Bash Scripting Habits That Prevent 3 a.m. Pages

Most shell scripts start as a quick fix and end up running in production for years. A few habits make the difference between a script that fails safely and one that quietly does the wrong thing.

1. Start every script in strict mode

#!/usr/bin/env bash
set -euo pipefail
IFS=$'\n\t'

• -e stops on the first failing command.
• -u treats unset variables as errors.
• -o pipefail makes a pipeline fail if any part of it fails.

2. Quote every variable

Unquoted variables split on spaces and expand wildcards. rm -rf $DIR/* with an empty $DIR is a very bad day. Write "$DIR" every time.

3. Log what you’re doing

log() { printf '%s [%s] %s\n' "$(date -Is)" "${0##*/}" "$*" >&2; }
log "Starting backup of $SOURCE"

4. Clean up with a trap

tmp=$(mktemp -d)
trap 'rm -rf "$tmp"' EXIT

5. Run ShellCheck

ShellCheck catches most quoting and logic mistakes before they reach a server. Add it to your CI pipeline and let it nag you.