Skilllibrary cross-platform-shell

install

source · Clone the upstream repo

git clone https://github.com/merceralex397-collab/skilllibrary

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/merceralex397-collab/skilllibrary "$T" && mkdir -p ~/.claude/skills && cp -r "$T/10-cli-systems-and-ops/cross-platform-shell" ~/.claude/skills/merceralex397-collab-skilllibrary-cross-platform-shell && rm -rf "$T"

manifest: 10-cli-systems-and-ops/cross-platform-shell/SKILL.md

source content

Purpose

Write shell scripts and Makefile recipes that execute correctly on Linux, macOS, and Windows (Git Bash / WSL / MSYS2).

When to use this skill

a shell script must run on both Linux and macOS (BSD vs GNU coreutils)
writing Makefile recipes or CI scripts targeting multiple OS runners
replacing
```
sed -i
```
,
```
grep -P
```
,
```
readlink -f
```
with portable alternatives
a project has contributors on macOS, Linux, and Windows

Do not use this skill when

the script only targets Linux — prefer
```
bash
```
the task is Windows PowerShell automation — different domain
building a compiled CLI tool — prefer
```
cli-development-go
```

Procedure

Use POSIX sh when possible — start with
```
#!/bin/sh
```
for max portability. Only use
```
#!/usr/bin/env bash
```
if arrays or
```
[[ ]]
```
are needed.
Avoid GNU extensions — use
```
sed 's/a/b/'
```
not
```
sed -i 's/a/b/'
```
(macOS
```
sed -i
```
requires
```
''
```
). Use
```
grep -E
```
not
```
grep -P
```
.
Use portable path resolution — replace
```
readlink -f
```
with
```
cd "$(dirname "$0")" && pwd -P
```
.
Handle line endings — ensure scripts use LF. Add
```
.gitattributes
```
:
```
*.sh text eol=lf
```
.

Abstract OS differences — detect OS with

uname -s

and branch:

case "$(uname -s)" in Darwin*) ... ;; Linux*) ... ;; MINGW*|MSYS*) ... ;; esac

Use
env
for interpreters —

#!/usr/bin/env python3

not

#!/usr/bin/python3

Test in CI on all targets — use GitHub Actions matrix with
```
ubuntu-latest
```
,
```
macos-latest
```
,
```
windows-latest
```
.

Portability cheat sheet

Task	GNU/Linux	macOS (BSD)	Portable
In-place edit	`sed -i 's/a/b/'`	`sed -i '' 's/a/b/'`	Write to temp, `mv`
Regex grep	`grep -P`	N/A	`grep -E`
Resolve symlink	`readlink -f`	N/A	`cd && pwd -P`
Create temp file	`mktemp`	`mktemp`	`mktemp -t prefix.XXXXXX`
Date format	`date -d`	`date -j -f`	Use `date +%s` for epoch

Decision rules

If you need
```
sed -i
```
, write to a temp file and
```
mv
```
it back — works everywhere.
Prefer
```
printf
```
over
```
echo -e
```
— echo behavior varies across shells.
Use
```
command -v
```
instead of
```
which
```
— POSIX compliant.
Avoid associative arrays — they require Bash 4+ (macOS ships Bash 3).
In Makefiles, set
```
SHELL := /bin/bash
```
only if Bash features are required.

References

Related skills

```
bash
```
— Linux-focused shell scripting
```
linux-ubuntu-ops
```
— Linux-specific operations
```
cli-development-go
```
— compiled cross-platform binary (avoids shell entirely)