How to run a command after an already running, existing one finishes?

Question

If I start a script that is going to take a long time, I inevitably realize it after I've started the script, and wish I had a way of doing some kind of alert once it finishes.

So, for example, if I run:

really_long_script.sh

and press enter...how can I run another command once it finishes?

Answer 1

You can separate multple commands by ;, so they are executed sequentally, for example:

really_long_script.sh ; echo Finished

If you wish to execute next program only if the script finished with return-code 0 (which usually means it has executed correctly), then:

really_long_script.sh && echo OK

If you want the opposite (i.e. continue only if current command has failed), than:

really_long_script.sh || echo FAILED

You could run your script in a background (but beware, scripts output (stdout and stderr) would continue to go to your terminal unless you redirect it somewhere), and then wait for it:

really_long_script.sh &
dosomethingelse
wait; echo Finished

If you have alredy run script, you could suspend it with Ctrl-Z, and then execute something like:

fg ; echo Finished

Where fg brings the suspended process to foreground (bg would make it run in backgroung, pretty much like started whith &)

Answer 2

Turns out this isn't that hard: You can simply type the next command into the window while the existing one runs, press enter, and when the first one finishes, the second command will automatically run.

I'm guessing there are more elegant ways, but this does seem to work.

Editing to add that if you want to run an alert after the command finishes, you can create these aliases in .bashrc, then run alert while it is running:

 alias alert_helper='history|tail -n1|sed -e "s/^\s*[0-9]\+\s*//" -e "s/;\s*alert$//"'
 alias alert='notify-send -i gnome-terminal "Finished Terminal Job" "[$?] $(alert_helper)"'

Answer 3

I'm not sure if this is too simple to be what you wanted, but...

In all the Linux (well, all Unix) shells I've ever used, you can simply type the next command you want to run, and press return, whilst the first command is running.

Then, as soon as the first command finishes, the shell just processes your next command. And of course you can type multiple extra commands: they'll just get run in sequence.

Answer 4

You can also use bash's job control. If you started

$ really_long_script.sh

then press ctrl+z to suspend it:

^Z
[1]+  Stopped                 really_long_script.sh
$ bg

to restart the job in the background (just as if started it with really_long_script.sh &). Then you can wait for this background job with

$ wait N && echo "Successfully completed"

where N is the job ID (probably 1 if you didn't run any other background jobs) which is also displayed as [1] above.