Jedna instancja cronjob-a

Problem stary jak świat...
Proste rozwiązanie: http://timkay.com/solo/

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#!/usr/bin/perl -s # # solo v1.6 # Prevents multiple cron instances from running simultaneously. # # Copyright 2007-2013 Timothy Kay # http://timkay.com/solo/ # # It is free software; you can redistribute it and/or modify it under the terms of either: # # a) the GNU General Public License as published by the Free Software Foundation; #    either version 1 (http://dev.perl.org/licenses/gpl1.html), or (at your option) #    any later version (http://www.fsf.org/licenses/licenses.html#GNUGPL), or # # b) the "Artistic License" (http://dev.perl.org/licenses/artistic.html), or # # c) the MIT License (http://opensource.org/licenses/MIT) #   use Socket;   alarm $timeout        if $timeout;   $port =~ /^\d+$/ or $noport      or die "Usage: $0 -port=PORT COMMAND\n";   if ($port) {     $addr = pack(CnC, 127, $<, 1);     print "solo: bind ", join(".", unpack(C4, $addr)), ":$port\n" if $verbose;       $^F = 10;   # unset close-on-exec       socket(SOLO, PF_INET, SOCK_STREAM, getprotobyname('tcp'))  or die "socket: $!";     bind(SOLO, sockaddr_in($port, $addr))    or $silent? exit: die "solo($port): $!\n"; }   sleep $sleep if $sleep;   exec @ARGV;