Shell Standards

Shell standards

The non-negotiable baseline for writing Bash that does not silently corrupt data or hide failures. Every rule is explained in depth, with citations, in [reference/shell-standards.md](../../reference/shell-standards.md); the rules that carry a ShellCheck code also have a runnable good/bad pair in [examples/standards/](../../examples/standards/).

Rules at a glance

| # | Rule | Why | Enforced by | |---|------|-----|-------------| | 1 | set -euo pipefail at the top | Fail fast; unset vars and broken pipes become errors | style guide | | 2 | Quote every expansion: "$var", "$(cmd)" | Prevents word-splitting and globbing | SC2086 | | 3 | read -r, never bare read | Bare read mangles backslashes | SC2162 | | 4 | Declare local, then assign | local x="$(cmd)" hides the command's exit status | SC2155 | | 5 | Arrays for lists; expand "${arr[@]}" | A string can't hold an element with spaces | SC2206 | | 6 | [[ ... ]], not [ ... ] | [[ ]] doesn't split or glob its operands | SC2292 | | 7 | return from helpers, exit only in main | exit kills the caller's shell when sourced | style guide | | 8 | trap '...' EXIT for cleanup | Releases temp files on every exit path | style guide | | 9 | printf, not echo | Portable escapes; keep data out of the format | SC2028/SC2059 | | 10 | Brace expansions: ${var} | Disambiguates ${v}_x, arrays, defaults | SC2250 | | 11 | readonly constants; command -v not which | Immutability; portable existence check | style guide | | 12 | Never parse ls; use a glob | Breaks on odd filenames | SC2045 |

How to use

• Writing a script? Start from rule 1, quote everything (rule 2), and reach

for arrays (rule 5) the moment you have a list of arguments.

• Reviewing a script? Run shellcheck at its default severity (this

repo's .shellcheckrc sets enable=all); the SC codes above map directly to these rules. CI lints at --severity=warning, which catches the higher-severity codes but filters out SC2086/SC2162 (info) and SC2292 (style) — so review locally at the default level to see them all.

• Formatting? shfmt (configured in .editorconfig) enforces layout — it

even rewrites legacy backticks to $(...) for you, which is why there is no runnable backticks example here.

See also: [skills/bash](../bash/), [skills/zsh](../zsh/), and [skills/nushell](../nushell/) for shell-specific guidance.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: posidoni
• Source: posidoni/shell-skill
• License: MIT

Install and usage instructions live in the source repository linked above.