Get PID of screen session started as daemon

marsupillami · 06-08-2009, 01:32 PM

Hello everyone,

I´m trying to start a screen session from a shell script. Here is how it looks like (simplified part):

Code:

cd /home/teste/14356/
screen -dmS 145363 ./execute.sh           
echo $$

It is returning me a wrong PID (example, it now returned 5205 when screen´s PID actually is 5207). How can I get the correct PID in order to store it and use it for further manipulation?

Thank You,

rweaver · 06-08-2009, 03:20 PM

Quote:

Originally Posted by marsupillami

Hello everyone,

I´m trying to start a screen session from a shell script. Here is how it looks like (simplified part):

Code:

cd /home/teste/14356/
screen -dmS 145363 ./execute.sh           
echo $$

It is returning me a wrong PID (example, it now returned 5205 when screen´s PID actually is 5207). How can I get the correct PID in order to store it and use it for further manipulation?

Thank You,

What's happening is its returning the PID of the bash shell.

Code:

cd /home/teste/14356/
screen -dmS asdfasdf ./execute.sh
screen -list | grep asdfasdf | cut -f1 -d'.' | sed 's/\W//g'

is kinda dirty but will work... might wanna make it more like:

Code:

#!/bin/bash
cd /home/teste/14356/
UNIQID=`date +%Y%M%d%H%M%S`
screen -dmS $UNIQID ./execute.sh
screen -list | grep $UNIQID | cut -f1 -d'.' | sed 's/\W//g'

You could further refine it by getting a directory and script to execute or taking the id from the commandline, etc.

marsupillami · 06-08-2009, 03:37 PM

Hello rweaver

That worked perfectly. Thank you very much!

rweaver · 06-08-2009, 03:57 PM

Quote:

Originally Posted by marsupillami

Hello rweaver

That worked perfectly. Thank you very much!

Also of note, you could just do a screen -list and it'll show all the running screens on the server for your user.

Also im not sure that screen command is going to do what you want... just a fyi.

Hko · 06-08-2009, 05:16 PM

You seem to know what you're doing, but just in case:

Why do you need the PID of the screen proces(ses)? If you're automating/scripting screen-stuff, you can probably do more with the session name you give the screen session(s) with the -S option than with it's PID.