your shell lets you run many programs (“jobs”) in the same terminal tab

programs can either be:

• foreground
• background
• stopped (which is more like “paused”)

& runs a program in the background

for example I like to convert 100 files in parallel like this:

for i in `seq 1 100`
do
   convert $i.png $i.jpg &
done

jobs lists backgrounded & stopped jobs

$ jobs
[1] Running python blah.py &
[2] Stopped vim

use the numbers to bring them to the foreground or background (like fg %2), kill them (kill %2), or disown them

when you close a terminal tab all jobs are killed with a SIGHUP signal

you can stop this with disown or by starting the program with nohup: disown %1 (job number goes here) nohup my_program &

a trick to kill programs if Ctrl+C doesn’t work

1. press Ctrl+Z to stop the program
2. run kill %1 to kill it (or kill -9 %1 if you’re feeling extra murderous)

a little flowchart

Three boxes, labelled “running in foreground”, “stopped”, and “running in background”

Ctrl+Z goes from “running in foreground” to “stopped” fg goes from “stopped” to “running in foreground” fg goes from “running in background” to “running in foreground” bg goes from “stopped” to “running in background”