Bash 3.2 compatibility

GitHub Action that fails when shell scripts use syntax the Bash shipped with macOS cannot run. That Bash is 3.2.

bash -n on Bash 3.2 still accepts some Bash 4 commands, because names such as mapfile look like ordinary commands. This action rejects those tokens, then parses every selected script with Bash 3.2.

Usage

- uses: actions/checkout@v4

- uses: hellosign/bash32-action@v1
  with:
    paths: |
      bin/**
      scripts/**/*.sh

paths is newline-separated globs relative to the repository root. A file is checked when its shebang contains bash. Other files matched by a glob, including sh and PHP scripts, are skipped. Each glob must match at least one Bash script.

The runner needs Docker. GitHub-hosted runners already have it.

Inputs

Name	Description	Default
paths	Newline-separated globs of files to consider.	Required
bash-image	Docker image that provides Bash 3.2.	bash:3.2

What it rejects

Bash 4 and newer syntax that bash -n does not catch on Bash 3.2:

• mapfile and readarray
• declare -A
• coproc
• [[ -v
• ${var^^}, ${var,,}, and ${var@Q}
• negative array indexes such as ${arr[-1]}
• &>> and |&

It also fails when Bash 3.2 itself cannot parse a script.

An empty array expanded under set -u ("${items[@]}" before any element is added) is a runtime error on Bash 3.2, not a parse error. This action does not execute the scripts, so it does not catch that case.