1 files changed, 49 insertions, 0 deletions
diff --git a/lib/fd-safer.c b/lib/fd-safer.c
new file mode 100644
index 0000000..e011c00
--- /dev/null
+++ b/lib/fd-safer.c
@@ -0,0 +1,49 @@
+/* Return a safer copy of a file descriptor.
+
+   Copyright (C) 2005-2006, 2009-2020 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 3 of the License, 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, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Paul Eggert.  */
+
+#include <config.h>
+
+#include "unistd-safer.h"
+
+#include <errno.h>
+#include <unistd.h>
+
+/* Return FD, unless FD would be a copy of standard input, output, or
+   error; in that case, return a duplicate of FD, closing FD.  On
+   failure to duplicate, close FD, set errno, and return -1.  Preserve
+   errno if FD is negative, so that the caller can always inspect
+   errno when the returned value is negative.
+
+   This function is usefully wrapped around functions that return file
+   descriptors, e.g., fd_safer (open ("file", O_RDONLY)).  */
+
+int
+fd_safer (int fd)
+{
+  if (STDIN_FILENO <= fd && fd <= STDERR_FILENO)
+    {
+      int f = dup_safer (fd);
+      int e = errno;
+      close (fd);
+      errno = e;
+      fd = f;
+    }
+
+  return fd;
+}