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]

In reply to Re^3: Mechanism for ensuring only one instance of a Perl script can only run? by Corion
in thread Mechanism for ensuring only one instance of a Perl script can only run? by redapplesonly

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.