Improve popen compatibility with glibc.
* libc/posix/popen.c (popen): The 2006-08-22 change to use FD_CLOEXEC disagrees with other implementations; instead, use pidlist to work even when fcntl is not available. Meanwhile, support the 'e' modifier to set CLOEXEC, as in glibc. Drop cygwin-specific code, now that cygwin has its own version. * libc/posix/Makefile.am (CHEWOUT_FILES): Document popen. * libc/posix/posix.tex: New file.
This commit is contained in:
Eric Blake
parent
56dbf99329
commit
a051160962
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@ -1,3 +1,14 @@
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2009-08-18 Eric Blake <ebb9@byu.net>
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Improve popen compatibility with glibc.
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* libc/posix/popen.c (popen): The 2006-08-22 change to use
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FD_CLOEXEC disagrees with other implementations; instead, use
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pidlist to work even when fcntl is not available. Meanwhile,
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support the 'e' modifier to set CLOEXEC, as in glibc. Drop
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cygwin-specific code, now that cygwin has its own version.
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* libc/posix/Makefile.am (CHEWOUT_FILES): Document popen.
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* libc/posix/posix.tex: New file.
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2009-08-17 Craig Howland <howland@LGSInnovations.com>
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* libc/string/wcsncpy.c (wcsncpy): Re-write function based on small
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@ -51,7 +51,8 @@ endif # USE_LIBTOOL
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include $(srcdir)/../../Makefile.shared
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CHEWOUT_FILES =
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CHEWOUT_FILES = \
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popen.def
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SUFFIXES = .def
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@ -63,8 +64,8 @@ CHEW = ../../doc/makedoc -f $(srcdir)/../../doc/doc.str
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TARGETDOC = ../tmp.texi
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# No doc for posix.
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doc:
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doc: $(CHEWOUT_FILES)
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cat $(srcdir)/posix.tex >> $(TARGETDOC)
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AM_CFLAGS = -D_GNU_SOURCE
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@ -32,6 +32,53 @@
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* SUCH DAMAGE.
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*/
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/*
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FUNCTION
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<<popen>>, <<pclose>>---tie a stream to a command string
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INDEX
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popen
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INDEX
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pclose
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ANSI_SYNOPSIS
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#include <stdio.h>
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FILE *popen(char *<[s]>, char *<[mode]>);
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int pclose(FILE *<[f]>);
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DESCRIPTION
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Use <<popen>> to create a stream to a child process executing a
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command string <<*<[s]>>> as processed by <</bin/sh>> on your system.
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The argument <[mode]> must start with either `<<r>>', where the stream
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reads from the child's <<stdout>>, or `<<w>>', where the stream writes
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to the child's <<stdin>>. As an extension, <[mode]> may also contain
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`<<e>>' to set the close-on-exec bit of the parent's file descriptor.
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The stream created by <<popen>> must be closed by <<pclose>> to avoid
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resource leaks.
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Streams created by prior calls to <<popen>> are not visible in
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subsequent <<popen>> children, regardless of the close-on-exec bit.
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Use ``<<system(NULL)>>'' to test whether your system has <</bin/sh>>
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available.
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RETURNS
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<<popen>> returns a file stream opened with the specified <[mode]>,
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or <<NULL>> if a child process could not be created. <<pclose>>
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returns -1 if the stream was not created by <<popen>> or if the
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application used <<wait>> or similar to steal the status; otherwise
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it returns the exit status of the child which can be interpreted
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in the same manner as a status obtained by <<waitpid>>.
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PORTABILITY
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POSIX.2 requires <<popen>> and <<pclose>>, but only specifies a mode
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of just <<r>> or <<w>>. Where <<sh>> is found is left unspecified.
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Supporting OS subroutines required: <<_exit>>, <<_execve>>, <<_fork_r>>,
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<<_wait_r>>, <<pipe>>, <<fcntl>>, <<sbrk>>.
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*/
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#ifndef _NO_POPEN
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#if defined(LIBC_SCCS) && !defined(lint)
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@ -59,21 +106,21 @@ static struct pid {
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struct pid *next;
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FILE *fp;
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pid_t pid;
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} *pidlist;
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} *pidlist;
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FILE *
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_DEFUN(popen, (program, type),
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const char *program _AND
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const char *type)
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{
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struct pid *cur;
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struct pid *cur, *last;
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FILE *iop;
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int pdes[2], pid;
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if ((*type != 'r' && *type != 'w')
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|| (type[1]
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#ifdef __CYGWIN__
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&& (type[2] || (type[1] != 'b' && type[1] != 't'))
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#ifdef HAVE_FCNTL
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&& (type[2] || (type[1] != 'e'))
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#endif
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)) {
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errno = EINVAL;
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@ -111,12 +158,11 @@ _DEFUN(popen, (program, type),
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}
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(void)close(pdes[1]);
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}
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/* Close all fd's created by prior popen. */
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for (last = NULL, cur = pidlist; cur;
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last = cur, cur = cur->next)
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(void)close (fileno (cur->fp));
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execl(_PATH_BSHELL, "sh", "-c", program, NULL);
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#ifdef __CYGWIN__
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/* On cygwin32, we may not have /bin/sh. In that
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case, try to find sh on PATH. */
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execlp("sh", "sh", "-c", program, NULL);
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#endif
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_exit(127);
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/* NOTREACHED */
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}
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@ -131,9 +177,10 @@ _DEFUN(popen, (program, type),
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}
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#ifdef HAVE_FCNTL
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/* Hide pipe from future popens; assume fcntl can't fail. */
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fcntl (fileno (iop), F_SETFD,
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fcntl (fileno (iop), F_GETFD, 0) | FD_CLOEXEC);
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/* Mark pipe cloexec if requested. */
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if (type[1] == 'e')
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fcntl (fileno (iop), F_SETFD,
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fcntl (fileno (iop), F_GETFD, 0) | FD_CLOEXEC);
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#endif /* HAVE_FCNTL */
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/* Link into list of file descriptors. */
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@ -177,7 +224,7 @@ _DEFUN(pclose, (iop),
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else
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last->next = cur->next;
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free(cur);
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return (pid == -1 ? -1 : pstat);
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}
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@ -0,0 +1,13 @@
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@node Posix
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@chapter Posix Functions
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This chapter groups several utility functions specified by POSIX, but
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not by C. Each function documents which header to use.
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@menu
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* popen:: Create a stream tied to a child process
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@end menu
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@page
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@include posix/popen.def
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