Hello:
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
You will see that $_error is printed before sleep is called, which
would seem
to mean that the contents of $_error would be sent back before the
sleep cycle
started. But it is printed to the browser window after the delay. The
out put
shown in the browser is at the end. So how would I actually test
flock? It
does not seem to be blocking the second query. (Maybe I have
misunderstood
the reason for it).
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
Thanks for time and attention
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