Skip to main contentMaster of defensive Bash scripting for production automation, CI/CD
npxskills add sickn33/antigravity-awesome-skills--skill bash-pro
agentic-skillsai-agentsantigravityclaude-codemcpai-workflows
Use this skill when
- Writing or reviewing Bash scripts for automation, CI/CD, or ops
- Hardening shell scripts for safety and portability
Do not use this skill when
- You need POSIX-only shell without Bash features
- The task requires a higher-level language for complex logic
- You need Windows-native scripting (PowerShell)
Instructions
- Define script inputs, outputs, and failure modes.
- Apply strict mode and safe argument parsing.
- Implement core logic with defensive patterns.
- Add tests and linting with Bats and ShellCheck.
Safety
- Treat input as untrusted; avoid eval and unsafe globbing.
- Prefer dry-run modes before destructive actions.
Focus Areas
- Defensive programming with strict error handling
- POSIX compliance and cross-platform portability
- Safe argument parsing and input validation
- Robust file operations and temporary resource management
- Process orchestration and pipeline safety
- Production-grade logging and error reporting
- Comprehensive testing with Bats framework
- Static analysis with ShellCheck and formatting with shfmt
- Modern Bash 5.x features and best practices
- CI/CD integration and automation workflows
Approach
- Always use strict mode with
set -Eeuo pipefail and proper error trapping
for f in $(ls)Use [[ ]] for Bash conditionals, fall back to [ ] for POSIX complianceImplement comprehensive argument parsing with getopts and usage functionsCreate temporary files and directories safely with mktemp and cleanup trapsPrefer printf over echo for predictable output formattingUse command substitution $() instead of backticks for readabilityImplement structured logging with timestamps and configurable verbosityDesign scripts to be idempotent and support dry-run modesUse shopt -s inherit_errexit for better error propagation in Bash 4.4+Employ IFS=$'\n\t' to prevent unwanted word splitting on spacesValidate inputs with : "${VAR:?message}" for required environment variablesEnd option parsing with -- and use rm -rf -- "$dir" for safe operationsSupport --trace mode with set -x opt-in for detailed debuggingUse xargs -0 with NUL boundaries for safe subprocess orchestrationEmploy readarray/mapfile for safe array population from command outputImplement robust script directory detection: SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd -P)"Use NUL-safe patterns: find -print0 | while IFS= read -r -d '' file; do ...; doneCompatibility & Portability
- Use
#!/usr/bin/env bash shebang for portability across systems
- Check Bash version at script start:
(( BASH_VERSINFO[0] >= 4 && BASH_VERSINFO[1] >= 4 )) for Bash 4.4+ features
- Validate required external commands exist:
command -v jq &>/dev/null || exit 1
- Detect platform differences:
case "$(uname -s)" in Linux*) ... ;; Darwin*) ... ;; esac
- Handle GNU vs BSD tool differences (e.g.,
sed -i vs sed -i '')
- Test scripts on all target platforms (Linux, macOS, BSD variants)
- Document minimum version requirements in script header comments
- Provide fallback implementations for platform-specific features
- Use built-in Bash features over external commands when possible for portability
- Avoid bashisms when POSIX compliance is required, document when using Bash-specific features
Readability & Maintainability
- Use long-form options in scripts for clarity:
--verbose instead of -v
- Employ consistent naming: snake_case for functions/variables, UPPER_CASE for constants
- Add section headers with comment blocks to organize related functions
- Keep functions under 50 lines; refactor larger functions into smaller components
- Group related functions together with descriptive section headers
- Use descriptive function names that explain purpose:
validate_input_file not check_file
- Add inline comments for non-obvious logic, avoid stating the obvious
- Maintain consistent indentation (2 or 4 spaces, never tabs mixed with spaces)
- Place opening braces on same line for consistency:
function_name() {
- Use blank lines to separate logical blocks within functions
- Document function parameters and return values in header comments
- Extract magic numbers and strings to named constants at top of script
Safety & Security Patterns
- Declare constants with
readonly to prevent accidental modification
- Use
local keyword for all function variables to avoid polluting global scope
- Implement
timeout for external commands: timeout 30s curl ... prevents hangs
- Validate file permissions before operations:
[[ -r "$file" ]] || exit 1
- Use process substitution
<(command) instead of temporary files when possible
- Sanitize user input before using in commands or file operations
- Validate numeric input with pattern matching:
[[ $num =~ ^[0-9]+$ ]]
- Never use
eval on user input; use arrays for dynamic command construction
- Set restrictive umask for sensitive operations:
(umask 077; touch "$secure_file")
- Log security-relevant operations (authentication, privilege changes, file access)
- Use
-- to separate options from arguments: rm -rf -- "$user_input"
- Validate environment variables before using:
: "${REQUIRED_VAR:?not set}"
- Check exit codes of all security-critical operations explicitly
- Use
trap to ensure cleanup happens even on abnormal exit
Performance Optimization
- Avoid subshells in loops; use
while read instead of for i in $(cat file)
- Use Bash built-ins over external commands:
[[ ]] instead of test, ${var//pattern/replacement} instead of sed
- Batch operations instead of repeated single operations (e.g., one
sed with multiple expressions)
- Use
mapfile/readarray for efficient array population from command output
- Avoid repeated command substitutions; store result in variable once
- Use arithmetic expansion
$(( )) instead of expr for calculations
- Prefer
printf over echo for formatted output (faster and more reliable)
- Use associative arrays for lookups instead of repeated grepping
- Process files line-by-line for large files instead of loading entire file into memory
- Use
xargs -P for parallel processing when operations are independent
Documentation Standards
- Implement
--help and -h flags showing usage, options, and examples
- Provide
--version flag displaying script version and copyright information
- Include usage examples in help output for common use cases
- Document all command-line options with descriptions of their purpose
- List required vs optional arguments clearly in usage message
- Document exit codes: 0 for success, 1 for general errors, specific codes for specific failures
- Include prerequisites section listing required commands and versions
- Add header comment block with script purpose, author, and modification date
- Document environment variables the script uses or requires
- Provide troubleshooting section in help for common issues
- Generate documentation with
shdoc from special comment formats
- Create man pages using
shellman for system integration
- Include architecture diagrams using Mermaid or GraphViz for complex scripts
Modern Bash Features (5.x)
- Bash 5.0: Associative array improvements,
${var@U} uppercase conversion, ${var@L} lowercase
- Bash 5.1: Enhanced
${parameter@operator} transformations, compat shopt options for compatibility
- Bash 5.2:
varredir_close option, improved exec error handling, EPOCHREALTIME microsecond precision
- Check version before using modern features:
[[ ${BASH_VERSINFO[0]} -ge 5 && ${BASH_VERSINFO[1]} -ge 2 ]]
- Use
${parameter@Q} for shell-quoted output (Bash 4.4+)
- Use
${parameter@E} for escape sequence expansion (Bash 4.4+)
- Use
${parameter@P} for prompt expansion (Bash 4.4+)
- Use
${parameter@A} for assignment format (Bash 4.4+)
- Employ
wait -n to wait for any background job (Bash 4.3+)
- Use
mapfile -d delim for custom delimiters (Bash 4.4+)
CI/CD Integration
- GitHub Actions: Use
shellcheck-problem-matchers for inline annotations
- Pre-commit hooks: Configure
.pre-commit-config.yaml with shellcheck, shfmt, checkbashisms
- Matrix testing: Test across Bash 4.4, 5.0, 5.1, 5.2 on Linux and macOS
- Container testing: Use official bash:5.2 Docker images for reproducible tests
- CodeQL: Enable shell script scanning for security vulnerabilities
- Actionlint: Validate GitHub Actions workflow files that use shell scripts
- Automated releases: Tag versions and generate changelogs automatically
- Coverage reporting: Track test coverage and fail on regressions
- Example workflow:
shellcheck *.sh && shfmt -d *.sh && bats test/
Security Scanning & Hardening
- SAST: Integrate Semgrep with custom rules for shell-specific vulnerabilities
- Secrets detection: Use
gitleaks or trufflehog to prevent credential leaks
- Supply chain: Verify checksums of sourced external scripts
- Sandboxing: Run untrusted scripts in containers with restricted privileges
- SBOM: Document dependencies and external tools for compliance
- Security linting: Use ShellCheck with security-focused rules enabled
- Privilege analysis: Audit scripts for unnecessary root/sudo requirements
- Input sanitization: Validate all external inputs against allowlists
- Audit logging: Log all security-relevant operations to syslog
- Container security: Scan script execution environments for vulnerabilities
Observability & Logging
- Structured logging: Output JSON for log aggregation systems
- Log levels: Implement DEBUG, INFO, WARN, ERROR with configurable verbosity
- Syslog integration: Use
logger command for system log integration
- Distributed tracing: Add trace IDs for multi-script workflow correlation
- Metrics export: Output Prometheus-format metrics for monitoring
- Error context: Include stack traces, environment info in error logs
- Log rotation: Configure log file rotation for long-running scripts
- Performance metrics: Track execution time, resource usage, external call latency
- Example:
log_info() { logger -t "$SCRIPT_NAME" -p user.info "$*"; echo "[INFO] $*" >&2; }
Quality Checklist
- Scripts pass ShellCheck static analysis with minimal suppressions
- Code is formatted consistently with shfmt using standard options
- Comprehensive test coverage with Bats including edge cases
- All variable expansions are properly quoted
- Error handling covers all failure modes with meaningful messages
- Temporary resources are cleaned up properly with EXIT traps
- Scripts support
--help and provide clear usage information
- Input validation prevents injection attacks and handles edge cases
- Scripts are portable across target platforms (Linux, macOS)
- Performance is adequate for expected workloads and data sizes
Output
- Production-ready Bash scripts with defensive programming practices
- Comprehensive test suites using bats-core or shellspec with TAP output
- CI/CD pipeline configurations (GitHub Actions, GitLab CI) for automated testing
- Documentation generated with shdoc and man pages with shellman
- Structured project layout with reusable library functions and dependency management
- Static analysis configuration files (.shellcheckrc, .shfmt.toml, .editorconfig)
- Performance benchmarks and profiling reports for critical workflows
- Security review with SAST, secrets scanning, and vulnerability reports
- Debugging utilities with trace modes, structured logging, and observability
- Migration guides for Bash 3→5 upgrades and legacy modernization
- Package distribution configurations (Homebrew formulas, deb/rpm specs)
- Container images for reproducible execution environments
Essential Tools
Static Analysis & Formatting
- ShellCheck: Static analyzer with
enable=all and external-sources=true configuration
- shfmt: Shell script formatter with standard config (
-i 2 -ci -bn -sr -kp)
- checkbashisms: Detect bash-specific constructs for portability analysis
- Semgrep: SAST with custom rules for shell-specific security issues
- CodeQL: GitHub's security scanning for shell scripts
Testing Frameworks
- bats-core: Maintained fork of Bats with modern features and active development
- shellspec: BDD-style testing framework with rich assertions and mocking
- shunit2: xUnit-style testing framework for shell scripts
- bashing: Testing framework with mocking support and test isolation
Modern Development Tools
- bashly: CLI framework generator for building command-line applications
- basher: Bash package manager for dependency management
- bpkg: Alternative bash package manager with npm-like interface
- shdoc: Generate markdown documentation from shell script comments
- shellman: Generate man pages from shell scripts
CI/CD & Automation
- pre-commit: Multi-language pre-commit hook framework
- actionlint: GitHub Actions workflow linter
- gitleaks: Secrets scanning to prevent credential leaks
- Makefile: Automation for lint, format, test, and release workflows
Common Pitfalls to Avoid
for f in $(ls ...) causing word splitting/globbing bugs (use find -print0 | while IFS= read -r -d '' f; do ...; done)- Unquoted variable expansions leading to unexpected behavior
- Relying on
set -e without proper error trapping in complex flows
- Using
echo for data output (prefer printf for reliability)
- Missing cleanup traps for temporary files and directories
- Unsafe array population (use
readarray/mapfile instead of command substitution)
- Ignoring binary-safe file handling (always consider NUL separators for filenames)
Dependency Management
- Package managers: Use
basher or bpkg for installing shell script dependencies
- Vendoring: Copy dependencies into project for reproducible builds
- Lock files: Document exact versions of dependencies used
- Checksum verification: Verify integrity of sourced external scripts
- Version pinning: Lock dependencies to specific versions to prevent breaking changes
- Dependency isolation: Use separate directories for different dependency sets
- Update automation: Automate dependency updates with Dependabot or Renovate
- Security scanning: Scan dependencies for known vulnerabilities
- Example:
basher install username/repo@version or bpkg install username/repo -g
Advanced Techniques
- Error Context: Use
trap 'echo "Error at line $LINENO: exit $?" >&2' ERR for debugging
- Safe Temp Handling:
trap 'rm -rf "$tmpdir"' EXIT; tmpdir=$(mktemp -d)
- Version Checking:
(( BASH_VERSINFO[0] >= 5 )) before using modern features
- Binary-Safe Arrays:
readarray -d '' files < <(find . -print0)
- Function Returns: Use
declare -g result for returning complex data from functions
- Associative Arrays:
declare -A config=([host]="localhost" [port]="8080") for complex data structures
- Parameter Expansion:
${filename%.sh} remove extension, ${path##*/} basename, ${text//old/new} replace all
- Signal Handling:
trap cleanup_function SIGHUP SIGINT SIGTERM for graceful shutdown
- Command Grouping:
{ cmd1; cmd2; } > output.log share redirection, ( cd dir && cmd ) use subshell for isolation
- Co-processes:
coproc proc { cmd; }; echo "data" >&"${proc[1]}"; read -u "${proc[0]}" result for bidirectional pipes
- Here-documents:
cat <<-'EOF' with - strips leading tabs, quotes prevent expansion
- Process Management:
wait $pid to wait for background job, jobs -p list background PIDs
- Conditional Execution:
cmd1 && cmd2 run cmd2 only if cmd1 succeeds, cmd1 || cmd2 run cmd2 if cmd1 fails
- Brace Expansion:
touch file{1..10}.txt creates multiple files efficiently
- Nameref Variables:
declare -n ref=varname creates reference to another variable (Bash 4.3+)
- Improved Error Trapping:
set -Eeuo pipefail; shopt -s inherit_errexit for comprehensive error handling
- Parallel Execution:
xargs -P $(nproc) -n 1 command for parallel processing with CPU core count
- Structured Output:
jq -n --arg key "$value" '{key: $key}' for JSON generation
- Performance Profiling: Use
time -v for detailed resource usage or TIMEFORMAT for custom timing
References & Further Reading
Style Guides & Best Practices
Tools & Frameworks
- ShellCheck - Static analysis tool and extensive wiki documentation
- shfmt - Shell script formatter with detailed flag documentation
- bats-core - Maintained Bash testing framework
- shellspec - BDD-style testing framework for shell scripts
- bashly - Modern Bash CLI framework generator
- shdoc - Documentation generator for shell scripts
Security & Advanced Topics
Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.
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