A short while ago Bart Lateur was kind enough to help me improve the method I
use for locking files. The routine he sent me is below (I have commented it
heavily to help me follow it, and used my own error reporting routine):
__SNIP__
use Fcntl;
my @lockfiles;
my $timeOut = 10;
END {
for ( @lock_files ) { unlink }
}
sub lockFile {
# Create a lock file for the file passed as a parameter.
# If no parameter is passed, return a false value.
my $lock_file = shift() . '.lock';
my $idle = time;
local *LOCK;
# Now try and create a lock file. Try every 1/10th of a second if a file
already exists
until ( sysopen LOCK, $lock_file, O_CREAT|O_TRUNC|O_EXCL|O_WRONLY ) {
# Die if the file cannot be created within a specified time
&outputError( 'Could not create a lock file within the time limit',
$!) if
time - $idle > $timeOut;
# sleep for 1/10th of a second
select undef, undef, undef, 0.1;
}
# If we get here, then the lock file has been created successfully.
# Add the lockfile name to the list to be deleted.
push @lock_files, $lock_file;
# Now send some data to the lock file (anything will do).
print LOCK $$;
close LOCK;
return 1;
}
__END_SNIP__
I have just implemented this routine, and it works very well. Many thanks to
Bart. However, I am a little unsure about what to do if the script cannot
create a lock file within the prescribed time (in this case 10 seconds). I do
not want visitors to be faced with a dead script if a lock file is left on the
server for any reason. If possible, can anyone advise me of any method that I
can safely use to remove this file?
Any help would be much appreciated.
TIA,
Richard
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