Bash header for safer code

header.bash

#!/bin/bash

set -e # exit on error
set -u # error on undefined variable
set -o posix # errors in $() expressions propagate outwards
set -o pipefail # errors in a pipeline will propagate outwards

# set -e
# Any command returning a nonzero code will exit the script
# If you need to run a command that may file, use it either in `if` expressions, or part of an `or` expression such as `command || true`

# set -u
# Using undefined variables such as $THING will fail thanks
# If you still need to use env variables, e.g. to know if they were passed in, use ${THING:-}, which means $THING if it's provided, and the empty string if it isn't

# set -o posix
# Normally, if you do something like `var=$(false)`, this will not propagate the error
# in POSIX mode, the error propagates
# note that this changes a bunch of other behaviors, mostly minor changes

# set -o pipefail
# Normally, if part of a pipeline fail but the last command succeeds, the pipeline counts as a success
# `syntaxerror | true` will not result in script failure
# pipefail fixes that so it will fail the script rather than just plodding along quietly