How to send jobs to background without stopping them?

you can run "bg" to run it in the background.

"fg" moves it to the foreground

Note that bg and fg take job #s instead of PIDs, so if you've got multiple jobs running at once, use the "jobs" command to get the job numbers.

you can also start a program as a background job with an "&" on the command line.

e.g.

myprogram &

note that output (both stdout and stderr) will still go to the current tty, so it's generally a good idea to redirect to /dev/null or to a log file, like so:

myprogram > ~/program.log 2>&1 &

in either example, it's a background job like any other, so you can still bring it back to the foreground with 'fg' (but if you've redirected output you won't see much).

In bash, entering a "bg" puts the job into the background until it blocks needing input. It will continue to output to STDERR and STDOUT which might be unhelpful. You can enter "fg" to bring the job back to the foreground.

[adjuster@mx02 ~]$ cp ~/crap/* ~/crap2 
(Ctrl-Z)
[1]+  Stopped                cp ~/crap ~/crap2 

[adjuster@mx02 ~]$ cp ~/crap3/* ~/crap4
(Ctrl-Z)
[2]+  Stopped                cp ~/crap3/* ~/crap

[adjuster@mx02 ~]$ jobs
[1]+  Stopped                cp ~/crap ~/crap2 
[2]+  Stopped                cp ~/crap3/* ~/crap

[adjuster@mx02 ~]$ bg 1
[1]- cp ~/crap ~/crap2 &
[1]-  Exit 1                  cp ~/crap ~/crap2 

[adjuster@mx02 ~]$ fg 2
[adjuster@mx02 ~]$ 

So, that was starting a long copy job and suspending it, starting a second long copy job and suspending it, then putting the first copy job into the background and letting it run, followed by that first copy job exiting. Then I put the last copy job into the foreground and let it finish.

nohup task.sh &

Runs in background, output goes to nohup.out in current directory. Continues to run when you log out.

Another option is the excellent screen utility, which can be used to run many processes at the same time, without having to keep a terminal open. It also allows for much easier interactivity than bg and fg.