Using CLIs Effectively

Skill Overview

This skill teaches you how to effectively discover, use, and integrate with command-line interfaces (CLIs), with particular focus on custom Python CLIs and tool wrappers.

Discovery Process

1. Start with Help

Always begin with --help:

# Basic help
<cli> --help

# Subcommand help
<cli> <subcommand> --help

# Some CLIs use -h
<cli> -h

Example:

python3 snippets_cli.py --help
python3 snippets_cli.py update --help

2. Explore the Source

For Python CLIs, read the argparse setup:

# Find the CLI file
find ~/.claude -name "*cli.py" | grep snippets

# Read the main function and argparse setup
grep -A 50 "argparse" <cli_file>
grep -A 20 "add_argument" <cli_file>

Look for:

• Subcommands (create, update, delete, list)
• Required vs optional arguments
• Flag types (store_true, choices, etc.)
• Default values

3. List Current State

Before modifying anything, understand what exists:

# List all items
<cli> list

# Get specific item details
<cli> get <name>

# Show current configuration
<cli> config show

Safe Usage Patterns

1. Dry Run First

Test commands without making changes:

# Many CLIs support dry-run
<cli> update <item> --dry-run
<cli> delete <item> --dry-run --verbose

2. Use Verbose Mode

See what's happening:

<cli> update <item> --verbose
<cli> update <item> -v
<cli> update <item> --debug

3. Create Backups

Before destructive operations:

# Check for backup flags
<cli> delete <item> --backup
<cli> update <item> --backup-dir ~/backups

# Or manually backup
cp config.json config.json.backup

4. Validate Before Execute

Use get/show commands to verify:

# 1. Check current state
<cli> get <name>

# 2. Plan your changes
<cli> update <name> --pattern "new-pattern" --dry-run

# 3. Execute
<cli> update <name> --pattern "new-pattern"

# 4. Verify
<cli> get <name>

Common CLI Patterns

CRUD Operations

Most CLIs follow CRUD patterns:

# Create
<cli> create <name> --pattern "..." --file content.md

# Read/List
<cli> list
<cli> get <name>

# Update
<cli> update <name> --pattern "new-pattern"
<cli> update <name> --file new-content.md

# Delete
<cli> delete <name>
<cli> delete <name> --force  # Skip confirmation

Configuration Management

Multiple config files:

# Default (usually local config)
<cli> update <name> --pattern "..."

# Specific config
<cli> update <name> --pattern "..." --config work

# Base config
<cli> update <name> --pattern "..." --base

Output Formats

Get machine-readable output:

# JSON output
<cli> list --json
<cli> get <name> --json

# Pipe to jq for filtering
<cli> list --json | jq '.[] | select(.enabled == true)'

# TSV for spreadsheets
<cli> list --format tsv

Integration Patterns

1. Scripting CLIs

Write scripts that use CLIs:

#!/bin/bash
set -e  # Exit on error

# Function to safely update snippet
update_snippet() {
    local name="$1"
    local pattern="$2"

    # Check if exists
    if ! snippets_cli.py get "$name" >/dev/null 2>&1; then
        echo "Error: Snippet '$name' not found"
        return 1
    fi

    # Update with backup
    snippets_cli.py update "$name" \
        --pattern "$pattern" \
        --backup

    echo "Updated $name"
}

# Use the function
update_snippet "download-pdf" "\\bDOWNLOAD\\b[.:;,]?"

2. Error Handling

Check exit codes:

if <cli> update <name> --pattern "..."; then
    echo "Success"
else
    echo "Failed with exit code $?"
    exit 1
fi

3. Parsing Output

Extract information from CLI output:

# Get JSON and parse
pattern=$(<cli> get <name> --json | jq -r '.pattern')

# Or use grep
<cli> get <name> | grep "pattern:" | cut -d'"' -f2

Real Example: Snippets CLI

Discovery

# 1. Find the CLI
find ~/.claude -name "snippets_cli.py"

# 2. Get help
python3 snippets_cli.py --help
python3 snippets_cli.py update --help

# 3. List current snippets
python3 snippets_cli.py list | head -20

Safe Update Workflow

cd ~/.claude/plugins/marketplaces/warren-claude-code-plugin-marketplace/claude-context-orchestrator/scripts

# 1. Check current state
python3 snippets_cli.py get download-pdf

# Output shows:
# "pattern": "\\b(DOWNLOAD|PDF)\\b[.:;,]?"

# 2. Update pattern only
python3 snippets_cli.py update download-pdf \
    --pattern "\\bDOWNLOAD\\b[.:;,]?"

# 3. Verify change
python3 snippets_cli.py get download-pdf | grep pattern

# 4. Check it works
python3 snippets_cli.py list | grep -A 5 "download-pdf"

Update Pattern and Content

# Update both at once
python3 snippets_cli.py update download-pdf \
    --pattern "\\bDOWNLOAD\\b[.:;,]?" \
    --file ~/new-content.md

# Or update from another snippet
python3 snippets_cli.py get other-snippet --json | \
    jq -r '.content' | \
    python3 snippets_cli.py update download-pdf --content -

Advanced Patterns

Batch Operations

Update multiple items:

# Using a loop
for snippet in mail gcal post; do
    python3 snippets_cli.py update "$snippet" --enabled true
done

# Or with xargs
echo "mail gcal post" | xargs -n1 python3 snippets_cli.py get

Programmatic Usage

Use CLIs from Python:

import subprocess
import json

def get_snippet(name):
    """Get snippet details via CLI"""
    result = subprocess.run(
        ['python3', 'snippets_cli.py', 'get', name, '--json'],
        capture_output=True,
        text=True
    )
    if result.returncode == 0:
        return json.loads(result.stdout)
    return None

def update_pattern(name, pattern):
    """Update snippet pattern via CLI"""
    result = subprocess.run(
        ['python3', 'snippets_cli.py', 'update', name,
         '--pattern', pattern],
        capture_output=True,
        text=True
    )
    return result.returncode == 0

Testing CLI Changes

Before committing changes:

# 1. Backup current config
cp config.local.json config.local.json.backup

# 2. Make changes
python3 snippets_cli.py update <name> --pattern "..."

# 3. Test in Claude
# (Send a message that should trigger the snippet)

# 4. If broken, restore
cp config.local.json.backup config.local.json

# 5. If working, commit
git add config.local.json
git commit -m "Update: Changed <name> pattern"

Troubleshooting

CLI Not Found

# Find it
find ~/.claude -name "*cli.py"
find ~/Desktop -name "*cli.py"

# Check PATH
which <cli-command>

# Use full path
python3 /full/path/to/cli.py

Permission Denied

# Make executable
chmod +x <cli-file>

# Or use python3 directly
python3 <cli-file>

Invalid Arguments

# Check help for exact syntax
<cli> <subcommand> --help

# Check if argument name is correct
# (sometimes --dry-run vs --dryrun)

# Read the source to be sure
grep "add_argument.*dry" <cli-file>

Config File Issues

# Validate JSON
cat config.local.json | python3 -m json.tool

# Check file exists
ls -la config*.json

# Check permissions
ls -la config.local.json

Best Practices Summary

1. Always check --help first
2. Read the source for Python CLIs (argparse section)
3. List before modifying (understand current state)
4. Use dry-run when available
5. Enable verbose mode for debugging
6. Create backups before destructive operations
7. Validate after changes (get/show commands)
8. Check exit codes in scripts
9. Use JSON output for programmatic use
10. Document your CLI usage (scripts, examples)

Related Skills

• MANAGESKILL - Managing and creating Agent Skills
• TDD - Test-driven development for CLI tools
• DEEPSEARCH - Finding CLIs and their documentation

Quick Reference Card

# Discovery
<cli> --help
<cli> <cmd> --help
grep -r "argparse" <cli-dir>

# Safe Operations
<cli> get <name>              # Check before modify
<cli> update <name> --dry-run # Test first
<cli> delete <name> --backup  # Backup first

# Common Patterns
<cli> list                    # Show all
<cli> create <name> [opts]    # Create new
<cli> update <name> [opts]    # Modify existing
<cli> delete <name>           # Remove

# Output Formats
<cli> list --json            # Machine readable
<cli> get <name> --verbose   # Detailed info

# Configuration
<cli> cmd --config work      # Named config
<cli> cmd --base             # Base config
<cli> cmd                    # Default (local)