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Daemon::Generic(3pm) User Contributed Perl Documentation Daemon::Generic(3pm)


 Daemon::Generic - framework to provide start/stop/reload for a daemon


 use Daemon::Generic;
 sub gd_run { ... stuff }


Daemon::Generic provides a framework for starting, stopping, reconfiguring daemon-like programs. The framework provides for standard commands that work for as init.d files and as apachectl-like commands.

Programs that use Daemon::Generic subclass Daemon::Generic to override its behavior. Almost everything that Genric::Daemon does can be overridden as needed.


Unless overridden, the usage output for your program will look something like this:

 Usage: $progname [ -c file ] [ -f ] { start | stop | reload | restart | help | version | check }
  -c            Specify configuration file (defaults to $configfile)
  -f            Run in the foreground (don't detach)
  start         Starts a new $progname if there isn't one running already
  stop          Stops a running $progname
  reload        Causes a running $progname to reload it's config file.  Starts
                a new one if none is running.
  restart       Stops a running $progname if one is running.  Starts a new one.
  check         Check the configuration file and report the daemon state
  help          Display this usage info
  version       Display the version of $progname


To hand control over to "Daemon::Generic", call "newdaemon()". Control will be handed back through method calls to functions you define.

Your @ISA will be modified to include "Daemon::Generic" if if it isn't already there.

These are the arguments to "newdaemon()". Defaults are in (parenthesis).

($0) The name of this program. This will be used for logging and for naming the PID file.
("/etc/$progname.conf") The location of the configuration file for this daemon.
(/var/run/$progname) We include the configuration file name as part of the pid file in case there are multiple instances of this daemon. The pidbase is the part of the PID file that does not include the configuration file name.
("$pidbase.$") The location of the process id file.
(0) Do not detach/daemon and run in the foreground instead.
(0) Turn on debugging.
(0) Normall srand() is called. If no_srand is set then srand() won't be called.
() Additional arguments for Getopt::Long::GetOptions which is used to parse @ARGV. Alternatively: define "&gd_more_opt()".
(1) Minimum number of @ARGV arguments after flags have been processed.
(1) Maximum number of @ARGV arguments after flags have been processed.
($pkg::VERSION) The version number of the daemon.
Used for "logger -p".


The package that subclasses Daemon::Generic must provide the following callback methods.

This is where you put your main program.

It is okay to change userid/group as the first action of gd_run().


The package that subclasses Daemon::Generic does not have to override these methods but it may want to.

"gd_preconfig()" is called to parse the configuration file ("$self->{configfile}"). Preconfig is called on all invocations of the daemon ("daemon reload", "daemon check", "daemon stop", etc). It shouldn't start anything but it can and should verify that the config file is fine.

The return value should be a hash. With one exception, the return value is only used by "gd_postconfig()". The exception is that "gd_preconfig()" may return a revised PID file location (key "pidfile").

Most uses of Daemon::Generic should define "gd_preconfig".

Postconfig() is called only when the daemon is actually starting up. (Or on reconfigs). It is passed the return value from "gd_preconfig".
Set things up so that SIGHUP calls gd_reconfig_event() and SIGINT calls gd_quit_event(). It will call these at any time so if you want to delay signal delivery or something you should override this method.
This is invoked to parse the command line. Useful things to modify are:
The location of the configuration file to be parsed by "gd_preconfig()".
Run in the foreground (don't daemonize).
Use it yourself.

The supplied "gd_getopt()" method uses Getopt::Long.

Parse any additional command line arguments beyond what "gd_getopt()" handled.

$ARGV[0] needs to be left alone if it is one of the following standard items:

Start up a new daemon.
Stop the running daemon.
Stop the running daemon, start a new one.
Send a signal to the running daemon, asking it to reconfigure itself.
Just check the configuration file.
Print the help screen (probably usage()).
Display the daemon's version.

There is no default "gd_parse_argv()".

Normal behavior: return. Define additional checks to run when the "check" command is given. A $pid will only be supplied if there is a daemon running.
Normal behavior: display a version message and exit.
Normal behavior: call "gd_usage()".
Used by "gd_usage()": provide information on additional commands beyond "start", "stop", "reload", etc. Return is an array of key value pairs.

 sub gd_commands_more 
        return (
                savestate => 'Tell xyz server to save its state',
                reset     => 'Tell xyz servr to reset',
Like "gd_commands_more()" but defines additional command line flags. There should also be a "gd_more_opt()" or an "options" argument to "new()".
Like "gd_commands_more()" but defines positional arguments.
Display a usage message. The return value from "gd_usage()" is the exit code for the program.
() Additional arguments for Getopt::Long::GetOptions which is used to parse @ARGV. Alternatively: pass "options" to "new()".
Figure out the PID file should be.
Print out an error (call die?)
Called $ARGV[0] isn't one of the commands that Daemon::Generic knows by default. Default behavior: call "gd_usage()" and exit(1).
Normal behavior: "fork()", "fork()", detach from tty.
This is a mis-named method. Sorry. This directs "STDOUT"/"STDERR"/"STDIN" to "/dev/null" as part of daemonizing. Used by "gd_daemonize()".
After daemonizing, output file descriptors are be re-established. Normal behavior: redirect "STDOUT" and "STDERR" to "logger -t $progname[$$]". Used by "gd_daemonize()".
Normal behavior: $progname[$$]. Used by "gd_redirect_output()".
Normal behavior: call "gd_postconfig(gd_preconfig))". Only referenced by "gd_setup_signals()".
Normal behavior: exit. Only referenced by "gd_setup_signals()".
Return true if gd_kill should kill process groups ($pid) instead of just the one daemon ($pid). Default is false.
Used by the "stop" and "restart" commands to get rid of the old daemon. Normal behavior: send a SIGINT. Check to see if process $pid has died. If it has not, keep checking and if it's still alive. After $Daemon::Generic::force_quit_delay seconds, send a SIGTERM. Keep checking. After another $Daemon::Generic::force_quit_delay seconds, send a SIGKILL (-9). Keep checking. After "$Daemon::Generic::force_quit_delay * 4" seconds or 60 seconds (whichever is smaller), give up and exit(1).
Installs the daemon so that it runs automatically at next reboot. Currently done with a symlink to $0 and "/usr/sbin/update-rc.d". Please send patches for other methods!
Returns a function to do an "gd_install" if installation is possible. Returns 0 otherwise.
Normal behavior: return. Called just before doing an installation. The method indicates the installation method (currently always "update-rc.d".)
Normal behavior: return. Called just after doing an installation.
Will remove the daemon from the automatic startup regime.
Returns a function to do the work for "gd_uninstall" if it's possible. 0 otherwise.
Normal behavior: return. Called just before doing an un-installation. The method indicates the installation method (currently always "update-rc.d".)
Normal behavior: return. Called just after doing an un-installation.


Since you need to subclass Daemon::Generic, you need to know what the internal data structures for Daemon::Generic are. With two exceptions, all of the member data items begin with the prefix "gd_".

The location of the configuration file. (Not used by Daemon::Generic).
Display debugging? (Not used by Daemon::Generic)
The original %args passed to "new".
The process name. (defaults to $0)
The location of the process ID file.
Used for "logger -p".
Are we running in the foreground?


 my $sleeptime = 1;
        progname        => 'ticktockd',
        pidfile         => '/var/run/',
        configfile      => '/etc/ticktockd.conf',
 sub gd_preconfig
        my ($self) = @_;
        open(CONFIG, "<$self->{configfile}") or die;
        while(<CONFIG>) {
                $sleeptime = $1 if /^sleeptime\s+(\d+)/;
        return ();
 sub gd_run
        while(1) {
                print scalar(localtime(time))."\n";


With a while(1) and delayed signal delivery: Daemon::Generic::While1.

With Event: Daemon::Generic::Event.

With AnyEvent: Daemon::Generic::AnyEvent.

Modules that use Daemon::Generic: SyslogScan::Daemon; IO::Event (

Other modules that do similar things: Net::Daemon, Net::Server, Net::Server::Daemonize, NetServer::Generic, Proc::Application::Daemon, Proc::Daemon, Proc::Forking.


Copyright (C) 2006-2010 David Muir Sharnoff <>. Copyright (C) 2011 Google, Inc. This module may be used and distributed on the same terms as Perl itself.


Daemon::Generic is packaged for Fedora by Emmanuel Seyman <>.

2022-06-12 perl v5.34.0