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-rw-r--r--m4/isapipe.m493
1 files changed, 93 insertions, 0 deletions
diff --git a/m4/isapipe.m4 b/m4/isapipe.m4
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+++ b/m4/isapipe.m4
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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
+])