Re: Behavior of the sleep function?

Jeffry Killen wrote: > I am experimenting with flock to find out how it works. > > I set up a page with a form that uses javascript ajax async 'get' > to query the server. > > The reason for using ajax is that the page will not reload so > I can keep a count of the queries issued and simulate two different > users trying to edit the file. > > I am assuming that the first query (which calls flock and invokes the > sleep function) > would block the second query. > > But the second query succeeds and the the first query returns after 10 > seconds > > Here is the code: > > <?php > > $_jsTest = ''; > $_error = ''; > if(!is_file('lab6_target.txt')) > { > if(is_writeable('./')) > { > $_fw = fopen('lab6_target.txt', 'w'); > fwrite($_fw, "some bs text for the sake of testing this turkey."); > fclose($_fw); > } > } > if($_GET) > { > if($_GET['tstNo'] == '1') > { > $_jsTest = $_GET['tst1']; > $_fw = fopen('lab6_target.txt', 'a'); > flock($_fw, LOCK_EX); // LOCK_SH, LOCK_EX, LOCK_UN > $_error = "starting 10 second sleep"; > header('Content-Type: text/plain'); > print $_error; > sleep(10); > fwrite($_fw, $_GET['tst1']); > flock($_fw, LOCK_UN); > fclose($_fw); > exit; > } > else if($_GET['tstNo'] == '2') > { > $_jsTest = $_GET['tst1']; > $_fw = fopen('lab6_target.txt', 'a'); > if(!$_fw) > { > header('Content-Type: text/plain'); > print "file not opened for write on second test"; > exit; > } > else > { > fwrite($_fw, $_GET['tst1']); > fclose($_fw); > header('Content-Type: text/plain'); > print "success"; > exit; > } > } > } > ?> > > Test Result: successstarting 10 second sleep flock() implements *advisory* file locking, i.e. it works only if *all* file accesses use flock() to probe for a lock. So, basically, you have to call flock($_fw, LOCK_EX) also for $_GET['tstNo'] == '2'. -- Christoph M. Becker