Template for less error prone bash scripts

bash-script-template.md

Bash script template

#!/bin/bash

set -o errexit
set -o nounset
set -o pipefail
if [[ "${TRACE-0}" == "1" ]]; then set -o xtrace; fi
export SHELLOPTS

cd "$(dirname "$0")"

SCRIPT_DIR="$(pwd)"

Notes

• set -o errexit:
  • when a command fails, bash exits instead of continuing with the rest of the script
• set -o nounset:
  • the script will fail when accessing an unset variable
  • to access a variable that may or may not have been set, use "${VARNAME-}" instead of "$VARNAME"
• set -o pipefail:
  • a pipeline command is treated as failed, when one of the commands in the pipeline fail
• cd "$(dirname "$0")":
  • change to the script's directory
• if [[ "${TRACE-0}" == "1" ]]; then set -o xtrace; fi:
  • enables debug mode by running TRACE=1 ./script.sh
• remember to redirect error logs to stderr
  • i.e. echo 'Something unexpected happened' >&2
• export SHELLOPTS:
  • makes sub scripts inherit set options