From: David Masover <ninja@...>
Date: 2009-12-15T10:21:25+09:00
Subject: Re: [OT] bash "wait for previous to finish" option?

On Monday 14 December 2009 04:57:49 pm Roger Pack wrote:
> two terminals open
> 
> 1) hack hack hack [start long running process]
> 2) hack hack [type in the name of a command which should be run
> immediately after long running process in terminal one finishes--and
> somehow it will start immediately afterward].

Definitely offtopic, but there a lot of answers, depending on what you 
actually want.

First, are you just talking about running one process after another? That's 
easy, semicolon, or && if you care about the return value. For example:

pv foo.tar | bzip2 -v9 > foo.tar.bz2 && rm foo.tar

Now, if you do care about them being in separate terminals, you need some way 
to signal the other terminal, and people mentioned various ways to do that. 
Probably the least hacky way might be something like:

mkfifo pipe
tar -cjpSf foo.tar.bz2 foo && echo > pipe

Then, in terminal two:

cat pipe && do_some_other_command

If your problem is that you already started the long-running process, and now 
you want to do something when it's done, that's done with wait. Easiest way, 
if the long-running job ignores terminal input, just type the name of the next 
command (and enter) and it'll probably go to bash. More thorough way, go to 
the terminal where you started it and suspend it with ctrl+Z. Then type 'bg' 
to allow it to continue in the background, and pay attention to the job 
number. Then you don't even need a pid, just wait %n, where n is the job 
number.

If you need to safely do this and then trigger something in that other window, 
you can probably figure out how to combine the above into something useful. 
Unfortunately, most of the time I think of things like this, I figure by the 
time I remember all my Unix tricks, the "long-running" job (of maybe a minute 
or two) will be done.