How to run a command before a Bash script exits?

Question

If a Bash script has set -e, and a command in the script returns an error, how can I do some cleanup before the script exits?

For example:

#!/bin/bash
set -e
mkdir /tmp/foo
# ... do stuff ...
rm -r /tmp/foo

How can I ensure that /tmp/foo is removed, even if one of the commands in ... do stuff ... fails?

score 282 · Accepted Answer · edited Aug 14 '19 at 19:50

282

Here's an example of using trap:

#!/bin/bash -e

function cleanup {
  echo "Removing /tmp/foo"
  rm  -r /tmp/foo
}

trap cleanup EXIT
mkdir /tmp/foo
asdffdsa #Fails

Output:

dbrown@luxury:~ $ sh traptest
t: line 9: asdffdsa: command not found
Removing /tmp/foo
dbrown@luxury:~ $

Notice that even though the asdffdsa line failed, the cleanup still was executed.

edited Aug 14 '19 at 19:50

030

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answered Jan 25 '10 at 05:12

devguydavid

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To whom it may concern: This will also be executed when someone uses Ctrl+D or `exit` to end the current bash session. – Qqwy Aug 02 '22 at 18:37
Using `trap cleanup EXIT`, the *cleanup* function will **also** execute if the "command in the script does **not** return an error".... On the other hand, using e.g. `trap cleanup ERR` will execute the *cleanup* function only when there is an error, it will not execute if there is no error . Further information in https://stackoverflow.com/a/26261518/923560 – Abdull May 10 '23 at 11:52

score 16 · Answer 2 · edited May 23 '17 at 12:34

16

From the bash manpage (concerning builtins):

trap [-lp] [[arg] sigspec ...]
The command arg is to be read and executed when the shell receives signal(s) sigspec.

So, as indicated in Anon.'s answer, call trap early in the script to set up the handler you desire on ERR.

edited May 23 '17 at 12:34

Community

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answered Jan 25 '10 at 02:59

dmckee --- ex-moderator kitten

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Run `help trap` to see some help on the built-in. – Flimm Feb 27 '14 at 13:20

score 14 · Answer 3 · answered May 25 '19 at 07:21

14

sh version of devguydavid's answer.

#!/bin/sh
set -e
cleanup() {
  echo "Removing /tmp/foo"
  rm  -r /tmp/foo
}
trap cleanup EXIT
mkdir /tmp/foo
asdffdsa #Fails

ref: shellscript.sh

answered May 25 '19 at 07:21

Saftever

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`POSIX` makes me smile. :) Great teaching site you've linked to as well. – Cometsong May 31 '19 at 12:33

score 10 · Answer 4 · answered Jan 25 '10 at 02:45

10

From the reference for set:

-e

Exit immediately if a simple command (see section 3.2.1 Simple Commands) exits with a non-zero status, unless the command that fails is part of an until or while loop, part of an if statement, part of a && or || list, or if the command's return status is being inverted using !. A trap on ERR, if set, is executed before the shell exits.

(Emphasis mine).

answered Jan 25 '10 at 02:45

Anon.

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Might be worth adding "-E" when using "-e", see https://vaneyckt.io/posts/safer_bash_scripts_with_set_euxo_pipefail/ – Max Barraclough Feb 19 '20 at 21:20
FWIW the trap also runs on a regular script exit, i.e. in the happy path – nteissler Sep 18 '21 at 04:09

score 1 · Answer 5 · answered Oct 15 '21 at 06:21

I don't know if it matters to you if it's before or after.

You can set a script to run immediately after closing with "trap". and then you can close the terminal.

For Example;

    trap  ./val.sh EXIT  #set command you want to run after close terminal 
    kill -9 $PPID        #kill current terminal

How to run a command before a Bash script exits?

5 Answers5

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