Running script in background?

bobbyright · 03-01-2010, 12:14 PM

If I wanted to run a script in the background and keep it running even if i close putty i do like

./perl.pl &

right?

tom4everitt · 03-01-2010, 12:21 PM

That will run it in the background in the sense that you will get a new prompt.

If you want it to "survive" the terminal that you started it in (or putty in your case) you should start it with

nohup ./perl.pl &

or have a look at the screen command.

Prehistorik · 03-01-2010, 12:30 PM

Not quite. The script process will still be a child of your remotely open shell, so it will be terminated when you disconnect. A better solution is to use screen:

Code:

screen -S u ./perl.pl

-S tells screen to create a session from scratch
u is the name of your screen session in which the script is being run. You may choose a different one if you like
After all the options and the session name your command goes (along with arguments, if any).

Then you detach it (Ctrl-A, then Ctrl-D) and log out of the SSH session. To reattach it and see the results of your script you may log in to your remote server again and issue a command:

Code:

screen -d -r u

-r tells screen to reattach the detached session
-d is used to detach it first if it is already attached elsewhere
Again, u is your session name

Prehistorik · 03-01-2010, 12:33 PM

Quote:

Originally Posted by tom4everitt

nohup ./perl.pl &

Didn't know that before, thanks a lot

tom4everitt · 03-02-2010, 02:17 AM

No problem

Prehistoriks way (with the screen command) is more powerful and perhaps also more common. Its very convenient, especially when you're connected from a remote location. It sort of allows you to have several terminals (screens) in the same terminal.

The nohup (which comes from "no hangup", so you remember it

) is sort of neat in its simpleness though.