Rewritten by Paul Eggert.

Now, the minimum overhead is just two system calls: dup and close.

diff --git a/lib/stdopen.c b/lib/stdopen.c
index 6cf52189660604f07c05615c156f4b7b98778183..2bf2a01b4316d7ef86cd276d1505067ebebc0ad4 100644 (file)
--- a/lib/stdopen.c
+++ b/lib/stdopen.c
@@ -1,6 +1,24 @@
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <fcntl.h>
+#if HAVE_FCNTL_H
+# include <fcntl.h>
+#endif
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+#include <errno.h>
+
+#ifndef STDIN_FILENO
+# define STDIN_FILENO 0
+#endif
+
+#ifndef STDOUT_FILENO
+# define STDOUT_FILENO 1
+#endif
+
+#ifndef STDERR_FILENO
+# define STDERR_FILENO 2
+#endif
 
 /* Try to ensure that each of the standard file numbers (0, 1, 2)
    is in use.  Without this, each application would have to guard
@@ -9,23 +27,19 @@
 void
 stdopen (void)
 {
-  int fd;
-  for (fd = 0; fd <= 2; fd++)
+  int fd = dup (STDIN_FILENO);
+
+  if (0 <= fd)
+    close (fd);
+  else if (errno == EBADF)
+    fd = open ("/dev/null", O_WRONLY);
+
+  if (STDIN_FILENO <= fd && fd <= STDERR_FILENO)
     {
-      struct stat sb;
-      if (fstat (fd, &sb) < 0)
-       {
-         static const int flag[] = { O_WRONLY, O_RDONLY, O_RDONLY };
-         /* FIXME: worry about errno != EBADF?  */
-         char const *file = "/dev/null";
-         int fd2 = open (file, flag[fd]);
-         if (fd2 < 0)
-           break;
-         if (fd2 != fd)
-           {
-             close (fd2);
-             break;
-           }
-       }
+      fd = open ("/dev/null", O_RDONLY);
+      if (fd == STDOUT_FILENO)
+       fd = dup (fd);
+      if (STDERR_FILENO < fd)
+       close (fd);
     }
 }