Bash Patterns Skill

Purpose: Optimize Bash tool usage in Claude Code workflows

Token efficiency: ~25 tokens metadata (always loaded), ~200-600 tokens on-demand (SKILL.md + resources)

Type: Type 6 Guidance-Only (no scripts, patterns only)

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Quick Reference

Temp Script Pattern

When to use: Complex logic (loops, conditionals), reusable operations, multi-step validation

Pattern:

1. Write complex logic to .cache/scripts/{name}.sh
2. Make executable: chmod +x .cache/scripts/{name}.sh
3. Execute: Bash(.cache/scripts/{name}.sh)
4. Result: Single approval (execute only, not each line)

Benefits:

• Single approval instead of 5-10 prompts
• Reusable across multiple runs
• Debuggable (inspect/modify script independently)
• Readable (multi-line clearer than one-liners)

See: resources/temp-scripts.md for complete pattern and examples

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Tool Selection Matrix

Operation	Prefer	Avoid	Why
Read file	Read tool	cat/head/tail	Dedicated tool, no approval
Search content	Grep tool	grep/rg via Bash	Regex support, context, no approval
Find files	Glob tool	find via Bash	Fast, pattern matching, no approval
Complex logic	Temp script	Bash one-liner	Single approval, readable

See: resources/approval-optimization.md for complete matrix and trade-offs

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Parallel Execution

Pattern: Multiple independent Bash calls in SINGLE message

Benefits:

• 2 operations: ~2x faster
• 4 operations: ~3-4x faster
• 8 operations: ~6-8x faster

Example:

# Sequential (slow)
Bash("git status && git diff && git log")

# Parallel (fast)
Bash("git status")
Bash("git diff")
Bash("git log")

See: resources/parallel-execution.md for batching guidelines and examples

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Capabilities

1. Temp Script Pattern

Eliminates approval prompts: Write complex Bash logic to .cache/scripts/ → single approval on execute

Use cases:

• Loops over files (for FILE in *.md; do ... done)
• Conditionals (if [[ -f file ]]; then ... fi)
• Multi-step validation (check → transform → verify)
• Reusable operations (run multiple times)

Anti-patterns:

• Complex one-liners forcing approval per line
• Inline loops in Bash tool calls
• Non-reusable validation logic

Details: resources/temp-scripts.md (~80-120 lines)

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2. Approval Optimization

Minimizes approval friction: Choose dedicated tools over Bash when possible

Tool selection principles:

• Read > cat/head/tail: Dedicated tool, line ranges, no approval
• Grep > grep/rg: Regex support, context lines, output modes, no approval
• Glob > find: Fast, pattern matching, mtime sorting, no approval
• Temp script > one-liner: Single approval for complex logic

Approval triggers:

• Pipes (|)
• Loops (for, while)
• Conditionals (if, case)
• Redirects (>, >>, 2>&1)

Trade-offs:

• Tool overhead (50ms) vs approval friction (5-10s per prompt)
• Sequential tool calls vs single Bash command
• Readability vs brevity

Details: resources/approval-optimization.md (~100-150 lines)

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3. Parallel Execution

Speeds up workflows: Multiple independent Bash calls in single message

Performance metrics (measured):

• 2 operations: ~2x speedup
• 4 operations: ~3-4x speedup
• 8 operations: ~6-8x speedup

Batching guidelines:

DO batch (independent operations):

• Status checks (git status, git diff, git log)
• File searches (find, ls, stat)
• Independent reads (cat file1, cat file2)

DON'T batch (dependencies):

• Read → Edit (must verify content first)
• Write → Read (verify write succeeded)
• Git add → commit (staging must precede commit)

Sequential dependencies: Use && chaining

Bash("mkdir dir && cd dir && touch file")

Details: resources/parallel-execution.md (~80-120 lines)

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4. Command Readability

Makes Bash commands maintainable: Patterns for quoting, heredocs, error handling

Patterns:

Git commit patterns:

# File-based commits (preferred when message in file)
git commit -F path/to/message.txt

# Inline commits (constructing on-the-fly)
git commit -m "$(cat <<'EOF'
Fix authentication bug

- Add token validation
- Handle expired tokens
- Update tests
EOF
)"

Comparison:

• -F: Cleaner (no subshell), safer escaping, direct file read
• Heredoc: Flexible (variable interpolation), inline construction

Quoting paths with spaces:

cd "/Users/name/My Documents"  # Correct
python "/path/with spaces/script.py"  # Correct

Error handling:

#!/bin/bash
set -e  # Exit on error
set -u  # Error on undefined variable
set -o pipefail  # Pipeline fails if any command fails

Debugging:

#!/bin/bash
set -x  # Print commands as executed
PS4='+ ${BASH_SOURCE}:${LINENO}: '  # Show file:line in trace

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Resources

Detailed Patterns

1. temp-scripts.md (~80-120 lines)

   • Complete temp script workflow
   • 3+ concrete before/after examples
   • Anti-patterns and gotchas
   • .cache/scripts/ structure

2. approval-optimization.md (~100-150 lines)

   • Complete tool selection matrix
   • Approval trigger identification
   • When Bash necessary vs when to avoid
   • 6+ concrete examples with trade-offs

3. parallel-execution.md (~80-120 lines)

   • Parallel vs sequential patterns
   • Batching guidelines (DO/DON'T)
   • Performance metrics
   • 4+ examples from codebase

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Integration

Complementary Skills

cli-dev: Documents what CLI tools do (fd, fzf, trash capabilities) bash-patterns: Documents how to use Bash tool in Claude Code framework: References bash-patterns for Bash optimization workflows

Quick Access

From project CLAUDE.md: Tool selection → delegates to this skill Auto-loading: Triggers on "Bash approval", "temp script", ".cache/scripts", "complex Bash"

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Progressive Disclosure Strategy

Metadata (25 tokens): Always loaded (frontmatter only) SKILL.md (400-500 lines): Loaded on skill invocation (this file) Resources (~50-150 lines each): Loaded on-demand (specific pattern needed)

Typical usage:

• 70% sessions: Metadata only (~25 tokens) - Bash mentioned, no deep dive
• 20% sessions: Metadata + 1 resource (~200 tokens) - Specific pattern needed
• 10% sessions: Metadata + multiple resources (~600 tokens) - Complex Bash work

Target savings: 86%+ vs loading all patterns upfront

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Success Metrics

Approval Reduction

• Before: Complex Bash → 5-10 approval prompts
• After: Temp script pattern → 1 approval (execute only)
• Savings: 80-90% approval reduction

Performance Improvement

• Before: Sequential Bash commands
• After: Parallel Bash calls in single message
• Speedup: 2-4x for common operations (status, diff, log)

Token Efficiency

• Baseline: ~500 tokens if all patterns loaded
• With progressive disclosure: ~25-200 tokens typical session
• Target: 86%+ savings

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When to Use

Use bash-patterns skill when:

• Encountering Bash approval prompts repeatedly
• Writing complex Bash commands (loops, conditionals)
• Working with .cache/scripts/ directory
• Choosing between Bash and dedicated tools (Read/Grep/Glob)
• Optimizing workflow performance (parallel execution)

Manual invocation:

"Show me the temp script pattern"
"How do I avoid Bash approval prompts?"
"What's the tool selection matrix for Bash vs Read/Grep/Glob?"
"How do I parallelize Bash operations?"