Expert bash/shell scripting across environments where Bash is available (Linux, macOS, Git Bash on Windows, WSL, containers). This is a Bash-focused skill - it does not provide PowerShell parity; on Windows the target is the Bash interpreter (Git Bash / WSL), not native PowerShell. PROACTIVELY activ

Bash Scripting Mastery Scope and platform contract This skill targets Bash itself , wherever Bash runs Linux, macOS, WSL, Git Bash / MSYS2 on Windows, and Bash based container images. It does not cover native PowerShell : a PowerShell script is a different language and should use powershell master . On Windows, bash master assumes the user is running Bash inside Git Bash, WSL, or a similar Bash environment, and addresses the MSYS path translation quirks that result. Repository conventions Project level conventions (Windows backslashes in tool calls, documentation discipline, etc.) live in the agent body and the windows path master plugin. This skill focuses on Bash content; do not duplicate that boilerplate here. Quick reference Bash portability quick check: When to use this skill Always activate for: Writing or modifying any bash/shell script Reviewing or refactoring existing scripts Debugging shell script failures DevOps automation, CI/CD pipelines, system administration Cross environment Bash portability (Linux < macOS < WSL < Git Bash < container) Do not use this skill for: PowerShell scripts use powershell master Batch ( .cmd / .bat ) scripting Generic command help unrelated to scripting Core principles 1. Safety first Every script should open with the safety preamble: 2. POSIX vs Bash Need to run on any UNIX sh !/bin/sh , no [[ ]] , no arrays, no process substitution Modern Linux/macOS with Bash !/usr/bin/env bash , prefer [[ ]] , arrays, regex Alpine/minimal containers Either install bash explicitly or write POSIX compliant sh 3. Quoting 4. ShellCheck Run shellcheck on every script. Only disable warnings with a justification comment: shellcheck disable=SC2086 reason: intentional word splitting . See references/best practices.md for the full quoting/style table and references/patterns antipatterns.md for the common pitfalls. Platform specific considerations Git Bash / MSYS2 (Windows) Git Bash auto converts Unix style arguments to Windows paths. This is the largest single source of cross platform Bash bugs on Windows. Full Git Bash + Windows path notes live in references/windows git bash paths.md . Linux GNU coreutils, /proc , systemd integration. Detect via [[ "$OSTYPE" == "linux gnu" ]] . macOS BSD utilities behave differently from GNU. Most common gotchas: sed i '' (empty string required), date flags differ, readlink f not available on stock macOS. WSL Effectively Linux. The Windows filesystem is mounted at /mnt/c/ . Detect via grep qi microsoft /proc/version . Containers Alpine images ship only /bin/sh (BusyBox). Write POSIX compliant scripts or apk add bash . Container init quirks: PID 1 must reap children and handle signals. Detect via [ f /.dockerenv ] or [ n "$KUBERNETES SERVICE HOST" ] . Portable platform detection template Full per platform tables (BSD vs GNU coreutils flags, WSL networking, container init patterns) live in references/platform specifics.md . Best practices (summary) The full patterns function design, error handling, input validation, argument parsing, logging live in references/in depth patterns.md . The headline rules: One concern per function; locals declared first; validate input; return non zero on error. Constants UPPER CASE ; locals lower case ; mark immutable values readonly . Always check exit codes ( if ! cmd , , traps, or a central error exit helper). Validate every external input empty, format, length, charset. Use getopts or a case based argument parser; print usage and exit 1 on bad input. Use a leveled logger that writes to stderr. Security, performance, testing, debugging, advanced patterns These each have dedicated sections in references/in depth patterns.md : Topic What it covers Security Command injection prevention, path traversal guards, privilege management, secure temp files Performance Avoiding subshells, bash built ins vs externals, process substitution, array ops Testing BATS unit tests, integration test patterns, CI/CD wiring Debugging set x , PS4 , conditional debug helpers, tracing and profiling Advanced patterns Safe config parsing, parallel processing, signal handling, retries with backoff Read that reference any time you need the canonical code template for one of those topics. Reference files [ references/platform specifics.md ](references/platform specifics.md) Detailed platform differences and workarounds [ references/best practices.md ](references/best practices.md) Comprehensive industry standards and guidelines [ references/patterns antipatterns.md ](references/patterns antipatterns.md) Common patterns and pitfalls with solutions [ references/windows git bash paths.md ](references/windows git bash paths.md) Git Bash / MSYS path translation reference [ references/in depth patterns.md ](references/in depth patterns.md) Function design, security, performance, testing, debugging, advanced patterns [ references/resources.md ](references/resources.md) Official docs, style guides, tooling, and learning links Success criteria A Bash script written with this skill should: 1. Pass shellcheck with no warnings 2. Begin with set euo pipefail 3. Quote every variable expansion 4. Print usage on h / help 5. Decompose into testable functions 6. Handle empty input, missing files, and unexpected arguments 7. Run on every target platform (Linux/macOS/WSL/Git Bash/container) where it claims support 8. Match the Google Shell Style Guide 9. Clean up on exit ( trap EXIT ) 10. Be unit tested with BATS where logic is non trivial Troubleshooting Script fails on a different platform checkbashisms script.sh to surface non portable constructs. command v tool to verify a required tool is installed. Diff command flags between GNU and BSD ( sed version etc.). ShellCheck warnings Read the rule explanation ( shellcheck W SC2086 ). Fix the underlying issue; only disable a rule with a justification comment. Works interactively but fails in cron Cron has a minimal PATH set PATH explicitly. Use absolute paths. Redirect stdout/stderr: ./script.sh /tmp/cron.log 2 &1 . Performance issues Profile with time . Enable set x to find slow steps. Replace external invocations with Bash built ins where possible.

bash-master