* MODULES.html.sh (File system functions): New module write-any-file.

[gnulib.git] / lib / write-any-file.c

diff --git a/lib/write-any-file.c b/lib/write-any-file.c
new file mode 100644 (file)
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--- /dev/null
+++ b/lib/write-any-file.c
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+/* Determine whether we can write any file.
+
+   Copyright (C) 2007 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 2, 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, write to the Free Software Foundation,
+   Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by Paul Eggert.  */
+
+#include <config.h>
+
+#include "write-any-file.h"
+
+#if HAVE_PRIV_H
+# include <priv.h>
+#endif
+#include <unistd.h>
+
+/* Return true if we know that we can write any file, including
+   writing directories.  */
+
+bool
+can_write_any_file (void)
+{
+  static bool initialized;
+  static bool can;
+
+  if (! initialized)
+    {
+#if defined PRIV_EFFECTIVE && defined PRIV_FILE_DAC_WRITE
+      priv_set_t *pset = priv_allocset ();
+      if (pset)
+       {
+         can =
+           (getppriv (PRIV_EFFECTIVE, pset) == 0
+            && priv_ismember (pset, PRIV_FILE_DAC_WRITE));
+         priv_freeset (pset);
+       }
+      else
+#else
+      /* In traditional Unix, only root can unlink directories.  */
+      can = (geteuid () == 0);
+#endif
+      initialized = true;
+    }
+
+  return can;
+}