Remember that in Bash each command in pipeline is executed in a subshell

This took me some time to debug recently so wanted to share. Not new or so at all, but good to be reminded that from time to time :-)

$ function aaa() {
>   return 10 | true
> }
$ aaa
$ echo $?
0

Above can surprise a bit (why the heck I'm not getting exit code 10 when that return was executed?) especially when hidden in some bigger chunk of code, but with set -o pipefail I get what I wanted:

$ set -o pipefail
$ aaa
$ echo $?
10