Job Control

Pause, run in background, run in foreground

Let’s create a process which is rather long to complete :

$ sleep 1000

To pause the process, type Ctrl + Z :

^Z
[1]+  Stopped                 sleep 1000

You can use jobs to see the list of processes running or stopped in the current terminal :

$ jobs
[1]+  Stopped                 sleep 1000

To bring back a job on the foreground, use fg with the id written between brackets in the list provided by jobs :

$ fg 1                                                     
sleep 1000

When a job is stopped, you can run it in background with the command bg with the same id :

$ bg 1                                                     
[1]+ sleep 1000 &

And then see it in the list of jobs in the current terminal :

$ jobs                                                     
[1]+  Running                 sleep 1000 &

To directly run a job in background, finish the command with & :

$ jobs                                                     
[1]+  Running                 sleep 1000 &                                      
$ sleep 5000 &
[2] 6743                                                                        
$ jobs                                                     
[1]-  Running                 sleep 1000 &                                      
[2]+  Running                 sleep 5000 &

List, wait and stop processes

To get a list of the processes running in the current terminal, you can use ps :

$ sleep 1000 &
$ ps -opid,comm
  PID COMMAND
 1000 sh
 1001 sleep
 1002 ps

To kill a running process, use kill with the process ID (PID) indicated by ps:

$ kill 1001
$ ps -opid,comm
 PID COMMAND
1000 sh
1004 ps

To wait for a process to terminate, use the wait command :

$ sleep 10 && echo End &
$ ps -opid,comm
 PID COMMAND
1000 sh
1005 sh
1006 sleep
1007 ps
$ wait 1005 && echo Stop waiting
End
Stop waiting

First, we run a process with PID 1005 in background which will print “End” before ending. Then, we wait for this process to finish, and print “Stop waiting”. The output shows “End”, meaning the process with PID 1005 is complete, then “Stop waiting”, showing the wait command is complete.