bash-patterns
Skill2 starsChanged 7 days agoMITView on GitHub
Bash and shell script patterns for safety flags, quoting, conditionals, traps, functions, ShellCheck discipline, and review-worthy anti-patterns. Use whenever the project contains `.sh`/`.bash`/`.zsh` files, files with a bash/sh shebang, scripts in `bin/`, shell dotfiles, or Makefile recipes, OR the user asks about shell scripting or a shell pipeline, even if "bash" is not mentioned by name.
In this repository37 other files it gives its agents.
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The file
We split this skill into the rules it gives an agent
1 rule. About 0 are common, 1 is distinctive, and 0 are very specific to this project.
≈0
Common · estimate
Many files like this have a rule of this kind.
≈1
Distinctive · estimate
This author's own choices. Worth a look.
0
Very specific
Tied to their project's names, files or tools. Probably skip.
- Common
- Distinctive
- Very specific
- Distinctive: line 8
Default assumption: bash 5.x targeting macOS (via Homebrew bash) and Linux.
≈ “Common” is an estimate: at least 1 in 5 of the 350,495 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.
Files
Bash patterns
- Default assumption: bash 5.x targeting macOS (via Homebrew bash) and Linux.
- Scripts use
#!/usr/bin/env bash, so the resolved binary is whatever is first on PATH -- on the user's machine that's the Homebrew 5.x build, not the stock macOS/bin/bash3.2. - Anything that requires bash 4.0+ (case modification,
mapfile) or 4.4+ (${parameter@op}) is unsafe under stock macOS bash; flagged here when the version cut matters.
Reference files
| File | Covers |
| reference/safety-flags.md | Script preamble, set -euo pipefail edge cases, inherit_errexit, nullglob, verification before shipping |
| reference/quoting.md | Quoting rules, nested quoting, heredoc indentation, printf over echo, zsh-vs-bash differences |
| reference/conditionals.md | [[ ]] over [ ], glob vs literal, numeric vs string comparison, (( )), case |
| reference/functions-and-traps.md | Functions and locals, trap patterns, BASH_LINENO / BASH_SOURCE / caller debug introspection |
| reference/parameter-expansion.md | ${var:-}, ${var:?}, prefix/suffix removal, pattern substitution, case modification |
| reference/subshells-and-pipes.md | Subshell semantics, | pitfalls, process substitution <(cmd), filesystem operations |
| reference/shellcheck.md | Top SC codes, suppression discipline, POSIX-only contexts (Alpine, BusyBox) |
| reference/anti-patterns.md | Fifteen review-time anti-patterns with severity calls |
References
- GNU Bash manual: https://www.gnu.org/software/bash/manual/bash.html
- POSIX shell command language: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
- ShellCheck wiki: https://www.shellcheck.net/wiki/
- BashFAQ: https://mywiki.wooledge.org/BashFAQ
- BashPitfalls: https://mywiki.wooledge.org/BashPitfalls
- BashGuide: https://mywiki.wooledge.org/BashGuide
- Google Shell Style Guide: https://google.github.io/styleguide/shellguide.html
Version notes
Checked: 2026-09-26 against https://ftp.gnu.org/gnu/bash/, https://tiswww.case.edu/php/chet/bash/NEWS, https://github.com/koalaman/shellcheck/releases
- 5.3 (2025-07-30; Homebrew 5.3.20): no guidance change; no 6.0 release exists. ShellCheck 0.11.0 (2025-08-04) current.
- 4.4:
shopt -s inherit_errexit,${parameter@op}(corrected from 4.0 per NEWS). 4.0: case modification,mapfile.
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