Bash background Jobs

20 June 2021

Sometimes it happen that inside the same terminal I need to do different things, so I need to stop some process and recalling some others.
Fortunately a Unix command come to the rescue: jobs.

Example of usage

Just to have a clean environment start a container

docker run -it ubuntu /bin/bash
# apt update && apt install -y vim

Show current top process

# top
top - 05:13:23 up 30 min,  0 users,  load average: 1.73, 1.95, 1.80
Tasks:   2 total,   1 running,   1 sleeping,   0 stopped,   0 zombie
%Cpu(s): 26.7 us,  6.2 sy,  0.0 ni, 65.8 id,  0.0 wa,  0.0 hi,  1.2 si,  0.0 st
MiB Mem :  2124.0 total,  2024.2 free,      100.0 used,   1539.4 buff/cache
MiB Swap:  164.0 total,    164.0 free,        0.0 used.    984.7 avail Mem

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
      1 root      20   0    4116   3468   2916 S   0.0   0.0   0:00.07 bash
     10 root      20   0    6108   3360   2824 R   0.0   0.0   0:00.01 top

Then press Ctrl + z to send it to background

[1]+  Stopped                 top

Check process stopped via jobs:

# jobs
[1]+  Stopped                 top

Start a new process in background using & at the end of the command:

# vi /tmp/baground.txt &
[2] 608
[2]+  Stopped                 vi /tmp/baground.txt

Using jobs could be find both:

# jobs
[1]-  Stopped                 top
[2]+  Stopped                 vi /tmp/baground.txt

Recall second task (vi /tmp/baground.txt) using %2, so if we want recall the first command we need to use %1:

# fg %2

Exit to vi using :q! (exit without saving)

# jobs
[1]-  Stopped                 top

The last command we use in this example is to close top sending a SIGTERM using kill command:

# kill %1

References