sbusso · March 5, 2012 13:50 · Mar 5, 2012 · Nov 17, 2011 · Nov 17, 2011
diff --git a/simple_ruby_daemon.rb b/simple_ruby_daemon.rb
@@ -37,16 +37,18 @@
 class SimpleDaemon
   # Checks to see if the current process is the child process and if not
   # will update the pid file with the child pid.
-  def self.start(pid, pidfile)
+  def self.start pid, pidfile, outfile, errfile
     unless pid.nil?
       raise "Fork failed" if pid == -1
-      write(pid, pidfile) if kill(pid, pidfile)
+      write pid, pidfile if kill pid, pidfile
       exit
+    else
+      redirect outfile, errfile
     end
   end
 
   # Attempts to write the pid of the forked process to the pid file.
-  def self.write(pid, pidfile)
+  def self.write pid, pidfile
     File.open pidfile, "w" do |f|
       f.write pid
     end
@@ -74,18 +76,28 @@ def self.kill(pid, pidfile)
     $stderr.puts "While signaling the PID, unexpected #{e.class}: #{e}"
     false
   end
+
+  # Send stdout and stderr to log files for the child process
+  def self.redirect outfile, errfile
+    $stdin.reopen '/dev/null'
+    out = File.new outfile, "a"
+    err = File.new errfile, "a"
+    $stdout.reopen out
+    $stderr.reopen err
+    $stdout.sync = $stderr.sync = true
+  end
 end
 
 # Process name of your daemon
 $0 = "simple ruby daemon"
 
 # Spawn a deamon
-SimpleDaemon.start fork, (ARGV.first || '/tmp/simple_ruby_deamon.pid')
+SimpleDaemon.start fork, (ARGV[0] || '/tmp/deamon.pid'), (ARGV[1] || '/tmp/daemon.stdout.log'), (ARGV[2] || '/tmp/daemon.stderr.log')
 
 # Set up signals for our daemon, for now they just exit the process.
-Signal.trap("HUP") { puts "SIGHUP and exit"; exit }
-Signal.trap("INT") { puts "SIGINT and exit"; exit }
-Signal.trap("QUIT") { puts "SIGQUIT and exit"; exit }
+Signal.trap("HUP") { $stdout.puts "SIGHUP and exit"; exit }
+Signal.trap("INT") { $stdout.puts "SIGINT and exit"; exit }
+Signal.trap("QUIT") { $stdout.puts "SIGQUIT and exit"; exit }
 
 # Remove this loop and replace with your own daemon logic.
 loop do

diff --git a/simple_ruby_daemon.rb b/simple_ruby_daemon.rb
@@ -11,13 +11,13 @@
 # 1 second sleep.
 #
 # Most of the code is dedicated to managing a pid file. We want a pid
-# file so we can use a monitoring tool to make sure your daemon keeps
+# file so we can use a monitoring tool to make sure our daemon keeps
 # running.
 #
 # === Why?
 #
 # Writing a daemon sounds hard but as you can see is not that
-# complicated so lets strip away the magic and just write some ruby.
+# complicated, so lets strip away the magic and just write some ruby.
 #
 # === Usage
 #
@@ -29,7 +29,7 @@
 #
 #     $ ./simple_ruby_daemon.rb tmp/simple_ruby_daemon.pid
 #
-# You can check that it is running by running the following:
+# check that it is running by running the following:
 #
 #     $ ps aux | grep simple_ruby_daemon
 #
@@ -58,16 +58,17 @@ def self.write(pid, pidfile)
   # Try and read the existing pid from the pid file and signal the
   # process. Returns true for a non blocking status.
   def self.kill(pid, pidfile)
-    Process.kill "HUP", open(pidfile).read.strip.to_i
+    opid = open(pidfile).read.strip.to_i
+    Process.kill "HUP", opid
     true
   rescue Errno::ENOENT
     $stdout.puts "#{pidfile} did not exist: Errno::ENOENT"
     true
   rescue Errno::ESRCH
-    $stdout.puts "Process for the existing PID was not running: Errno::ESRCH"
+    $stdout.puts "The process #{opid} did not exist: Errno::ESRCH"
     true
   rescue Errno::EPERM
-    $stderr.puts "Lack of privileges to manage #{pidfile}: Errno::EPERM"
+    $stderr.puts "Lack of privileges to manage the process #{opid}: Errno::EPERM"
     false
   rescue ::Exception => e
     $stderr.puts "While signaling the PID, unexpected #{e.class}: #{e}"
@@ -89,4 +90,4 @@ def self.kill(pid, pidfile)
 # Remove this loop and replace with your own daemon logic.
 loop do
   sleep 1
-end
+end
diff --git a/simple_ruby_daemon.rb b/simple_ruby_daemon.rb
@@ -0,0 +1,92 @@
+#!/usr/bin/env ruby
+# == Simple Daemon
+#
+# A simple ruby daemon that you copy and change as needed.
+# 
+# === How does it work?
+#
+# All this program does is fork the current process (creates a copy of
+# itself) then exits, the fork (child process) then goes on to run your
+# daemon code. In this example we are just running a while loop with a
+# 1 second sleep.
+#
+# Most of the code is dedicated to managing a pid file. We want a pid
+# file so we can use a monitoring tool to make sure your daemon keeps
+# running.
+#
+# === Why?
+#
+# Writing a daemon sounds hard but as you can see is not that
+# complicated so lets strip away the magic and just write some ruby.
+#
+# === Usage
+#
+# You can run this daemon by running:
+#
+#     $ ./simple_ruby_daemon.rb
+#
+# or with an optional pid file location as its first argument:
+#
+#     $ ./simple_ruby_daemon.rb tmp/simple_ruby_daemon.pid
+#
+# You can check that it is running by running the following:
+#
+#     $ ps aux | grep simple_ruby_daemon
+#
+# Author:: Rufus Post  (mailto:rufuspost@gmail.com)
+class SimpleDaemon
+  # Checks to see if the current process is the child process and if not
+  # will update the pid file with the child pid.
+  def self.start(pid, pidfile)
+    unless pid.nil?
+      raise "Fork failed" if pid == -1
+      write(pid, pidfile) if kill(pid, pidfile)
+      exit
+    end
+  end
+
+  # Attempts to write the pid of the forked process to the pid file.
+  def self.write(pid, pidfile)
+    File.open pidfile, "w" do |f|
+      f.write pid
+    end
+  rescue ::Exception => e
+    $stderr.puts "While writing the PID to file, unexpected #{e.class}: #{e}"
+    Process.kill "HUP", pid
+  end
+
+  # Try and read the existing pid from the pid file and signal the
+  # process. Returns true for a non blocking status.
+  def self.kill(pid, pidfile)
+    Process.kill "HUP", open(pidfile).read.strip.to_i
+    true
+  rescue Errno::ENOENT
+    $stdout.puts "#{pidfile} did not exist: Errno::ENOENT"
+    true
+  rescue Errno::ESRCH
+    $stdout.puts "Process for the existing PID was not running: Errno::ESRCH"
+    true
+  rescue Errno::EPERM
+    $stderr.puts "Lack of privileges to manage #{pidfile}: Errno::EPERM"
+    false
+  rescue ::Exception => e
+    $stderr.puts "While signaling the PID, unexpected #{e.class}: #{e}"
+    false
+  end
+end
+
+# Process name of your daemon
+$0 = "simple ruby daemon"
+
+# Spawn a deamon
+SimpleDaemon.start fork, (ARGV.first || '/tmp/simple_ruby_deamon.pid')
+
+# Set up signals for our daemon, for now they just exit the process.
+Signal.trap("HUP") { puts "SIGHUP and exit"; exit }
+Signal.trap("INT") { puts "SIGINT and exit"; exit }
+Signal.trap("QUIT") { puts "SIGQUIT and exit"; exit }
+
+# Remove this loop and replace with your own daemon logic.
+loop do
+  sleep 1
+end