Bash – Show error message if bash script terminates due to set -e

Under set -e, the non-existence of failfailfail causes the whole script to exit (or the subshell, if the function is executed in a subshell).

If you don't need to modify the shell state from the function, you can run it in a subshell.

myfunc() (
    set -e
    ls
    failfailfail
    uptime
)

Another approach in bash is to set an ERR trap to execute return. If you want to make it a local setting, you need to restore the old trap value, which is a little cumbersome.

myfunc() {
    local old_ERR_trap=$(trap -p ERR)
    if [[ -z $old_ERR_trap ]]; then old_ERR_trap="trap - ERR"; fi
    trap 'local ret=$?; eval "$old_ERR_trap"; return $ret' ERR
    ls
    failfailfail
    uptime
}

One option would be to put the commands in a bash script, and start it with set -e.

This will cause the script to terminate early if any command exits with non-zero exit status.

See also this question on stack overflow: https://stackoverflow.com/q/19622198/828193

To print the error, you could use

trap 'do_something' ERR

Where do_something is a command you would create to show the error.

Here is an example of a script to see how it works:

#!/bin/bash

set -e
trap 'echo "******* FAILED *******" 1>&2' ERR

echo 'Command that succeeds'   # this command works
ls non_existent_file           # this should fail
echo 'Unreachable command'     # and this is never called
                               # due to set -e

And this is the output:

$ ./test.sh 
Command that succeeds
ls: cannot access 'non_existent_file': No such file or directory
******* FAILED *******

Also, as mentioned by @jick, keep in mind that the exit status of a pipeline is by default the exit status of the final command in it. This means that if a non-final command in the pipeline fails, that won't be caught by set -e. To fix this problem if you are concerned with it, you can use set -o pipefail

As suggested my @glenn jackman and @Monty Harder, using a function as the handler can make the script more readable, since it avoids nested quoting. Since we are using a function anyway now, I removed set -e entirely, and used exit 1 in the handler, which could also make it more readable for some:

#!/bin/bash

error_handler() {
  echo "******* FAILED *******" 1>&2
  exit 1
}

trap error_handler ERR

echo 'Command that succeeds'   # this command works
ls non_existent_file           # this should fail
echo 'Unreachable command'     # and this is never called
                               # due to the exit in the handler

The output is identical as above, though the exit status of the script is different.