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Re: process run in background

by stevieb (Canon)
on Jul 27, 2016 at 16:44 UTC ( #1168661=note: print w/replies, xml ) Need Help??

in reply to process run in background

I decided to write a much simpler, single-file example for you to examine using Proc::Background. I'll start with the starting, examining, input/output and stopping, then I'll show the code.

start the daemon

$ ./ start started daemon at PID 30216

verify it's running

$ ./ status is running at PID 30216 $ ps ax | grep 30216 30216 pts/4 S 0:00 perl perform

connect to the daemon

$ telnet localhost 6669 Trying Connected to localhost. Escape character is '^]'.

enter some input, and ensure the network daemon returns correctly

blah received: blah

network daemon closes connection

Connection closed by foreign host.

ensure the daemon is still running

$ ./ status is running at PID 30216 $ ps ax | grep 30216 30216 pts/4 S 0:00 perl perform

stop the daemon

$ ./ stop stopped PID 30216

ensure it's really stopped

$ ./ status is not running $ ps ax | grep 30216

Code. Note that although the usage printout doesn't show perform, if you run the script like ./script perform, it'll run in the foreground instead of going into the background. Note also I use $0 which holds the name of the script file, so no matter what you name the file, the output will always reflect the current script.

#!/usr/bin/perl use warnings; use strict; use IO::Socket::INET; use Proc::Background; if (! @ARGV || $ARGV[0] !~ /(?:start|stop|status|perform)/){ die "usage: $0 <start|stop|status>\n" } my $op = $ARGV[0]; my $pid_file = '/tmp/'; # this... start() if $op eq 'start'; stop() if $op eq 'stop'; status() if $op eq 'status'; perform() if $op eq 'perform'; # could also be written in a more concise way... #{ # no strict 'refs'; # &$op(); #} sub start { if (status(1)){ print "$0 already running at " ._get_pid(). "\n"; exit; } my $proc = Proc::Background->new("perl $0 perform"); my $pid = $proc->pid; print "started $0 daemon at PID $pid\n"; open my $wfh, '>', $pid_file or die $!; print $wfh $pid; close $wfh; } sub stop { my $pid; if (status(1)){ $pid = _get_pid(); kill 'KILL', $pid; unlink $pid_file; print "stopped $0 PID $pid\n"; } else { print "$0 doesn't appear to be running\n"; } } sub status { my $quiet = shift; my $pid = _get_pid(); my $status = $pid ? 1 : 0; if ($status){ print "$0 is running at PID $pid\n" if ! $quiet; } else { print "$0 is not running\n" if ! $quiet; } return $status; } sub perform { my $sock = new IO::Socket::INET ( LocalHost => '', LocalPort => 6669, Proto => 'tcp', Listen => 5, Reuse => 1, ); die "cannot create socket $!\n" unless $sock; while (1){ my $conn = $sock->accept; # below is what we receive from the client my $recv; $conn->recv($recv, 1024); # ...and this is what we send back my $send = "received: $recv\n"; $conn->send($send); shutdown($conn, 1); } $sock->close; } sub _get_pid { my $pid; if (-e $pid_file){ open my $fh, '<', $pid_file or die $!; $pid = <$fh>; close $fh; } return $pid; }

up-to-date version can be found on my github for future reference

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