example | |
| 3661 * dispnew.c (init_display) [HAVE_LIBNCURSES]: If X, call tgetent. | |
| 3662 @end example | |
| 3663 | |
| 3664 Here is an entry for a change that takes affect only when | |
| 3665 a certain macro is @emph{not} defined: | |
| 3666 | |
| 3667 @example | |
| 3668 (gethostname) [!HAVE_SOCKETS]: Replace with winsock version. | |
| 3669 @end example | |
| 3670 | |
| 3671 @node Indicating the Part Changed | |
| 3672 @subsection Indicating the Part Changed | |
| 3673 | |
| 3674 Indicate the part of a function which changed by using angle brackets | |
| 3675 enclosing an indication of what the changed part does. Here is an entry | |
| 3676 for a change in the part of the function @code{sh-while-getopts} that | |
| 3677 deals with @code{sh} commands: | |
| 3678 | |
| 3679 @example | |
| 3680 * progmodes/sh-script.el (sh-while-getopts) <sh>: Handle case that | |
| 3681 user-specified option string is empty. | |
| 3682 @end example | |
| 3683 | |
| 3684 | |
| 3685 @node Man Pages | |
| 3686 @section Man Pages | |
| 3687 @cindex man pages | |
| 3688 | |
| 3689 In the GNU project, man pages are secondary. It is not necessary or | |
| 3690 expected for every GNU program to have a man page, but some of them do. | |
| 3691 It's your choice whether to include a man page in your program. | |
| 3692 | |
| 3693 When you make this decision, consider that supporting a man page | |
| 3694 requires continual effort each time the program is changed. The time | |
| 3695 you spend on the man page is time taken away from more useful work. | |
| 3696 | |
| 3697 For a simple program which changes little, updating the man page may be | |
| 3698 a small job. Then there is little reason not to include a man page, if | |
| 3699 you have one. | |
| 3700 | |
| 3701 For a large program that changes a great deal, updating a man page may | |
| 3702 be a substantial burden. If a user offers to donate a man page, you may | |
| 3703 find this gift costly to accept. It may be better to refuse the man | |
| 3704 page unless the same person agrees to take full responsibility for | |
| 3705 maintaining it---so that you can wash your hands of it entirely. If | |
| 3706 this volunteer later ceases to do the job, then don't feel obliged to | |
| 3707 pick it up yourself; it may be better to withdraw the man page from the | |
| 3708 distribution until someone else agrees to update it. | |
| 3709 | |
| 3710 When a program changes only a little, you may feel that the | |
| 3711 discrepancies are small enough that the man page remains useful without | |
| 3712 updating. If so, put a prominent note near the beginning of the man | |
| 3713 page explaining that you don't maintain it and that the Texinfo manual | |
| 3714 is more authoritative. The note should say how to access the Texinfo | |
| 3715 documentation. | |
| 3716 | |
|
5495
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3717 Be sure that man pages include a copyright statement and free |
|
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|
3718 license. The simple all-permissive license is appropriate for simple |
|
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|
3719 man pages: |
|
5fe0551f4ec2
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|
3720 |
|
5fe0551f4ec2
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|
3721 @example |
|
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|
3722 Copying and distribution of this file, with or without modification, |
|
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|
3723 are permitted in any medium without royalty provided the copyright |
|
5fe0551f4ec2
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|
3724 notice and this notice are preserved. |
|
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3725 @end example |
|
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|
3726 |
|
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|
3727 For long man pages, with enough explanation and documentation that |
|
5fe0551f4ec2
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|
3728 they can be considered true manuals, use the GFDL (@pxref{License for |
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|
3729 Manuals}). |
|
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|
3730 |
| 5301 | 3731 Finally, the GNU help2man program |
| 3732 (@uref{http://www.gnu.org/software/help2man/}) is one way to automate | |
| 3733 generation of a man page, in this case from @option{--help} output. | |
| 3734 This is sufficient in many cases. | |
| 3735 | |
| 4958 | 3736 @node Reading other Manuals |
| 3737 @section Reading other Manuals | |
| 3738 | |
| 3739 There may be non-free books or documentation files that describe the | |
| 3740 program you are documenting. | |
| 3741 | |
| 3742 It is ok to use these documents for reference, just as the author of a | |
| 3743 new algebra textbook can read other books on algebra. A large portion | |
| 3744 of any non-fiction book consists of facts, in this case facts about how | |
| 3745 a certain program works, and these facts are necessarily the same for | |
| 3746 everyone who writes about the subject. But be careful not to copy your | |
| 3747 outline structure, wording, tables or examples from preexisting non-free | |
| 3748 documentation. Copying from free documentation may be ok; please check | |
| 3749 with the FSF about the individual case. | |
| 3750 | |
| 3751 @node Managing Releases | |
| 3752 @chapter The Release Process | |
| 3753 @cindex releasing | |
| 3754 | |
| 3755 Making a release is more than just bundling up your source files in a | |
| 3756 tar file and putting it up for FTP. You should set up your software so | |
| 3757 that it can be configured to run on a variety of systems. Your Makefile | |
| 3758 should conform to the GNU standards described below, and your directory | |
| 3759 layout should also conform to the standards discussed below. Doing so | |
| 3760 makes it easy to include your package into the larger framework of | |
| 3761 all GNU software. | |
| 3762 | |
| 3763 @menu | |
| 9115 | 3764 * Configuration:: How configuration of GNU packages should work. |
| 3765 * Makefile Conventions:: Makefile conventions. | |
| 3766 * Releases:: Making releases | |
| 4958 | 3767 @end menu |
| 3768 | |
| 3769 @node Configuration | |
| 3770 @section How Configuration Should Work | |
| 3771 @cindex program configuration | |
| 3772 | |
| 3773 @pindex configure | |
| 3774 Each GNU distribution should come with a shell script named | |
| 3775 @code{configure}. This script is given arguments which describe the | |
| 3776 kind of machine and system you want to compile the program for. | |
| 3777 | |
| 3778 The @code{configure} script must record the configuration options so | |
| 3779 that they affect compilation. | |
| 3780 | |
| 3781 One way to do this is to make a link from a standard name such as | |
| 3782 @file{config.h} to the proper configuration file for the chosen system. | |
| 3783 If you use this technique, the distribution should @emph{not} contain a | |
| 3784 file named @file{config.h}. This is so that people won't be able to | |
| 3785 build the program without configuring it first. | |
| 3786 | |
| 3787 Another thing that @code{configure} can do is to edit the Makefile. If | |
| 3788 you do this, the distribution should @emph{not} contain a file named | |
| 3789 @file{Makefile}. Instead, it should include a file @file{Makefile.in} which | |
| 3790 contains the input used for editing. Once again, this is so that people | |
| 3791 won't be able to build the program without configuring it first. | |
| 3792 | |
| 3793 If @code{configure} does write the @file{Makefile}, then @file{Makefile} | |
| 3794 should have a target named @file{Makefile} which causes @code{configure} | |
| 3795 to be rerun, setting up the same configuration that was set up last | |
| 3796 time. The files that @code{configure} reads should be listed as | |
| 3797 dependencies of @file{Makefile}. | |
| 3798 | |
| 3799 All the files which are output from the @code{configure} script should | |
| 3800 have comments at the beginning explaining that they were generated | |
| 3801 automatically using @code{configure}. This is so that users won't think | |
| 3802 of trying to edit them by hand. | |
| 3803 | |
| 3804 The @code{configure} script should write a file named @file{config.status} | |
| 3805 which describes which configuration options were specified when the | |
| 3806 program was last configured. This file should be a shell script which, | |
| 3807 if run, will recreate the same configuration. | |
| 3808 | |
| 3809 The @code{configure} script should accept an option of the form | |
| 3810 @samp{--srcdir=@var{dirname}} to specify the directory where sources are found | |
| 3811 (if it is not the current directory). This makes it possible to build | |
| 3812 the program in a separate directory, so that the actual source directory | |
| 3813 is not modified. | |
| 3814 | |
| 3815 If the user does not specify @samp{--srcdir}, then @code{configure} should | |
| 3816 check both @file{.} and @file{..} to see if it can find the sources. If | |
| 3817 it finds the sources in one of these places, it should use them from | |
| 3818 there. Otherwise, it should report that it cannot find the sources, and | |
| 3819 should exit with nonzero status. | |
| 3820 | |
| 3821 Usually the easy way to support @samp{--srcdir} is by editing a | |
| 3822 definition of @code{VPATH} into the Makefile. Some rules may need to | |
| 3823 refer explicitly to the specified source directory. To make this | |
| 3824 possible, @code{configure} can add to the Makefile a variable named | |
| 3825 @code{srcdir} whose value is precisely the specified directory. | |
| 3826 | |
| 9740 | 3827 In addition, the @samp{configure} script should take options |
| 3828 corresponding to most of the standard directory variables | |
| 3829 (@pxref{Directory Variables}). Here is the list: | |
| 3830 | |
| 3831 @example | |
| 3832 --prefix --exec-prefix --bindir --sbindir --libexecdir --sysconfdir | |
| 3833 --sharedstatedir --localstatedir --libdir --includedir --oldincludedir | |
| 3834 --datarootdir --datadir --infodir --localedir --mandir --docdir | |
| 3835 --htmldir --dvidir --pdfdir --psdir | |
| 3836 @end example | |
| 3837 | |
| 4958 | 3838 The @code{configure} script should also take an argument which specifies the |
| 3839 type of system to build the program for. This argument should look like | |
| 3840 this: | |
| 3841 | |
| 3842 @example | |
| 3843 @var{cpu}-@var{company}-@var{system} | |
| 3844 @end example | |
| 3845 | |
| 3846 For example, an Athlon-based GNU/Linux system might be | |
| 3847 @samp{i686-pc-linux-gnu}. | |
| 3848 | |
| 3849 The @code{configure} script needs to be able to decode all plausible | |
| 3850 alternatives for how to describe a machine. Thus, | |
| 6066 | 3851 @samp{athlon-pc-gnu/linux} would be a valid alias. There is a shell |
| 3852 script called | |
| 9823 | 3853 @uref{http://git.savannah.gnu.org/@/gitweb/@/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD, |
| 6066 | 3854 @file{config.sub}} that you can use as a subroutine to validate system |
| 3855 types and canonicalize aliases. | |
| 4958 | 3856 |
| 3857 The @code{configure} script should also take the option | |
| 3858 @option{--build=@var{buildtype}}, which should be equivalent to a | |
| 3859 plain @var{buildtype} argument. For example, @samp{configure | |
| 3860 --build=i686-pc-linux-gnu} is equivalent to @samp{configure | |
| 3861 i686-pc-linux-gnu}. When the build type is not specified by an option | |
| 6066 | 3862 or argument, the @code{configure} script should normally guess it using |
| 3863 the shell script | |
| 9823 | 3864 @uref{http://git.savannah.gnu.org/@/gitweb/@/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD, |
| 6066 | 3865 @file{config.guess}}. |
| 4958 | 3866 |
| 3867 @cindex optional features, configure-time | |
| 3868 Other options are permitted to specify in more detail the software | |
| 7159 | 3869 or hardware present on the machine, to include or exclude optional parts |
| 3870 of the package, or to adjust the name of some tools or arguments to them: | |
| 4958 | 3871 |
| 3872 @table @samp | |
| 3873 @item --enable-@var{feature}@r{[}=@var{parameter}@r{]} | |
| 3874 Configure the package to build and install an optional user-level | |
| 3875 facility called @var{feature}. This allows users to choose which | |
| 3876 optional features to include. Giving an optional @var{parameter} of | |
| 3877 @samp{no} should omit @var{feature}, if it is built by default. | |
| 3878 | |
| 3879 No @samp{--enable} option should @strong{ever} cause one feature to | |
| 3880 replace another. No @samp{--enable} option should ever substitute one | |
| 3881 useful behavior for another useful behavior. The only proper use for | |
| 3882 @samp{--enable} is for questions of whether to build part of the program | |
| 3883 or exclude it. | |
| 3884 | |
| 3885 @item --with-@var{package} | |
| 3886 @c @r{[}=@var{parameter}@r{]} | |
| 3887 The package @var{package} will be installed, so configure this package | |
| 3888 to work with @var{package}. | |
| 3889 | |
| 3890 @c Giving an optional @var{parameter} of | |
| 3891 @c @samp{no} should omit @var{package}, if it is used by default. | |
| 3892 | |
| 3893 Possible values of @var{package} include | |
| 3894 @samp{gnu-as} (or @samp{gas}), @samp{gnu-ld}, @samp{gnu-libc}, | |
| 3895 @samp{gdb}, | |
| 3896 @samp{x}, | |
| 3897 and | |
| 3898 @samp{x-toolkit}. | |
| 3899 | |
| 3900 Do not use a @samp{--with} option to specify the file name to use to | |
| 3901 find certain files. That is outside the scope of what @samp{--with} | |
| 3902 options are for. | |
| 7159 | 3903 |
| 3904 @item @var{variable}=@var{value} | |
| 3905 Set the value of the variable @var{variable} to @var{value}. This is | |
| 3906 used to override the default values of commands or arguments in the | |
| 3907 build process. For example, the user could issue @samp{configure | |
| 3908 CFLAGS=-g CXXFLAGS=-g} to build with debugging information and without | |
| 3909 the default optimization. | |
| 3910 | |
| 3911 Specifying variables as arguments to @code{configure}, like this: | |
| 3912 @example | |
| 3913 ./configure CC=gcc | |
| 3914 @end example | |
| 3915 is preferable to setting them in environment variables: | |
| 3916 @example | |
| 3917 CC=gcc ./configure | |
| 3918 @end example | |
| 3919 as it helps to recreate the same configuration later with | |
| 3920 @file{config.status}. | |
| 4958 | 3921 @end table |
| 3922 | |
| 7159 | 3923 All @code{configure} scripts should accept all of the ``detail'' |
| 3924 options and the variable settings, whether or not they make any | |
| 3925 difference to the particular package at hand. In particular, they | |
| 3926 should accept any option that starts with @samp{--with-} or | |
| 3927 @samp{--enable-}. This is so users will be able to configure an | |
| 3928 entire GNU source tree at once with a single set of options. | |
| 4958 | 3929 |
| 3930 You will note that the categories @samp{--with-} and @samp{--enable-} | |
| 3931 are narrow: they @strong{do not} provide a place for any sort of option | |
| 3932 you might think of. That is deliberate. We want to limit the possible | |
| 3933 configuration options in GNU software. We do not want GNU programs to | |
| 3934 have idiosyncratic configuration options. | |
| 3935 | |
| 3936 Packages that perform part of the compilation process may support | |
| 3937 cross-compilation. In such a case, the host and target machines for the | |
| 3938 program may be different. | |
| 3939 | |
| 3940 The @code{configure} script should normally treat the specified type of | |
| 3941 system as both the host and the target, thus producing a program which | |
| 3942 works for the same type of machine that it runs on. | |
| 3943 | |
| 3944 To compile a program to run on a host type that differs from the build | |
| 3945 type, use the configure option @option{--host=@var{hosttype}}, where | |
| 3946 @var{hosttype} uses the same syntax as @var{buildtype}. The host type | |
| 3947 normally defaults to the build type. | |
| 3948 | |
| 3949 To configure a cross-compiler, cross-assembler, or what have you, you | |
| 3950 should specify a target different from the host, using the configure | |
| 3951 option @samp{--target=@var{targettype}}. The syntax for | |
| 3952 @var{targettype} is the same as for the host type. So the command would | |
| 3953 look like this: | |
| 3954 | |
| 3955 @example | |
| 3956 ./configure --host=@var{hosttype} --target=@var{targettype} | |
| 3957 @end example | |
| 3958 | |
| 3959 The target type normally defaults to the host type. | |
| 3960 Programs for which cross-operation is not meaningful need not accept the | |
| 3961 @samp{--target} option, because configuring an entire operating system for | |
| 3962 cross-operation is not a meaningful operation. | |
| 3963 | |
| 3964 Some programs have ways of configuring themselves automatically. If | |
| 3965 your program is set up to do this, your @code{configure} script can simply | |
| 3966 ignore most of its arguments. | |
| 3967 | |
| 3968 @comment The makefile standards are in a separate file that is also | |
| 3969 @comment included by make.texinfo. Done by roland@gnu.ai.mit.edu on 1/6/93. | |
| 3970 @comment For this document, turn chapters into sections, etc. | |
| 3971 @lowersections | |
| 3972 @include make-stds.texi | |
| 3973 @raisesections | |
| 3974 | |
| 3975 @node Releases | |
| 3976 @section Making Releases | |
| 3977 @cindex packaging | |
| 3978 | |
| 3979 You should identify each release with a pair of version numbers, a | |
| 3980 major version and a minor. We have no objection to using more than | |
| 3981 two numbers, but it is very unlikely that you really need them. | |
| 3982 | |
| 3983 Package the distribution of @code{Foo version 69.96} up in a gzipped tar | |
| 3984 file with the name @file{foo-69.96.tar.gz}. It should unpack into a | |
| 3985 subdirectory named @file{foo-69.96}. | |
| 3986 | |
| 3987 Building and installing the program should never modify any of the files | |
| 3988 contained in the distribution. This means that all the files that form | |
| 3989 part of the program in any way must be classified into @dfn{source | |
| 3990 files} and @dfn{non-source files}. Source files are written by humans | |
| 3991 and never changed automatically; non-source files are produced from | |
| 3992 source files by programs under the control of the Makefile. | |
| 3993 | |
| 3994 @cindex @file{README} file | |
| 3995 The distribution should contain a file named @file{README} which gives | |
| 3996 the name of the package, and a general description of what it does. It | |
| 3997 is also good to explain the purpose of each of the first-level | |
| 3998 subdirectories in the package, if there are any. The @file{README} file | |
| 3999 should either state the version number of the package, or refer to where | |
| 4000 in the package it can be found. | |
| 4001 | |
| 4002 The @file{README} file should refer to the file @file{INSTALL}, which | |
| 4003 should contain an explanation of the installation procedure. | |
| 4004 | |
| 4005 The @file{README} file should also refer to the file which contains the | |
| 4006 copying conditions. The GNU GPL, if used, should be in a file called | |
| 4007 @file{COPYING}. If the GNU LGPL is used, it should be in a file called | |
| 4008 @file{COPYING.LIB}. | |
| 4009 | |
| 4010 Naturally, all the source files must be in the distribution. It is okay | |
| 4011 to include non-source files in the distribution, provided they are | |
| 4012 up-to-date and machine-independent, so that building the distribution | |
| 4013 normally will never modify them. We commonly include non-source files | |
| 4014 produced by Bison, @code{lex}, @TeX{}, and @code{makeinfo}; this helps avoid | |
| 4015 unnecessary dependencies between our distributions, so that users can | |
| 4016 install whichever packages they want to install. | |
| 4017 | |
| 4018 Non-source files that might actually be modified by building and | |
| 4019 installing the program should @strong{never} be included in the | |
| 4020 distribution. So if you do distribute non-source files, always make | |
| 4021 sure they are up to date when you make a new distribution. | |
| 4022 | |
| 4023 Make sure that the directory into which the distribution unpacks (as | |
| 4024 well as any subdirectories) are all world-writable (octal mode 777). | |
| 4025 This is so that old versions of @code{tar} which preserve the | |
| 4026 ownership and permissions of the files from the tar archive will be | |
| 4027 able to extract all the files even if the user is unprivileged. | |
| 4028 | |
| 4029 Make sure that all the files in the distribution are world-readable. | |
| 4030 | |
| 4031 Don't include any symbolic links in the distribution itself. If the tar | |
| 4032 file contains symbolic links, then people cannot even unpack it on | |
| 4033 systems that don't support symbolic links. Also, don't use multiple | |
| 4034 names for one file in different directories, because certain file | |
| 4035 systems cannot handle this and that prevents unpacking the | |
| 4036 distribution. | |
| 4037 | |
| 4038 Try to make sure that all the file names will be unique on MS-DOS. A | |
| 4039 name on MS-DOS consists of up to 8 characters, optionally followed by a | |
| 4040 period and up to three characters. MS-DOS will truncate extra | |
| 4041 characters both before and after the period. Thus, | |
| 4042 @file{foobarhacker.c} and @file{foobarhacker.o} are not ambiguous; they | |
| 4043 are truncated to @file{foobarha.c} and @file{foobarha.o}, which are | |
| 4044 distinct. | |
| 4045 | |
| 4046 @cindex @file{texinfo.tex}, in a distribution | |
| 4047 Include in your distribution a copy of the @file{texinfo.tex} you used | |
| 4048 to test print any @file{*.texinfo} or @file{*.texi} files. | |
| 4049 | |
| 4050 Likewise, if your program uses small GNU software packages like regex, | |
| 4051 getopt, obstack, or termcap, include them in the distribution file. | |
| 4052 Leaving them out would make the distribution file a little smaller at | |
| 4053 the expense of possible inconvenience to a user who doesn't know what | |
| 4054 other files to get. | |
| 4055 | |
| 4056 @node References | |
| 4057 @chapter References to Non-Free Software and Documentation | |
| 4058 @cindex references to non-free material | |
| 4059 | |
|
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4060 A GNU program should not recommend, promote, or grant legitimacy to |
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4061 the use of any non-free program. Proprietary software is a social and |
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4062 ethical problem, and our aim is to put an end to that problem. We |
| 4958 | 4063 can't stop some people from writing proprietary programs, or stop |
| 4064 other people from using them, but we can and should refuse to | |
|
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4065 advertise them to new potential customers, or to give the public the |
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4066 idea that their existence is ethical. |
| 4958 | 4067 |
| 5566 | 4068 The GNU definition of free software is found on the GNU web site at |
| 9823 | 4069 @url{http://www.gnu.org/@/philosophy/@/free-sw.html}, and the definition |
| 6537 | 4070 of free documentation is found at |
| 9823 | 4071 @url{http://www.gnu.org/@/philosophy/@/free-doc.html}. The terms ``free'' |
|
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4072 and ``non-free'', used in this document, refer to those definitions. |
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4073 |
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4074 A list of important licenses and whether they qualify as free is in |
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4075 @url{http://www.gnu.org/@/licenses/@/license-list.html}. If it is not |
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4076 clear whether a license qualifies as free, please ask the GNU Project |
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4077 by writing to @email{licensing@@gnu.org}. We will answer, and if the |
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4078 license is an important one, we will add it to the list. |
| 4958 | 4079 |
| 4080 When a non-free program or system is well known, you can mention it in | |
| 4081 passing---that is harmless, since users who might want to use it | |
| 4082 probably already know about it. For instance, it is fine to explain | |
| 4083 how to build your package on top of some widely used non-free | |
| 4084 operating system, or how to use it together with some widely used | |
| 4085 non-free program. | |
| 4086 | |
| 4087 However, you should give only the necessary information to help those | |
| 4088 who already use the non-free program to use your program with | |
| 4089 it---don't give, or refer to, any further information about the | |
| 4090 proprietary program, and don't imply that the proprietary program | |
| 4091 enhances your program, or that its existence is in any way a good | |
| 4092 thing. The goal should be that people already using the proprietary | |
| 4093 program will get the advice they need about how to use your free | |
| 4094 program with it, while people who don't already use the proprietary | |
|
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4095 program will not see anything likely to lead them to take an interest |
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4096 in it. |
| 4958 | 4097 |
| 4098 If a non-free program or system is obscure in your program's domain, | |
| 4099 your program should not mention or support it at all, since doing so | |
| 4100 would tend to popularize the non-free program more than it popularizes | |
|
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4101 your program. (You cannot hope to find many additional users for your |
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4102 program among the users of Foobar, if the existence of Foobar is not |
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4103 generally known among people who might want to use your program.) |
| 4958 | 4104 |
| 4105 Sometimes a program is free software in itself but depends on a | |
| 4106 non-free platform in order to run. For instance, many Java programs | |
|
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4107 depend on some non-free Java libraries. To recommend or promote such |
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4108 a program is to promote the other programs it needs. This is why we |
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4109 are careful about listing Java programs in the Free Software |
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4110 Directory: we don't want to promote the non-free Java libraries. |
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4111 |
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4112 We hope this particular problem with Java will be gone by and by, as |
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4113 we replace the remaining non-free standard Java libraries with free |
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4114 software, but the general principle will remain the same: don't |
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4115 recommend, promote or legitimize programs that depend on non-free |
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4116 software to run. |
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4117 |
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4118 Some free programs strongly encourage the use of non-free software. A |
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4119 typical example is @command{mplayer}. It is free software in itself, |
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4120 and the free code can handle some kinds of files. However, |
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4121 @command{mplayer} recommends use of non-free codecs for other kinds of |
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4122 files, and users that install @command{mplayer} are very likely to |
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4123 install those codecs along with it. To recommend @command{mplayer} |
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4124 is, in effect, to promote use of the non-free codecs. |
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4125 |
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4126 Thus, you should not recommend programs that strongly encourage the |
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4127 use of non-free software. This is why we do not list |
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4128 @command{mplayer} in the Free Software Directory. |
| 4958 | 4129 |
| 4130 A GNU package should not refer the user to any non-free documentation | |
| 4131 for free software. Free documentation that can be included in free | |
| 4132 operating systems is essential for completing the GNU system, or any | |
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4133 free operating system, so encouraging it is a priority; to recommend |
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4134 use of documentation that we are not allowed to include undermines the |
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4135 impetus for the community to produce documentation that we can |
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4136 include. So GNU packages should never recommend non-free |
| 4958 | 4137 documentation. |
| 4138 | |
| 4139 By contrast, it is ok to refer to journal articles and textbooks in | |
| 4140 the comments of a program for explanation of how it functions, even | |
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4141 though they are non-free. This is because we don't include such |
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4142 things in the GNU system even they are free---they are outside the |
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4143 scope of what a software distribution needs to include. |
| 4958 | 4144 |
| 4145 Referring to a web site that describes or recommends a non-free | |
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4146 program is promoting that program, so please do not make links (or |
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4147 mention by name) web sites that contain such material. This policy is |
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4148 relevant particularly for the web pages for a GNU package. |
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4149 |
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4150 Following links from nearly any web site can lead eventually to |
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4151 non-free software; this is inherent in the nature of the web. So it |
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4152 makes no sense to criticize a site for having such links. As long as |
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4153 the site does not itself recommend a non-free program, there is no |
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4154 need to consider the question of the sites that it links to for other |
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4155 reasons. |
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4156 |
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4157 Thus, for example, you should not refer to AT&T's web site if that |
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4158 recommends AT&T's non-free software packages; you should not refer to |
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4159 a site that links to AT&T's site presenting it as a place to get some |
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4160 non-free program, because that link recommends and legitimizes the |
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4161 non-free program. However, that a site contains a link to AT&T's web |
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4162 site for some other purpose (such as long-distance telephone service) |
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4163 is not an objection against it. |
| 9115 | 4164 |
| 4165 @node GNU Free Documentation License | |
| 4166 @appendix GNU Free Documentation License | |
| 4167 | |
| 4168 @cindex FDL, GNU Free Documentation License | |
| 4958 | 4169 @include fdl.texi |
| 4170 | |
| 4171 @node Index | |
| 4172 @unnumbered Index | |
| 4173 @printindex cp | |
| 4174 | |
| 4175 @bye | |
| 4176 | |
| 4177 Local variables: | |
| 4178 eval: (add-hook 'write-file-hooks 'time-stamp) | |
| 4179 time-stamp-start: "@set lastupdate " | |
| 4180 time-stamp-end: "$" | |
| 4181 time-stamp-format: "%:b %:d, %:y" | |
| 4182 compile-command: "make just-standards" | |
| 4183 End: |