If I don't want the processes to block, then would the only changes I needed to make be in

resulting in the code below (rev. of previous code)? Are there any other obvious problems (that might lead to race conditions, for example) in the code below?

I actually don't want the extraneous ones to block, but to go ahead and exit, because other instances can pick up and process waiting data later-I just don't want to slam the machine with a huge number of processes doing heavy processing at once. 

#!/usr/bin/perl -w

use strict;

use IPC::SysV qw(IPC_PRIVATE S_IRWXU IPC_CREAT SEM_UNDO ftok);
use IPC::Semaphore;

srand;

my $sem =
  new IPC::Semaphore( ftok( $0, 0 ), 1, S_IRWXU | IPC_CREAT );

my $semval = $sem->getval(0);
$semval = 0 unless ( defined($semval) );

exit(0) if ( $semval >= 10 );
$sem->op( 0, 1, SEM_UNDO );

#
# Do work... or in this case, 
# print the value of $semval and sleep for a while
#
print $semval + 1, "\n";
sleep( int( rand(20) + 1 ) );

#
# Decrement the semaphore value
#
$semval = $sem->getval(0);
if ($semval) {
    $sem->op( 0, -1, SEM_UNDO );
}
else {
    $sem->remove;
}
__END__
#
# Sample test execution (in bash):
#
# index=500
# while [ $index -gt 0 ] 
# do 
#     perl test.pl & 
#     let "index=index-1" 
# done
#

[download]

In reply to Re^2: Effective use of IPC::Semaphore to limit number of concurrent executions of a scxipt by atcroft
in thread Effective use of IPC::Semaphore to limit number of concurrent executions of a scxipt by atcroft

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.