Help with fwrite()

Hi all, Im trying to delete a line from a file after having first read the line. The file contains a list or urls, one per new line: like this: urls.txt http://example.com/somedir/ http://www.example.com/page.php?name=Nick+W Here's what I have so far: <?php $file = 'urls.txt'; $f = fopen($file, 'r+'); $url2use = fgets($f); fseek($f, 0); fwrite($f, '', strlen($url2use)); // Where is the "gotha"? print($url2use); fclose($f); ?> Clearly im using fwrite incorrectly (at least i think that's clear ;-) but i cant seem to figure out what im doing wrong? (well, i kinda can but i cant get any further with it without a little help..) Much thanks for your time... -- Nick W