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Is it possible to customise the bash prompt to show the if there are any background jobs? I find it easy to forget that there are background jobs.

Say if the prompt was...

$

Is there a way to make it show the number of background jobs? For example, if there were two background jobs sent to the background using CTRL+Z, the prompt would be...

2 $
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1 Answer

up vote 10 down vote accepted

Put \j in your prompt. From the bash manual:

\j The number of jobs currently managed by the shell

Just remember that prompts do go stale and jobs can finish at any time, so if you have left the terminal idle, you'll want to redisplay the prompt.

At the cost of requiring an extra process just to print your prompt, you can make the \j only appear if any jobs exist.

PROMPT_COMMAND='hasjobs=$(jobs -p)'
PS1='${hasjobs:+\j }\$ '
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I want to make it so that it only shows this when there are background jobs, and have the usual prompt when there aren't any. What could I have it check for, so that I can use if and else (or is there a better way)? Thanks. – paradroid Apr 4 '12 at 21:11
@paradroid Sorry, I don't know of any non-ugly way to do that. Are you really sure that is necessary? – jw013 Apr 9 '12 at 23:54
Well, I'd like to do it, as long as it works fast enough. – paradroid Apr 10 '12 at 0:50
@paradroid I edited the answer to add a semi-ugly hack. As far as speed, the performance hit will be negligible on most modern systems. – jw013 Apr 10 '12 at 1:24
1  
Sorry, not a clairvoyant -- you'll have to be more specific about your unexpected results and what you did to get them. – jw013 Apr 10 '12 at 2:12
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