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Posted by Steve Buehler on 10/03/28 11:10
At 03:14 PM 3/10/2005, Richard Lynch wrote:
> > I want to read a number from an external (txt) file and increment it.then
> > save the number back on the text file.
> > I know this is possible but want a simple amd economical way to do this.
>
>That's what you *THINK* you want to do :-)
>
>But what happens when *TWO* users hit that same script at exactly the same
>time.
Richard has a good idea about using mysql to do this. Some things I have
not tried, but might also do for you is php's flock
http://www.php.net/flock . Or go to http://www.php.net/fopen and search
the page for "lock" (no quotes). The example you might want was the 4th
instance of that word that I found.
<?php
#going to update last users counter script since
#aborting a write because a file is locked is not correct.
$counter_file = '/tmp/counter.txt';
clearstatcache();
ignore_user_abort(true); ## prevent refresh from aborting file operations
and hosing file
if (file_exists($counter_file)) {
$fh = fopen($counter_file, 'r+');
while(1) {
if (flock($fh, LOCK_EX)) {
#$buffer = chop(fgets($fh, 2));
$buffer = chop(fread($fh, filesize($counter_file)));
$buffer++;
rewind($fh);
fwrite($fh, $buffer);
fflush($fh);
ftruncate($fh, ftell($fh));
flock($fh, LOCK_UN);
break;
}
}
}
else {
$fh = fopen($counter_file, 'w+');
fwrite($fh, "1");
$buffer="1";
}
fclose($fh);
print "Count is $buffer";
?>
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