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#!/usr/bin/perl
# Minimal Daemon (c) 2011 Paul Buetow
use strict;
use warnings;
use POSIX qw(setsid);
$| = 1;
sub trimstr (@) {
my @str = @_;
for (@str) {
chomp;
s/^[\t\s]+//;
s/[\t\s]+$//;
}
return @str;
}
sub trunc ($) {
my $file = shift;
open my $fh, ">$file" or die "Can't write $file: $!\n";
print $fh '';
close $fh;
}
sub logmsg ($$) {
my ($config, $msg) = @_;
my $logfile = $config->{'daemon.logfile'};
open my $fh, ">>$logfile" or die "Can't write logfile $logfile: $!\n";
print $fh localtime()." (PID $$): $msg\n";
close $fh;
}
sub err ($$) {
my ($config, $msg) = @_;
logmsg $config => $msg;
die "$msg\n";
}
sub checkpid ($) {
my $config = shift;
my $pidfile = $config->{'daemon.pidfile'};
trunc $pidfile unless -f $pidfile;
open my $fh, $pidfile or err $config => "Can't read pidfile $pidfile: $!";
my ($pid) = <$fh>;
close $fh;
if (defined $pid) {
chomp $pid;
err $config => "Process with pid $pid already running" if 0 < int $pid && kill 0, $pid;
}
}
sub writepid ($) {
my $config = shift;
my $pidfile = $config->{'daemon.pidfile'};
open my $fh, ">$pidfile" or err $config => "Can't write pidfile: $!";
print $fh "$$\n";
close $fh;
}
sub readconfig ($) {
my $configfile = shift;
open my $fh, $configfile or die "Can't read $configfile\n";
my %config;
while (<$fh>) {
next if /^[\t\w]+#/;
s/#.*//;
my ($key, $val) = trimstr split '=', $_, 2;
next unless defined $val;
$config{$key} = $val;
}
close $fh;
# Check
my $msg = 'Missing property:';
foreach (qw(wd pidfile logfile truncatelog version)) {
my $key = "daemon.$_";
die "$msg $key\n" unless exists $config{$key};
}
logmsg \%config => "Reading $configfile complete";
return \%config;
}
sub daemonize ($) {
my $config = shift;
logmsg $config => 'Daemonizing...';
chdir $config->{'daemon.wd'} or err $config => "Can't chdir to wd: $!";
my $msg = 'Can\'t read /dev/null:';
open STDIN, '>/dev/null' or err $config => "$msg $!";
open STDOUT, '>/dev/null' or err $config => "$msg $!";
open STDERR, '>/dev/null' or err $config => "$msg $!";
defined (my $pid = fork) or err $config => "Can't fork: $!";
exit if $pid;
setsid or err $config => "Can't start a new session: $!";
writepid $config;
logmsg $config => 'Daemonizing completed';
}
sub prestartup ($) {
my $config = shift;
checkpid $config;
trunc $config->{'daemon.logfile'} if $config->{'daemon.truncatelog'} eq 'yes';
}
sub daemonloop ($) {
my $config = shift;
my $loop = shift;
for (my $i = 1;;++$i) {
logmsg $config => $config->{'daemon.version'} . ": Hello $i";
sleep 3;
}
}
my $config = readconfig shift;
prestartup $config;
daemonize $config;
daemonloop $config;
|
