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+---
+name: shellcheck-configuration
+description: Master ShellCheck static analysis configuration and usage for shell script quality. Use when setting up linting infrastructure, fixing code issues, or ensuring script portability.
+---
+
+# ShellCheck Configuration and Static Analysis
+
+Comprehensive guidance for configuring and using ShellCheck to improve shell script quality, catch common pitfalls, and enforce best practices through static code analysis.
+
+## When to Use This Skill
+
+- Setting up linting for shell scripts in CI/CD pipelines
+- Analyzing existing shell scripts for issues
+- Understanding ShellCheck error codes and warnings
+- Configuring ShellCheck for specific project requirements
+- Integrating ShellCheck into development workflows
+- Suppressing false positives and configuring rule sets
+- Enforcing consistent code quality standards
+- Migrating scripts to meet quality gates
+
+## ShellCheck Fundamentals
+
+### What is ShellCheck?
+
+ShellCheck is a static analysis tool that analyzes shell scripts and detects problematic patterns. It supports:
+- Bash, sh, dash, ksh, and other POSIX shells
+- Over 100 different warnings and errors
+- Configuration for target shell and flags
+- Integration with editors and CI/CD systems
+
+### Installation
+
+```bash
+# macOS with Homebrew
+brew install shellcheck
+
+# Ubuntu/Debian
+apt-get install shellcheck
+
+# From source
+git clone https://github.com/koalaman/shellcheck.git
+cd shellcheck
+make build
+make install
+
+# Verify installation
+shellcheck --version
+```
+
+## Configuration Files
+
+### .shellcheckrc (Project Level)
+
+Create `.shellcheckrc` in your project root:
+
+```
+# Specify target shell
+shell=bash
+
+# Enable optional checks
+enable=avoid-nullary-conditions
+enable=require-variable-braces
+
+# Disable specific warnings
+disable=SC1091
+disable=SC2086
+```
+
+### Environment Variables
+
+```bash
+# Set default shell target
+export SHELLCHECK_SHELL=bash
+
+# Enable strict mode
+export SHELLCHECK_STRICT=true
+
+# Specify configuration file location
+export SHELLCHECK_CONFIG=~/.shellcheckrc
+```
+
+## Common ShellCheck Error Codes
+
+### SC1000-1099: Parser Errors
+```bash
+# SC1004: Backslash continuation not followed by newline
+echo hello\
+world  # Error - needs line continuation
+
+# SC1008: Invalid data for operator `=='
+if [[ $var =  "value" ]]; then  # Space before ==
+    true
+fi
+```
+
+### SC2000-2099: Shell Issues
+
+```bash
+# SC2009: Consider using pgrep or pidof instead of grep|grep
+ps aux | grep -v grep | grep myprocess  # Use pgrep instead
+
+# SC2012: Use `ls` only for viewing. Use `find` for reliable output
+for file in $(ls -la)  # Better: use find or globbing
+
+# SC2015: Avoid using && and || instead of if-then-else
+[[ -f "$file" ]] && echo "found" || echo "not found"  # Less clear
+
+# SC2016: Expressions don't expand in single quotes
+echo '$VAR'  # Literal $VAR, not variable expansion
+
+# SC2026: This word is non-standard. Set POSIXLY_CORRECT
+# when using with scripts for other shells
+```
+
+### SC2100-2199: Quoting Issues
+
+```bash
+# SC2086: Double quote to prevent globbing and word splitting
+for i in $list; do  # Should be: for i in $list or for i in "$list"
+    echo "$i"
+done
+
+# SC2115: Literal tilde in path not expanded. Use $HOME instead
+~/.bashrc  # In strings, use "$HOME/.bashrc"
+
+# SC2181: Check exit code directly with `if`, not indirectly in a list
+some_command
+if [ $? -eq 0 ]; then  # Better: if some_command; then
+
+# SC2206: Quote to prevent word splitting or set IFS
+array=( $items )  # Should use: array=( $items )
+```
+
+### SC3000-3999: POSIX Compliance Issues
+
+```bash
+# SC3010: In POSIX sh, use 'case' instead of 'cond && foo'
+[[ $var == "value" ]] && do_something  # Not POSIX
+
+# SC3043: In POSIX sh, use 'local' is undefined
+function my_func() {
+    local var=value  # Not POSIX in some shells
+}
+```
+
+## Practical Configuration Examples
+
+### Minimal Configuration (Strict POSIX)
+
+```bash
+#!/bin/bash
+# Configure for maximum portability
+
+shellcheck \
+  --shell=sh \
+  --external-sources \
+  --check-sourced \
+  script.sh
+```
+
+### Development Configuration (Bash with Relaxed Rules)
+
+```bash
+#!/bin/bash
+# Configure for Bash development
+
+shellcheck \
+  --shell=bash \
+  --exclude=SC1091,SC2119 \
+  --enable=all \
+  script.sh
+```
+
+### CI/CD Integration Configuration
+
+```bash
+#!/bin/bash
+set -Eeuo pipefail
+
+# Analyze all shell scripts and fail on issues
+find . -type f -name "*.sh" | while read -r script; do
+    echo "Checking: $script"
+    shellcheck \
+        --shell=bash \
+        --format=gcc \
+        --exclude=SC1091 \
+        "$script" || exit 1
+done
+```
+
+### .shellcheckrc for Project
+
+```
+# Shell dialect to analyze against
+shell=bash
+
+# Enable optional checks
+enable=avoid-nullary-conditions,require-variable-braces,check-unassigned-uppercase
+
+# Disable specific warnings
+# SC1091: Not following sourced files (many false positives)
+disable=SC1091
+
+# SC2119: Use function_name instead of function_name -- (arguments)
+disable=SC2119
+
+# External files to source for context
+external-sources=true
+```
+
+## Integration Patterns
+
+### Pre-commit Hook Configuration
+
+```bash
+#!/bin/bash
+# .git/hooks/pre-commit
+
+#!/bin/bash
+set -e
+
+# Find all shell scripts changed in this commit
+git diff --cached --name-only | grep '\.sh$' | while read -r script; do
+    echo "Linting: $script"
+
+    if ! shellcheck "$script"; then
+        echo "ShellCheck failed on $script"
+        exit 1
+    fi
+done
+```
+
+### GitHub Actions Workflow
+
+```yaml
+name: ShellCheck
+
+on: [push, pull_request]
+
+jobs:
+  shellcheck:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Run ShellCheck
+        run: |
+          sudo apt-get install shellcheck
+          find . -type f -name "*.sh" -exec shellcheck {} \;
+```
+
+### GitLab CI Pipeline
+
+```yaml
+shellcheck:
+  stage: lint
+  image: koalaman/shellcheck-alpine
+  script:
+    - find . -type f -name "*.sh" -exec shellcheck {} \;
+  allow_failure: false
+```
+
+## Handling ShellCheck Violations
+
+### Suppressing Specific Warnings
+
+```bash
+#!/bin/bash
+
+# Disable warning for entire line
+# shellcheck disable=SC2086
+for file in $(ls -la); do
+    echo "$file"
+done
+
+# Disable for entire script
+# shellcheck disable=SC1091,SC2119
+
+# Disable multiple warnings (format varies)
+command_that_fails() {
+    # shellcheck disable=SC2015
+    [ -f "$1" ] && echo "found" || echo "not found"
+}
+
+# Disable specific check for source directive
+# shellcheck source=./helper.sh
+source helper.sh
+```
+
+### Common Violations and Fixes
+
+#### SC2086: Double quote to prevent word splitting
+
+```bash
+# Problem
+for i in $list; do done
+
+# Solution
+for i in $list; do done  # If $list is already quoted, or
+for i in "${list[@]}"; do done  # If list is an array
+```
+
+#### SC2181: Check exit code directly
+
+```bash
+# Problem
+some_command
+if [ $? -eq 0 ]; then
+    echo "success"
+fi
+
+# Solution
+if some_command; then
+    echo "success"
+fi
+```
+
+#### SC2015: Use if-then instead of && ||
+
+```bash
+# Problem
+[ -f "$file" ] && echo "exists" || echo "not found"
+
+# Solution - clearer intent
+if [ -f "$file" ]; then
+    echo "exists"
+else
+    echo "not found"
+fi
+```
+
+#### SC2016: Expressions don't expand in single quotes
+
+```bash
+# Problem
+echo 'Variable value: $VAR'
+
+# Solution
+echo "Variable value: $VAR"
+```
+
+#### SC2009: Use pgrep instead of grep
+
+```bash
+# Problem
+ps aux | grep -v grep | grep myprocess
+
+# Solution
+pgrep -f myprocess
+```
+
+## Performance Optimization
+
+### Checking Multiple Files
+
+```bash
+#!/bin/bash
+
+# Sequential checking
+for script in *.sh; do
+    shellcheck "$script"
+done
+
+# Parallel checking (faster)
+find . -name "*.sh" -print0 | \
+    xargs -0 -P 4 -n 1 shellcheck
+```
+
+### Caching Results
+
+```bash
+#!/bin/bash
+
+CACHE_DIR=".shellcheck_cache"
+mkdir -p "$CACHE_DIR"
+
+check_script() {
+    local script="$1"
+    local hash
+    local cache_file
+
+    hash=$(sha256sum "$script" | cut -d' ' -f1)
+    cache_file="$CACHE_DIR/$hash"
+
+    if [[ ! -f "$cache_file" ]]; then
+        if shellcheck "$script" > "$cache_file" 2>&1; then
+            touch "$cache_file.ok"
+        else
+            return 1
+        fi
+    fi
+
+    [[ -f "$cache_file.ok" ]]
+}
+
+find . -name "*.sh" | while read -r script; do
+    check_script "$script" || exit 1
+done
+```
+
+## Output Formats
+
+### Default Format
+
+```bash
+shellcheck script.sh
+
+# Output:
+# script.sh:1:3: warning: foo is referenced but not assigned. [SC2154]
+```
+
+### GCC Format (for CI/CD)
+
+```bash
+shellcheck --format=gcc script.sh
+
+# Output:
+# script.sh:1:3: warning: foo is referenced but not assigned.
+```
+
+### JSON Format (for parsing)
+
+```bash
+shellcheck --format=json script.sh
+
+# Output:
+# [{"file": "script.sh", "line": 1, "column": 3, "level": "warning", "code": 2154, "message": "..."}]
+```
+
+### Quiet Format
+
+```bash
+shellcheck --format=quiet script.sh
+
+# Returns non-zero if issues found, no output otherwise
+```
+
+## Best Practices
+
+1. **Run ShellCheck in CI/CD** - Catch issues before merging
+2. **Configure for your target shell** - Don't analyze bash as sh
+3. **Document exclusions** - Explain why violations are suppressed
+4. **Address violations** - Don't just disable warnings
+5. **Enable strict mode** - Use `--enable=all` with careful exclusions
+6. **Update regularly** - Keep ShellCheck current for new checks
+7. **Use pre-commit hooks** - Catch issues locally before pushing
+8. **Integrate with editors** - Get real-time feedback during development
+
+## Resources
+
+- **ShellCheck GitHub**: https://github.com/koalaman/shellcheck
+- **ShellCheck Wiki**: https://www.shellcheck.net/wiki/
+- **Error Code Reference**: https://www.shellcheck.net/