Michael Twomey's Blog

shell

osh is a great drop in bash replacement

Apr 23, 2025

Nine Reasons to Use OSH oils.pub

I’ve starting using osh for testing my bash scripts (mostly used in build and deployments). It’s been great for both giving better error messages and spotting problems shellcheck mightn’t catch.

This has been my favourite so far:

osh -o strict:all ./myscript.sh
    if assert_task_definition_is_older "${task_definition}" "deployed"; then
    ^~
myscript.sh:119: errexit was disabled for this construct

    if assert_task_definition_is_older "${task_definition}" "deployed"; then
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
myscript.sh:119: fatal: Can't run a proc while errexit is disabled. Use 'try' or wrap it in a process with $0 myproc

This leads to this interesting note on how errexit and if statements invoking shell functions lead to surprising behaviour (basically errexit is disabled).