Update to Unix Copilot

{
  "description": "Translate commands and scripts between Bash, zsh, POSIX sh, GNU/Linux and stock BSD/macOS tools.",
  "included_files": [],
  "name": "portability-macos-linux",
  "skill_md_contents": "---\nname: portability-macos-linux\ndescription: Translate commands and scripts between Bash, zsh, POSIX sh, GNU/Linux and stock BSD/macOS tools.\n---\n\n# macOS, Linux and shell portability\n\n## Scope and execution truth\nThis is a skills-only assistant workflow. Do not claim to execute system commands, inspect the user's host, install packages, or complete side effects without actual authorized tools and observed results. User-pasted output is evidence, not a machine connection.\n\n## Procedure\n1. Identify operating system, shell, utility implementation and version before assuming compatibility.\n2. Inspect OS-dependent commands (`sed -i`, `date`, `stat`, `find`, `xargs`, `readlink`, `sort`, `grep`) and shell constructs (arrays, `[[ ]]`, `pipefail`).\n3. Prefer the portable POSIX interface when reasonable. For nonportable behavior, provide clearly labeled alternatives rather than an inaccurate universal snippet.\n4. Check `zsh` interactive versus scripting differences, and note stock macOS defaults without assuming actual interpreter.\n5. Avoid unnecessary system-wide GNU tool installation; choose a portable alternative or explain the dependency.\n6. Include a quick compatibility test or shell syntax check if relevant.\n\n## Relevant references\n- Read `../../references/portability-matrix.md` for domain-specific guidance.\n- Read `../../references/source-registry.md` for domain-specific guidance.\n- Read `../../references/shell-quoting.md` for domain-specific guidance.\n\n## Completion checks\n- GNU/BSD differences explicit\n- Selected shebang supports constructs\n- Platform claims sourced when version-sensitive\n\n## Deliverable\nUse the minimum format that makes the answer actionable: the actual command or patch, platform assumptions, a preview before risky changes, and a reproducible validation step. Clearly label proposed actions versus observed execution.\n"
}