MFC of changeset [22584]

Atomic file writing
Patch-by: David Rees

1 files changed, 40 insertions, 0 deletions

diff --git a/etc/inc/pfsense-utils.inc b/etc/inc/pfsense-utils.inc
index 7c92560..47854d5 100644
--- a/etc/inc/pfsense-utils.inc
+++ b/etc/inc/pfsense-utils.inc
@@ -3621,4 +3621,44 @@ function is_wan_interface_up($interface) {
 	return false;
 }
 
+/****f* pfsense-utils/safe_write_file
+ * NAME
+ *   safe_write_file - Write a file out atomically
+ * DESCRIPTION
+ *   safe_write_file() Writes a file out atomically by first writing to a
+ *   temporary file of the same name but ending with the pid of the current
+ *   process, them renaming the temporary file over the original.
+ * INPUTS
+ *   $filename  - string containing the filename of the file to write
+ *   $content   - string containing the file content to write to file
+ *   $force_binary      - boolean denoting whether we should force binary
+ *   mode writing.
+ * RESULT
+ *   boolean - true if successful, false if not
+ ******/
+function safe_write_file($file, $content, $force_binary) {
+        $tmp_file = $file . "." . getmypid();
+        $write_mode = $force_binary ? "wb" : "w";
+
+        $fd = fopen($tmp_file, $write_mode);
+        if (!$fd) {
+                // Unable to open temporary file for writing
+                return false;
+        }
+        if (!fwrite($fd, $content)) {
+                // Unable to write to temporary file
+                fclose($fd);
+                return false;
+        }
+        fclose($fd);
+
+        if (!rename($tmp_file, $file)) {
+                // Unable to move temporary file to original
+                unlink($tmp_file);
+                return false;
+        }
+        return true;
+}
+
+
 ?>