Bash scripts

A script is a text file with a shebang and shell commands. Scripts make repeatable what you would otherwise retype—deploy steps, backups, and local dev setup.

Minimal script structure

#!/usr/bin/env bash
set -euo pipefail
IFS=$'\n\t'
echo "Starting deploy..."
echo "Done."

set -euo pipefail is a common safety trio: exit on error, error on unset vars, fail pipelines on first error.

Running scripts

./deploy.sh          # needs execute bit
bash deploy.sh       # runs with bash even without +x

Prefer explicit bash script.sh in docs when execute bit might be missing.

Debugging

bash -x deploy.sh    # trace each command
set -x               # enable tracing inside script
set +x               # disable tracing

Tracing helps debug CI failures—compare with logs from Git CI lessons later.

Important interview questions and answers

1. Q: What does set -e do?
   A: Exit immediately if a command returns non-zero (with exceptions for some contexts).
2. Q: bash script.sh vs ./script.sh?
   A: The former needs no execute bit; the latter requires +x and honors shebang.

Self-check

1. Name three flags in the safety trio set -euo pipefail.
2. What flag prints commands as they run?

Tip: Start serious scripts with set -euo pipefail and a comment describing required tools.