Re^2: Mechanism for ensuring only one instance of a Perl script can only run?

Thanks Corion! So one caveat I have is that if a newly-executed script realizes that there's another instance already at work, I want the new script to terminate immediately, not enter a queue to run later. It looks like flock() doesn't offer a "terminate immediately" option... or am I missing the bigger picture. Thank you so much for writing.

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Re^3: Mechanism for ensuring only one instance of a Perl script can only run? by Corion (Patriarch) on Dec 02, 2022 at 17:43 UTC
No. flock returns a false value if it cannot lock a file because it is already locked. The idea is that you then exit your program: `use Fcntl qw(LOCK_EX LOCK_NB); my $scriptname = $0; # assuming that all script instances will be invo +ked the same way open my $script, $scriptname or die "Couldn't find myself?! Looked for '$script', but got $!"; if( !flock $script, LOCK_EX \| LOCK_NB ) { print "We are already running\n"; exit 1; }; sleep 60` [download]	[reply] [d/l]

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Re^3: Mechanism for ensuring only one instance of a Perl script can only run?
by Corion (Patriarch) on Dec 02, 2022 at 17:43 UTC

No. flock returns a false value if it cannot lock a file because it is already locked. The idea is that you then exit your program:

use Fcntl qw(LOCK_EX LOCK_NB);
my $scriptname = $0; # assuming that all script instances will be invo
+ked the same way

open my $script, $scriptname
    or die "Couldn't find myself?! Looked for '$script', but got $!";
if( !flock $script, LOCK_EX | LOCK_NB ) {
    print "We are already running\n";
    exit 1;
};

sleep 60
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