pfSense

/****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;

}