launching process and keeping track of pid

[Joe Van Dyk]

Hi,

How can I launch a program from Ruby and monitor it to see if it's
running? On a unix platform.

I assume I'd probably need to launch the program, capture the pid of
the started process somehow, and start a thread that monitors the
/proc directory to see if the pid is in there?

Thanks,
Joe

 

[Ara.T.Howard]

Hi,

How can I launch a program from Ruby and monitor it to see if it's
running? On a unix platform.

I assume I'd probably need to launch the program, capture the pid of
the started process somehow, and start a thread that monitors the
/proc directory to see if the pid is in there?

Thanks,
Joe

this might be helpful:

#
# returns true if pid is running, false otherwise
#
def alive pid
#--{{{
pid = Integer("#{ pid }")
begin
Process::kill 0, pid
true
rescue Errno::ESRCH
false
end
#--}}}
end
alias alive? alive

cheers.


-a
--
===============================================================================
| email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| My religion is very simple. My religion is kindness.
| --Tenzin Gyatso
===============================================================================

 

[Joe Van Dyk]

On Sat, 25 Jun 2005, Joe Van Dyk wrote:
=20
=20
this might be helpful:
=20
#
# returns true if pid is running, false otherwise
#
def alive pid
#--{{{
pid =3D Integer("#{ pid }")
begin
Process::kill 0, pid
true
rescue Errno::ESRCH
false
end
#--}}}
end
alias alive? alive
=20

Thanks!=20

I asked a question similar to this a couple months ago and you
responded with the following code. However, my Ruby-fu isn't strong
enough to decipher it (the optfilter and IO bit). Any chance you
could add some comments to it?


class BackGroundProcess
attr :argv
attr pts
attr id
def initialize(*args)
@argv, @opts =3D optfilter args
return if((@pid =3D fork))
perform_redirects
exec(*@argv)
end
def perform_redirects
if((io =3D (opts[:stdout] or opts['stdout'])))
STDOUT.reopen(IO =3D=3D=3D io ? io : open(io,'w'))
end
if((io =3D (opts[:stderr] or opts['stderr'])))
STDERR.reopen(IO =3D=3D=3D io ? io : open(io,'w'))
end
end
def optfilter list
hashes, args =3D list.partition{|elem| Hash =3D=3D=3D elem}
opts =3D hashes.inject(accum=3D{}){|accum, h| accum.update h}
[ args, opts ]
end
end

 

[Ara.T.Howard]

this might be helpful:

#
# returns true if pid is running, false otherwise
#
def alive pid
#--{{{
pid = Integer("#{ pid }")
begin
Process::kill 0, pid
true
rescue Errno::ESRCH
false
end
#--}}}
end
alias alive? alive

Thanks!

I asked a question similar to this a couple months ago and you
responded with the following code. However, my Ruby-fu isn't strong
enough to decipher it (the optfilter and IO bit). Any chance you
could add some comments to it?


class BackGroundProcess
attr :argv
attr pts
attr id
def initialize(*args)
@argv, @opts = optfilter args
return if((@pid = fork))
perform_redirects
exec(*@argv)
end
def perform_redirects
if((io = (opts[:stdout] or opts['stdout'])))
STDOUT.reopen(IO === io ? io : open(io,'w'))
end
if((io = (opts[:stderr] or opts['stderr'])))
STDERR.reopen(IO === io ? io : open(io,'w'))
end
end
def optfilter list
hashes, args = list.partition{|elem| Hash === elem}
opts = hashes.inject(accum={}){|accum, h| accum.update h}
[ args, opts ]
end
end

optfilter just takes things that looks like options and uses them as options,
things that are not hashes are arugments. it just let's you do things like

options = {'stdout' => StringIO::new}

BackGroundProcess::new 'cat', options, 'stderr' => StringIO::new

or

BackGroundProcess::new options, 'cat', 'stderr' => StringIO::new

basically it just yanks out all the hashes as options with later hashes
over-riding earlier ones... not important at all ;-)

-a
--
===============================================================================
| email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| My religion is very simple. My religion is kindness.
| --Tenzin Gyatso
===============================================================================