Google Shell Style Detailed

Google Shell Style (Detailed)

Source: https://google.github.io/styleguide/shellguide.html

Pair with the quick reference: google-shell-style

This skill expands the short skill with section-level rules from Google's guide. For authoritative full text, see the official URL and reference.md.

How to use

1. Start from google-shell-style for everyday edits
2. Use this skill for reviews, ambiguous cases, or API/doc conventions
3. Consult reference.md for source paths and supplemental docs

Section rules

When to use Shell

• If you're mostly calling other utilities and are doing relatively little
• If performance matters, use something other than shell.
• If you are writing a script that is more than 100 lines long, or that uses
• When assessing the complexity of your code (e.g. to decide whether to switch

File Extensions

• If the executable will have a build rule that renames the source file
• If the executable will be added directly to the user's PATH, then prefer
• If neither of the above apply, then either choice is acceptable.

Function Comments

• Description of the function.
• Globals: List of global variables used and modified.
• Arguments: Arguments taken.
• Outputs: Output to STDOUT or STDERR.
• Returns: Returned values other than the default exit status of the last

Case statement

• Indent alternatives by 2 spaces.
• A one-line alternative needs a space after the close parenthesis of the
• Long or multi-command alternatives should be split over multiple lines with

Variable expansion

• Stay consistent with what you find for existing code.
• Quote variables, see Quoting section below.
• Don't brace-delimit single character shell specials / positional parameters,

Quoting

• Always quote strings containing variables, command substitutions, spaces or
• Use arrays for safe quoting of lists of elements, especially command-line
• Optionally quote shell-internal, readonly
• Prefer quoting strings that are "words" (as opposed to command options or
• Be aware of the quoting rules for pattern matches in [[ … ]]. See the
• Use "$@" unless you have a specific reason to use $*, such as simply

Arrays Pros

• Using Arrays allows lists of things without confusing quoting semantics.
• Arrays make it possible to safely store sequences/lists of arbitrary

Arithmetic

• particularly with set -e enabled. For example,