flock()

[Anon]

In the documentation is written:
"If you don't want flock() to block while locking, add 4 to operation. "
Does it mean that I must use:

$fd=fopen($filename,"w+") or die("Can't open $filename");
flock($fd, 2);
$written4=fwrite($fd,$data);
flock($fd, 4);
fclose($fd);

instead of

$fd=fopen($filename,"w+") or die("Can't open $filename");
flock($fd, 2);
$written4=fwrite($fd,$data);
flock($fd, 3);
fclose($fd);

And must I lock files that I open only for reading with fread($fd,filesize($filename))?

Thank you

vlad

[kparker]

"add 4" means just that:

flock( $fd, 2+4);

will give the same lock mode as flock(...,2) except that it will not block if the file can't be locked. But this further means you can't just write code like you would if it were blocking. From your example:

$fd=fopen($filename,"w+") or die("Can't open $filename");
flock($fd, 6);
$written4=fwrite($fd,$data);

This usage is ineffective, since you go ahead and write to the file regardless of whether or not the lock was obtained.

As in any case of non-blocking calls, you only want to use it if you are going to be polling somehow.

[Anon]

thanks