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# Test whether a file descriptor is a pipe.
dnl Copyright (C) 2006, 2009-2022 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
dnl Written by Paul Eggert.
AC_DEFUN([gl_ISAPIPE],
[
# OpenVMS has isapipe already, so check for it.
AC_CHECK_FUNCS([isapipe])
if test $ac_cv_func_isapipe = yes; then
HAVE_ISAPIPE=1
else
HAVE_ISAPIPE=0
fi
])
# Prerequisites of lib/isapipe.c.
AC_DEFUN([gl_PREREQ_ISAPIPE],
[
AC_CACHE_CHECK([whether pipes are FIFOs (and for their link count)],
[gl_cv_pipes_are_fifos],
[AC_RUN_IFELSE(
[AC_LANG_SOURCE(
[[#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#ifndef S_ISFIFO
#define S_ISFIFO(m) 0
#endif
#ifndef S_ISSOCK
#define S_ISSOCK(m) 0
#endif
int
main (int argc, char **argv)
{
int fd[2];
struct stat st;
if (pipe (fd) != 0)
return 1;
if (fstat (fd[0], &st) != 0)
return 2;
if (2 <= argc && argv[1][0] == '-')
{
char const *yesno = (S_ISFIFO (st.st_mode) ? "yes" : "no");
if (st.st_nlink <= 1)
{
long int i = st.st_nlink;
if (i != st.st_nlink)
return 3;
printf ("%s (%ld)\n", yesno, i);
}
else
{
unsigned long int i = st.st_nlink;
if (i != st.st_nlink)
return 4;
printf ("%s (%lu)\n", yesno, i);
}
}
else
{
if (! S_ISFIFO (st.st_mode) && ! S_ISSOCK (st.st_mode))
return 5;
}
return 0;
}]])],
[gl_cv_pipes_are_fifos=`./conftest$ac_exeext -`
test -z "$gl_cv_pipes_are_fifos" && gl_cv_pipes_are_fifos=no],
[gl_cv_pipes_are_fifos=unknown],
[gl_cv_pipes_are_fifos=cross-compiling])])
case $gl_cv_pipes_are_fifos in #(
'yes ('*')')
AC_DEFINE([HAVE_FIFO_PIPES], [1],
[Define to 1 if pipes are FIFOs, 0 if sockets. Leave undefined
if not known.]);; #(
'no ('*')')
AC_DEFINE([HAVE_FIFO_PIPES], [0]);;
esac
case $gl_cv_pipes_are_fifos in #(
*'('*')')
AC_DEFINE_UNQUOTED([PIPE_LINK_COUNT_MAX],
[`expr "$gl_cv_pipes_are_fifos" : '.*\((.*)\)'`],
[Define to the maximum link count that a true pipe can have.]);;
esac
])
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