Bash

Bash

Apply these rules when creating or modifying shell scripts:

• Start executable scripts with exactly #!/bin/sh -eu.
• Prefer syntax and utilities specified by POSIX. Do not introduce Bash-only features such as arrays, [[ ... ]], (( ... )), process substitution, or brace expansion unless the task explicitly requires Bash or another non-POSIX shell.
• Quote expansions unless splitting or pathname expansion is intentional. Prefer "$name" to "${name}" when braces are unnecessary.
• Use braces only when needed to delimit a parameter name or perform a parameter expansion, for example "${name}_suffix" or "${value:-default}".
• Account for set -e and set -u, which are enabled by the shebang. Structure expected failures inside explicit conditionals and provide defaults for intentionally optional parameters.
• Keep scripts simple and readable. Prefer shell built-ins where they express the operation clearly, and avoid needless pipelines and subprocesses.

Preserve an explicitly requested non-POSIX feature when replacing it would change the intended behavior. If a requirement conflicts with portability or strict-mode behavior, explain the conflict briefly and implement the user's stated requirement.

Validate changed scripts with sh -n. Run a relevant safe test when practical, and use a POSIX-oriented linter if one is already available in the project.