* modules/isapipe: New file.

[gnulib.git] / m4 / isapipe.m4

diff --git a/m4/isapipe.m4 b/m4/isapipe.m4
new file mode 100644 (file)
index 0000000..04e6934
--- /dev/null
+++ b/m4/isapipe.m4
@@ -0,0 +1,89 @@
+# Test whether a file descriptor is a pipe.
+
+dnl Copyright (C) 2006 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_REPLACE_FUNCS(isapipe)
+  if test $ac_cv_func_isapipe = no; then
+    gl_PREREQ_ISAPIPE
+  fi
+])
+
+# Prerequisites of lib/isapipe.c.
+AC_DEFUN([gl_PREREQ_ISAPIPE],
+[
+  AC_CACHE_CHECK([whether pipes are FIFOs (and for their link count)],
+    [gl_cv_pipes_are_fifos],
+    [AC_RUN_IFELSE(
+       [AC_LANG_SOURCE(
+         [[#include <stdio.h>
+           #include <sys/types.h>
+           #include <sys/stat.h>
+           #include <unistd.h>
+           #ifndef S_ISFIFO
+            #define S_ISFIFO(m) 0
+           #endif
+           #ifndef S_ISSOCK
+            #define S_ISSOCK(m) 0
+           #endif
+           int
+           main (int argc, char **argv)
+           {
+             int fd[2];
+             struct stat st;
+             if (pipe (fd) != 0 || fstat (fd[0], &st) != 0)
+               return 1;
+             if (2 <= argc && argv[1][0] == '-')
+               {
+                 char const *yesno = (S_ISFIFO (st.st_mode) ? "yes" : "no");
+                 if (st.st_nlink <= 1)
+                   {
+                     long int i = st.st_nlink;
+                     if (i != st.st_nlink)
+                       return 1;
+                     printf ("%s (%ld)\n", yesno, i);
+                   }
+                 else
+                   {
+                     unsigned long int i = st.st_nlink;
+                     if (i != st.st_nlink)
+                       return 1;
+                     printf ("%s (%lu)\n", yesno, i);
+                   }
+               }
+             else
+               {
+                 if (! S_ISFIFO (st.st_mode) && ! S_ISSOCK (st.st_mode))
+                   return 1;
+               }
+             return 0;
+           }]])],
+       [gl_cv_pipes_are_fifos=`./conftest$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
+])