Bash: Getting PID of daemonized screen session

This show the pid for a screen named nameofscreen:

$ screen -ls
There are screens on:
    19898.otherscreen   (07/03/2012 05:50:45 PM)    (Detached)
    19841.nameofscreen  (07/03/2012 05:50:23 PM)    (Detached)
2 Sockets in /var/run/screen/S-sarnold.

$ screen -ls | awk '/\.nameofscreen\t/ {print strtonum($1)}'
19841
$ 

you can use:

screen -DmS nameofscreen

which does not fork a daemon process allowing you to know the pid.

Parsing the output of screen -ls can be unreliable if two screen sessions have been started with the same name. Another approach is to not let the screen session fork a process and put it in the background yourself:

For example with an existing initial screen session:

fess@hostname-1065% screen -ls
There is a screen on:
        19180.nameofscreen    (01/15/2013 10:11:02 AM)        (Detached)

create a screen using -D -m instead of -d -m which does not fork a new process. Put it in the background and get it's pid. (Using posix shell semantics)

fess@hostname-1066% screen -DmS nameofscreen & 
[3] 19431
fess@hostname-1067% pid=$! 

Now there are two screens both have the same name:

fess@hostname-1068% screen -ls
There are screens on:
        19431.nameofscreen    (01/15/2013 10:53:31 AM)        (Detached)
        19180.nameofscreen    (01/15/2013 10:11:02 AM)        (Detached)

but we know the difference:

fess@hostname-1069% echo $pid
19431

and we can accurately ask it to quit:

fess@hostname-1070% screen -S $pid.nameofscreen -X quit
[3]  - done       screen -DmS nameofscreen

now there's just the original one again:

fess@hostname-1071% screen -ls 
There is a screen on:
        19180.nameofscreen    (01/15/2013 10:11:02 AM)        (Detached)