On 13.12.2009 00:51, Iñáki Baz Castillo wrote:
> El SáÃado, 12 de Diciembre de 2009, Robert Klemme escribi
>> This is what I would do:
>>
>> VAR='/var/run'
>>
>> pid_file = File.join(VAR, File.basename($0) + '.pid')
>>
>> begin
>>     old_pid = File.read(pid_file).to_i
>>     Process.kill 0, old_pid
>>     $stderr.puts "ERROR: already running with PID #{old_pid}"
>>     exit 1
>> rescue Errno::ENOENT
>>     # no pid file
>> rescue Errno::ESRCH
>>     # process not running
>>     $stderr.puts 'WARNING: stale pid file'
>> end
>>
>> # open file with EXCL in order to catch race conditions where two
>> # processes were started almost at the same time and both thought
>> # they would be a new instance.  Uncomment sleep to simulate:
>> # sleep 2
>> File.open(pid_file, File::EXCL | File::WRONLY | File::CREAT) {|io|
>> io.write($$)}
>> trap(0) {File.delete pid_file}
>>
>> puts "OK, here we go."
>
>
> Let me a question: is the above a fragment of a Linux init script written in
> Ruby (rather than bash/sh as usual)?

That was hacked together for demonstration purposes.  It was not 
intended as an init script but rather as the demon itself - albeit 
without all the demonization stuff (detaching from terminal etc.) 
because I wanted to focus on the aspect of pid file handling and killing.> If so, according to LSB specifications it should return 0 (success) in case of
> "start" action when the daemon is already running.

Well, if you write a start script for that "ruby demon" you would have 
to handle exit codes properly.

Kind regards

	robert


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