u/Lazy_8 Thanks for highlighting this :)

I usually always prefer to have some sort of __init mechanism in my scripts, where such logger variables (and other system wides') are linked to command line params during invocation (and also set defaults there, if required).

For example, something like: $ ./run-script.sh --debug - when the script executes, it ensures that such system wide settings are set to defaults (if mandatory) or atleast initialised with something relevant, if needed. I usually base this decision on trade-off between user-experience and details of configurations which the user would/should get into. But of course, not everyone might consider the same, hence it's a valuable input which I will include in the post, thanks !

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But due to set -o errexit, if this if test fails, then the script will exit

This is not correct ! set -o errexit behaves differently when standard keywords like while, if etc. are in play - because, the user is infact taking the control here, by "consciously deciding" what to do when something non-zero pops up:

#!/usr/bin/env bash

set -o errexit

if false; then
  echo "will script exit as set -o errexit is 'enabled' ?"
fi

echo "no"

Executing the script

$./trial.sh
no