On Mon, Mar 18, 2002 at 03:57:55AM -0500, Mark-Jason Dominus wrote:
> Actually that reminds me of another puzzle I have. My module provides
> an interface to 'flock'. What is an easy way to check that the file
> is actually being locked? I put off writing the tests because i did
> not want to fork.
I just thought of a clever way to do it without alarm! Just use
non-blocking mode.
lock_file($foo);
open(FH, $foo);
ok( !flock(FH, LOCK_NB | LOCK_EX) );
if the flock fails the file is already locked.
The traditional approaches require causing a deadlock and breaking it
with alarm.
my $start = time;
lock_file($foo);
eval {
local $SIG{ALRM} = sub { die "ALARM!\n" };
alarm 5;
lock_file($foo);
alarm 0;
};
is( $@, "ALARM\n" );
can_ok( time, '>', $start + 3, 'Locking works' );
I check both the time and the alarm for thoroughness. I have had a
few issues with this on 5.6.0 where, for some odd reason, everything
dies correctly but the "ALARM!\n" message goes to STDERR and not to
$@. I can't duplicate it outside the context of a single program, so
you might be safe.
So here's the other way. We cause a deadlock using another process
which kills itself after a certain amount of time.
my $start = time;
lock_file($foo);
system($^X, '-e', 'use Whatever; alarm 5; lock_file($foo)');
cmp_ok( time, '>', $start + 3, 'Locking works' );
again, these all rely on alarm().
> Is this mailing list the right place to ask "how do I test for X"
> questions? Or would the module-authors list be more appropriate?
This is the right place. I'm keeping track of the questions &
answers, someday there will be a FAQ.
--
Michael G. Schwern <[EMAIL PROTECTED]> http://www.pobox.com/~schwern/
Perl Quality Assurance <[EMAIL PROTECTED]> Kwalitee Is Job One
My lips, your breast and a whole lotta strange arguing.
