bash tricks

#◊site/notes

Assigning default values to shell variables with a single command in bash - Stack Overflow

FOO="${VARIABLE:-default}"  # If variable not set or null, use default.
# If VARIABLE was unset or null, it still is after this (no assignment done).

FOO="${VARIABLE:=default}"  # If variable not set or null, set it to default.

Catch your errors:

#!/bin/bash
set -eu -o pipefail

• set -e — halt on errors (non-zero exit from subprocesses)
• set -u — halt on unset variables
• set -o pipefail — halt if a pipeline component fails