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tools/sctk-2.4.10/src/sclite/readpipe.c
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/* Open a pipe to read from a program without intermediary sh.
Copyright (C) 1992 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
/* Written by David MacKenzie. */
/* modified the non-ANSI C definitions of readpipe so as to compile */
/* on an AIX system -Jon Fiscus */
#include <sctk.h>
#if HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdio.h>
#if __STDC__
#include <stdarg.h>
#else
#include <varargs.h>
#endif
#if HAVE_UNISTD_H
# include <unistd.h>
#endif
/* Open a pipe to read from a program without intermediary sh. Checks
PATH. Sample use:
stream = readpipe ("progname", "arg1", "arg2", (char *) 0);
Return 0 on error. */
#if __STDC__
FILE *
readpipe (char *progname, ...)
#else
FILE *
readpipe (va_alist)
va_dcl
#endif
{
#if DIFF_ENABLED
#if ! __STDC__
char *progname;
#endif
int fds[2];
va_list ap;
char *args[100];
int argno = 0;
/* Copy arguments into `args'. */
#if __STDC__
va_start (ap, progname);
#else
va_start (ap);
progname = va_arg (ap, char *);
#endif
args[argno++] = progname;
while ((args[argno++] = va_arg (ap, char *)) != NULL)
;
va_end (ap);
if (pipe (fds) == -1)
return 0;
switch (fork ())
{
case 0: /* Child. Write to pipe. */
close (fds[0]); /* Not needed. */
if (fds[1] != 1) /* Redirect 1 (stdout) only if needed. */
{
close (1); /* We don't want the old stdout. */
if (dup (fds[1]) == 0)/* Maybe stdin was closed. */
{
dup (fds[1]); /* Guaranteed to dup to 1 (stdout). */
close (0);
}
close (fds[1]); /* No longer needed. */
}
execvp (args[0], args);
_exit (2); /* 2 for `cmp'. */
case -1: /* Error. */
return 0;
default: /* Parent. Read from pipe. */
close (fds[1]); /* Not needed. */
return (FILE *)fdopen (fds[0], "r");
}
#else
return 0;
#endif /* #if DIFF_ENABLED */
}
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