Support non-blocking pipe I/O in read() on native Windows. * lib/unistd.in.h: Include <sys/types.h> also for 'read'. (read): New declaration. * lib/read.c: New file. * lib/stdio.in.h (_GL_ATTRIBUTE_FORMAT_SCANF, _GL_ATTRIBUTE_FORMAT_SCANF_SYSTEM): New macros. (fgetc, fgets, fread, fscanf, getc, getchar, gets, scanf, vfscanf, vscanf): New declarations. * lib/stdio-read.c: New file. * m4/read.m4: New file. * m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Initialize GNULIB_READ, REPLACE_READ. * m4/stdio_h.m4 (gl_STDIO_H): Set GNULIB_FGETC, GNULIB_FGETS, GNULIB_FREAD, GNULIB_FSCANF, GNULIB_GETC, GNULIB_GETCHAR, GNULIB_GETS, GNULIB_SCANF, GNULIB_VFSCANF, GNULIB_VSCANF. In non-blocking I/O is desired and needs workarounds, set REPLACE_STDIO_READ_FUNCS. (gl_STDIO_H_DEFAULTS): Initialize GNULIB_FGETC, GNULIB_FGETS, GNULIB_FREAD, GNULIB_FSCANF, GNULIB_GETC, GNULIB_GETCHAR, GNULIB_GETS, GNULIB_SCANF, GNULIB_VFSCANF, GNULIB_VSCANF, REPLACE_STDIO_READ_FUNCS. * modules/read: New file. * modules/nonblocking (Files): Add lib/stdio-read.c. * modules/unistd (Makefile.am): Substitute GNULIB_READ, REPLACE_READ. * modules/stdio (Makefile.am): Substitute GNULIB_FGETC, GNULIB_FGETS, GNULIB_FREAD, GNULIB_FSCANF, GNULIB_GETC, GNULIB_GETCHAR, GNULIB_GETS, GNULIB_SCANF, GNULIB_VFSCANF, GNULIB_VSCANF, REPLACE_STDIO_READ_FUNCS. * modules/pread (Depends-on): Add read. * modules/safe-read (Depends-on): Likewise. * tests/test-stdio-c++.cc (fgetc, fgets, fread, fscanf, getc, getchar, gets, scanf, vfscanf, vscanf): Verify signatures. * doc/posix-functions/read.texi: Mention 'nonblocking' module and problem with non-blocking pipes. * doc/posix-functions/fgetc.texi: Likewise. * doc/posix-functions/fgets.texi: Likewise. * doc/posix-functions/fread.texi: Likewise. * doc/posix-functions/fscanf.texi: Likewise. * doc/posix-functions/getc.texi: Likewise. * doc/posix-functions/getchar.texi: Likewise. * doc/posix-functions/gets.texi: Likewise. * doc/posix-functions/scanf.texi: Likewise. * doc/posix-functions/vfscanf.texi: Likewise. * doc/posix-functions/vscanf.texi: Likewise.

@node fgetc
@section @code{fgetc}
@findex fgetc

POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/fgetc.html}

Gnulib module: stdio, nonblocking

Portability problems fixed by Gnulib module @code{stdio}, together with module @code{nonblocking}:
@itemize
@item
When reading from a non-blocking pipe whose buffer is empty, this function
fails with @code{errno} being set to @code{EINVAL} instead of @code{EAGAIN} on
some platforms:
mingw.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
On Windows platforms (excluding Cygwin), this function does not set @code{errno}
upon failure.
@end itemize