posix_spawn_file_actions_addchdir: New module. Suggested by Eric Blake in <https://lists.gnu.org/archive/html/bug-findutils/2018-09/msg00007.html>. * lib/spawn.in.h (posix_spawn_file_actions_addchdir): New declaration. * lib/spawn_int.h (struct __spawn_action): Add tag 'spawn_do_chdir' and union member 'chdir_action'. * lib/spawn_faction_addchdir.c: New file. * lib/spawni.c (__spawni): Implement the spawn_do_chdir action. * lib/spawn_faction_addclose.c: Test REPLACE_POSIX_SPAWN instead of HAVE_WORKING_POSIX_SPAWN. * lib/spawn_faction_adddup2.c: Likewise. * lib/spawn_faction_addopen.c: Likewise. * m4/posix_spawn_faction_addchdir.m4: New file. * m4/posix_spawn.m4 (gl_POSIX_SPAWN_BODY): Test whether module 'posix_spawn_file_actions_addchdir' is present and whether posix_spawn_file_actions_addchdir_np exists. Define REPLACE_POSIX_SPAWN instead of HAVE_WORKING_POSIX_SPAWN. * m4/spawn_h.m4 (gl_SPAWN_H): Test whether posix_spawn_file_actions_addchdir is declared. (gl_SPAWN_H_DEFAULTS): Initialize GNULIB_POSIX_SPAWN_FILE_ACTIONS_ADDCHDIR, HAVE_POSIX_SPAWN_FILE_ACTIONS_ADDCHDIR, REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDCHDIR. * modules/spawn (Makefile.am): Substitute GNULIB_POSIX_SPAWN_FILE_ACTIONS_ADDCHDIR, HAVE_POSIX_SPAWN_FILE_ACTIONS_ADDCHDIR, REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDCHDIR. * modules/posix_spawn_file_actions_addchdir: New file. * modules/posix_spawn_file_actions_addclose (Depends-on, configure.ac): Test also REPLACE_POSIX_SPAWN. * modules/posix_spawn_file_actions_adddup2 (Depends-on, configure.ac): Likewise. * modules/posix_spawn_file_actions_addopen (Depends-on, configure.ac): Likewise. * tests/test-spawn-c++.cc (posix_spawn_file_actions_addchdir): Check signature. * doc/posix-functions/posix_spawn.texi: Mention the new module. * doc/posix-functions/posix_spawnp.texi: Likewise.

@node posix_spawn
@section @code{posix_spawn}
@findex posix_spawn

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

Gnulib module: posix_spawn

Portability problems fixed by Gnulib:
@itemize
@item
This function is missing on some platforms:
Mac OS X 10.4, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 9, Cygwin, mingw, MSVC 14, Interix 3.5, BeOS, Android 8.1.
@item
When this function fails, it causes the stdio buffer contents to be output
twice on some platforms:
AIX 6.1.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
This function does not work on some platforms:
AIX 6.1 (under particular circumstances), mingw.
@end itemize

The Gnulib module @code{posix_spawn_file_actions_addchdir} provides an
additional action, that consists in changing the current directory of
the child process before starting the specified program.