Here is a daemon that does the right things: 

#!/usr/bin/perl -w

$|++;
use strict;
use Fcntl;
use POSIX qw(setsid);
my ($PROGRAM) = $0 =~ m!([^\\/:]+)$!;
my $LOCKFILE = "/var/lock/$PROGRAM";
my $LOG      = "/var/log/$PROGRAM.error.log";


# use a lockfile to prevent spawning duplicate processes
unless ( sysopen(my $fh, $LOCKFILE, O_CREAT | O_EXCL | O_RDWR, 0600) )
+ {
    # the lockfile already exists
    print "Lockfile $LOCKFILE aready exists.\nChecking for running $PR
+OGRAM process...";
    my @ps = grep{ m/\Q$PROGRAM\E/ } `ps -C $PROGRAM`;
    # we expect 1 copy (us) running
    # print "@ps\n";
    die "\nThere is already a copy of $PROGRAM running!\n" if @ps > 1;
    print "None!\n";
}

# now demonize it

defined(my $pid = fork)   or die "Can't fork: $!";
exit 0 if $pid;

chdir '/'                 or die "Can't chdir to /: $!";
umask 0;
setsid()                  or die "Can't start a new session: $!";

$SIG{INT} = $SIG{TERM} = sub { 
    unlink $LOCKFILE or warn "Could not unlink $LOCKFILE for $PROGRAM\
+n"; 
    exit; 
};

$SIG{HUP} = sub { 
    warn "Caught HUP " . time() . "\n"; 
    # do reset stuff if required
};

print "Started $0 daemon OK\n\n";

open STDIN, '/dev/null'   or die "Can't read /dev/null: $!";
open STDOUT, '>/dev/null' or die "Can't write to /dev/null: $!";
#open STDERR, '>/dev/null' or die "Can't write to /dev/null: $!";
open STDERR, ">>$LOG" or die "Can't write to $LOG: $!";


# this is the main loop that runs forever, once every 30 seconds

while (1) {
    eval{ ... };   # use eval to exec any code so if it chokes the dae
+mon survives
    warn "$@\n" if $@;
    sleep 30;
}

[download]

cheers

tachyon

In reply to Re: fork process + SIG handlers by tachyon
in thread fork process + SIG handlers by cidaris

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