Provided by: libproc-daemon-perl_0.14-1_all bug

NAME

       Proc::Daemon - Run Perl program(s) as a daemon process.

SYNOPSIS

           use Proc::Daemon;

           $daemon = Proc::Daemon->new(
               work_dir => '/my/daemon/directory',
               .....
           );

           $Kid_1_PID = $daemon->Init;

           unless ( $Kid_1_PID ) {
               # code executed only by the child ...
           }

           $Kid_2_PID = $daemon->Init( {
                           work_dir     => '/other/daemon/directory',
                           exec_command => 'perl /home/my_script.pl',
                        } );

           $pid = $daemon->Status( ... );

           $stopped = $daemon->Kill_Daemon( ... );

DESCRIPTION

       This module can be used by a Perl program to initialize itself as a daemon or to execute
       ("exec") a system command as daemon. You can also check the status of the daemon (alive or
       dead) and you can kill the daemon.

       A daemon is a process that runs in the background with no controlling terminal. Generally
       servers (like FTP, HTTP and SIP servers) run as daemon processes. Do not make the mistake
       to think that a daemon is a server. ;-)

       Proc::Daemon does the following:

       1.  The script forks a child.

       2.  The child changes the current working directory to the value of 'work_dir'.

       3.  The child clears the file creation mask.

       4.  The child becomes a session leader, which detaches the program from the controlling
           terminal.

       5.  The child forks another child (the final daemon process). This prevents the potential
           of acquiring a controlling terminal at all and detaches the daemon completely from the
           first parent.

       6.  The second child closes all open file descriptors (unless you define "dont_close_fh"
           and/or "dont_close_fd").

       7.  The second child opens STDIN, STDOUT and STDERR to the location defined in the
           constructor ("new").

       8.  The second child returns to the calling script, or the program defined in
           'exec_command' is executed and the second child never returns.

       9.  The first child transfers the PID of the second child (daemon) to the parent.
           Additionally the PID of the daemon process can be written into a file if 'pid_file' is
           defined. Then the first child exits.

       10. If the parent script is looking for a return value, then the PID(s) of the child/ren
           will be returned. Otherwise the parent will exit.

       NOTE: Because of the second fork the daemon will not be a session-leader and therefore
       Signals will not be send to other members of his process group. If you need the
       functionality of a session-leader you may want to call POSIX::setsid() manually at your
       daemon.

       INFO: Since "fork" is not performed the same way on Windows systems as on Linux, this
       module does not work with Windows. Patches appreciated!

CONSTRUCTOR

       new ( %ARGS )
           The constructor creates a new Proc::Daemon object based on the hash %ARGS. The
           following keys from %ARGS are used:

           work_dir
                   Defines the path to the working directory of your daemon. Defaults to "/".

           setuid  Sets the real user identifier ($<) and the effective user identifier ($>) for
                   the daemon process using "POSIX::setuid( ... )", in case you want to run your
                   daemon under a different user from the parent. Obviously the first user must
                   have the rights to switch to the new user otherwise it will stay the same. It
                   is helpful to define the argument "setuid" if you start your script at boot
                   time by init with the superuser, but wants the daemon to run under a normal
                   user account.

           child_STDIN
                   Defines the path to STDIN for your daemon. Defaults to "/dev/null". Default
                   Mode is '<' (read). You can define other Mode the same way as you do using
                   Perls "open" in a two-argument form.

           child_STDOUT
                   Defines the path where the output of your daemon will go. Defaults to
                   "/dev/null". Default Mode is '+>' (write/read). You can define other Mode the
                   same way as you do using Perls "open" in a two-argument form.

           child_STDERR
                   Defines the path where the error output of your daemon will go. Defaults to
                   "/dev/null". Default Mode is '+>' (write/read). You can define other Mode the
                   same way as you do using Perls "open" in a two-argument form, see example
                   below.

           dont_close_fh
                   If you define it, it must be an arrayref with file handles you want to
                   preserve from the parent into the child (daemon). This may be the case if you
                   have code below a "__DATA__" token in your script or module called by "use" or
                   "require".

                       dont_close_fh => [ 'main::DATA', 'PackageName::DATA', $my_filehandle, ... ],

                   You can add any kind of file handle to the array (expression in single quotes
                   or a scalar variable), including 'STDIN', 'STDOUT' and 'STDERR'. Logically the
                   path settings from above ("child_STDIN", ...) will be ignored in this case.

                   DISCLAIMER: Using this argument may not detach your daemon fully from the
                   parent! Use it at your own risk.

           dont_close_fd
                   Same function and disclaimer as "dont_close_fh", but instead of file handles
                   you write the numeric file descriptors inside the arrayref.

           pid_file
                   Defines the path to a file (owned by the parent user) where the PID of the
                   daemon process will be stored. Defaults to "undef" (= write no file).

           exec_command
                   Scalar or arrayref with system command(s) that will be executed by the daemon
                   via Perls "exec PROGRAM_LIST". In this case the child will never return to the
                   parents process!

           Example:

               my $daemon = Proc::Daemon->new(
                   work_dir     => '/working/daemon/directory',
                   child_STDOUT => '/path/to/daemon/output.file',
                   child_STDERR => '+>>debug.txt',
                   pid_file     => 'pid.txt',
                   exec_command => 'perl /home/my_script.pl',
                 # or:
                 # exec_command => [ 'perl /home/my_script.pl', 'perl /home/my_other_script.pl' ],
               );

           In this example:

           ·       the PID of the daemon will be returned to $daemon in the parent process and a
                   pid-file will be created at "/working/daemon/directory/pid.txt".

           ·       STDOUT will be open with Mode '+>' (write/read) to
                   "/path/to/daemon/output.file" and STDERR will be open to
                   "/working/daemon/directory/debug.txt" with Mode '+>>' (write/read opened for
                   appending).

           ·       the script "/home/my_script.pl" will be executed by "perl" and run as daemon.
                   Therefore the child process will never return to this parent script.

METHODS

       Init( [ { %ARGS } ] )
           Become a daemon.

           If used for the first time after "new", you call "Init" with the object reference to
           start the daemon.

               $pid = $daemon->Init();

           If you want to use the object reference created by "new" for other daemons, you write
           "Init( { %ARGS } )". %ARGS are the same as described in "new". Notice that you
           shouldn't call "Init()" without argument in this case, or the next daemon will execute
           and/or write in the same files as the first daemon. To prevent this use at least an
           empty anonymous hash here.

               $pid = $daemon->Init( {} );
               @pid = $daemon->Init( {
                   work_dir     => '/other/daemon/directory',
                   exec_command => [ 'perl /home/my_second_script.pl', 'perl /home/my_third_script.pl' ],
               } );

           If you don't need the Proc::Daemon object reference in your script, you can also use
           the method without object reference:

               $pid = Proc::Daemon::Init();
               # or
               $pid = Proc::Daemon::Init( { %ARGS } );

           "Init" returns the PID (scalar) of the daemon to the parent, or the PIDs (array) of
           the daemons created if "exec_command" has more then one program to execute. See
           examples above.

           "Init" returns 0 to the child (daemon).

           If you call the "Init" method in the context without looking for a return value (void
           context) the parent process will "exit" here like in earlier versions:

               Proc::Daemon::Init();

       Status( [ $ARG ] )
           This function checks the status of the process (daemon). Returns the PID number
           (alive) or 0 (dead).

           $ARG can be a string with:

           ·       "undef", in this case it tries to get the PID to check out of the object
                   reference settings.

           ·       a PID number to check.

           ·       the path to a file containing the PID to check.

           ·       the command line entry of the running program to check. This requires
                   Proc::ProcessTable to be installed.

       Kill_Daemon( [ $ARG [, SIGNAL] ] )
           This function kills the Daemon process. Returns the number of processes successfully
           killed (which mostly is not the same as the PID number), or 0 if the process wasn't
           found.

           $ARG is the same as of "Status()". SIGNAL is an optional signal name or number as
           required by Perls "kill" function and listed out by "kill -l" on your system. Default
           value is 9 ('KILL' = non-catchable, non-ignorable kill).

       Fork
           Is like the Perl built-in "fork", but it retries to fork over 30 seconds if necessary
           and if possible to fork at all. It returns the child PID to the parent process and 0
           to the child process. If the fork is unsuccessful it "warn"s and returns "undef".

OTHER METHODS

       Proc::Daemon also defines some other functions. See source code for more details:

       OpenMax( [ $NUMBER ] )
           Returns the maximum file descriptor number. If undetermined $NUMBER will be returned.

       adjust_settings
           Does some fixes/adjustments on the "new" settings together with "fix_filename".

       fix_filename( $KEYNAME )
           Prevents double use of same filename in different processes.

       get_pid( [ $STRING ] )
           Returns the wanted PID if it can be found.

       get_pid_by_proc_table_attr( $ATTR, $MATCH )
           Returns the wanted PID by looking into the process table, or "undef". Requires the
           "Proc::ProcessTable" module to be installed.

NOTES

       "Proc::Daemon::init" is still available for backwards capability.

AUTHORS

       Primary-maintainer and code writer until version 0.03:

       ·   Earl Hood, earl@earlhood.com, http://www.earlhood.com/

       Co-maintainer and code writer since version 0.04:

       ·   Detlef Pilzecker, http://search.cpan.org/~deti/, http://www.secure-sip-server.net/

CREDITS

       Initial implementation of "Proc::Daemon" derived from the following sources:

       ·   "Advanced Programming in the UNIX Environment" by W. Richard Stevens.  Addison-Wesley,
           Copyright 1992.

       ·   "UNIX Network Programming", Vol 1, by W. Richard Stevens.  Prentice-Hall PTR,
           Copyright 1998.

PREREQUISITES

       This module requires the "POSIX" module to be installed.

       The "Proc::ProcessTable" module is not essentially required but it can be useful if it is
       installed (see above).

SEE ALSO

       perl(1), POSIX, Proc::ProcessTable

COPYRIGHT

       This module is Copyright (C) 1997-2011 by Earl Hood and Detlef Pilzecker.

       All Rights Reserved.

       This module is free software. It may be used, redistributed and/or modified under the same
       terms as Perl itself.