#50177 [Opn]: flock: Example 1 - file is truncated twice

ID: 50177 User updated by: chris at beckr dot org -Summary: Example 1 - file is truncated twice Reported By: chris at beckr dot org Status: Open Bug Type: Documentation problem Operating System: Mac / Linux PHP Version: Irrelevant New Comment: Added 'flock' to title Previous Comments: ------------------------------------------------------------------------ [2009-11-14 22:02:49] chris at beckr dot org Description: ------------ Example 1 of the flock function documentation shows how to lock a file for writing. Once the lock has been obtained, the file is ftruncate()d and date is written. However, the file is opened using "w", which means that the file will already be truncated even before the lock is issued, which means that any readers (LOCK_SH) that validly obtain a lock in the meantime will see an empty file. Using "r+" instead of "w", everything works as expected. Reproduced on OS X (HFS+) and Linux (ext3). Reproduce code: --------------- --- From manual page: function.flock#Examples --- A sample reader counterpart: <?php while (true) { $fp = fopen("/tmp/lock.txt", "r"); if (flock($fp, LOCK_SH)) { // open for reading $contents = ''; while (!feof($fp)) { $contents .= fread($fp, 8192); } echo($contents); flock($fp, LOCK_UN); // release the lock } else { echo "Couldn't get the lock!"; } fclose($fp); } ?> Expected result: ---------------- The reader should print only lines with "Write something here" Actual result: -------------- The reader sometimes prints empty lines ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=50177&edit=1