From: Amos <amos+lists.ruby-talk@...>
Date: 2001-05-02T22:23:03+09:00
Subject: [ruby-talk:14541] Re: daemon ruby script

>>>>> On Thu, 26 Apr 2001 19:10:09 +0900,
>>>>> Patrik Sundberg <ps@radiac.mine.nu> (ps) writes:

ps> I would like to have one of my ruby programs running in the background at all
ps> times like a normal UNIX daemon (it is a daemon logging temperature data to a
ps> database). I thought this would be a easy enough task since all the syscalls
ps> is right there from the start. I somehow don't manage to get it right anyway..
ps> I tried do write something along the lines of the BSD call daemon(3):

ps> --------------------------------------------------------------------------
ps> def daemon(doClose, doChdir)

ps>         if fork != nil
ps>                 exit(0);
ps>         end

ps>         Process.setsid

ps>         if doChdir 
ps>                 Dir.chdir("/")
ps>         end

ps>         if doClose
ps>                 $stdin.close
ps>                 $stdout.close
ps>                 $stderr.close
ps>                 $stdin = $stdout = $stderr = open("/dev/null", "rw")
ps>         end

ps> end

ps> [ read some args etc ]

ps> if fgFlag
ps>         main
ps> else
ps>         print "Fork to background! \n"
ps>         daemon(true, true)
ps>         main
ps> end
ps> --------------------------------------------------------------------------

I've also been working on a daemon process, one I'm hoping to put on
RAA before long.  Here's what I did, and it seems to be working
pretty well:


##
## Become a daemon!
##
def go_daemon
  unless Process.uid == 0
    $stderr.puts "#{$0} must be run as root!"
    exit!
  end
   
  Dir.chdir PrayConfig.wrkdr
  File.umask 077
  trap "SIGCLD", "IGNORE"

  if $DEBUG
    $stderr.puts "DEBUG enabled, running in foreground"
  else
    ## close unneeded descriptors
    $stdin.close
    $stdout.close
    $stderr.close

    ## drop into the background.
    pid = fork
    if pid
      ## parent: save pid of child, then exit
      File.open(PrayConfig.pidfl, "w") do |file|
        file.puts pid
      end
      exit!
    end

    ## change process group and lose control tty
    Process.setpgrp
  end

  ## Run at higher priority so that runaways won't get away, but try
  ## not to directly compete with sched, pageout, and fsflush.
  Process.setpriority Process::PRIO_PROCESS, Process.pid, -10

  ## Initialize syslog
  $thishost = Socket.gethostbyname(Socket.gethostname)[0]
  $sl = Syslog.new 'pray', Syslog::LOG_PID|Syslog::LOG_CONS, Syslog::LOG_DAEMON
end

##
## "MAIN"
##
go_daemon



-- 
Amos