bashconventions

name: BashConventions version: 0.1.0 description: "Bash and shell scripting pitfalls — BSD vs GNU tools, set -euo pipefail traps, glob behavior, subprocess env. USE WHEN writing or reviewing shell scripts (.sh files), Makefiles with shell recipes, or install scripts." paths: - "/*.sh" - "/Makefile"

Tooling

macOS ships BSD tools — shasum -a 256 not sha256sum, BSD awk lacks 3-arg match().

set -euo pipefail traps

grep with 0 matches → exit 1. Fix: grep ... || true
((VAR++)) with VAR=0 → exit 1. Fix: VAR=$((VAR + 1))
[ cond ] && action where cond is false → exit 1. Fix: if [ cond ]; then action; fi
find | while read runs loop in subshell. Fix: while read; done < <(find ...)

printf flags collision

printf '---\n...' fails — printf parses --- as flags. Use heredoc or printf '%s\n' '---'.

Glob and dotfiles

cp -r dir/* skips dotfiles — the * glob doesn't match hidden files. Use cp -r dir/. (trailing /.) when destination must include hidden files. Common silent bug: install scripts that drop .manifest, .env, .provenance/ etc. without error.

Python subprocess proxy inheritance

Python subprocesses inherit proxy env vars even after unset in the parent bash shell. When calling Python scripts that make HTTP requests from bash, use env -u http_proxy -u https_proxy python3 script.py, or add urllib.request.install_opener(urllib.request.build_opener(urllib.request.ProxyHandler({}))) at the top of the Python script.

Additional references

@BashPatterns.md