Scripting

Scripting Skill

Write automation scripts and utility programs.

When to Use

Use this skill when the user wants to:

• Create shell scripts (bash, zsh)
• Write automation utilities
• Build command-line tools
• Implement data processing scripts
• Create configuration scripts
• Set up automation workflows

Script Types

Shell Scripts

• Bash scripts: Unix/Linux automation
• Zsh scripts: macOS automation
• PowerShell: Windows automation

Automation Scripts

• Data processing: Extract, transform, load
• File operations: Move, copy, organize files
• Scheduled tasks: Cron jobs, scheduled tasks
• System administration: Backup, cleanup, monitoring

CLI Tools

• Argument parsing: Handle CLI arguments
• Option parsing: Flags and options
• Output formatting: Console output
• Error handling: User-friendly errors

Shell Script Best Practices

Shebang

#!/usr/bin/env bash
#!/bin/zsh

Variable Naming

# Use descriptive names
user_name="alice"
backup_dir="/tmp/backup"
max_retries=3

Error Handling

# Check command success
if ! command -v curl &> /dev/null; then
  echo "Error: curl is required"
  exit 1
fi

# Trap errors
set -e  # Exit on error
set -u  # Exit on undefined variable
set -o pipefail  # Fail on pipe failure

Input Validation

# Check arguments
if [[ $# -lt 1 ]]; then
  echo "Usage: $0 <input_file>"
  exit 1
fi

# Validate input
input_file="$1"
if [[ ! -f "$input_file" ]]; then
  echo "Error: File not found: $input_file"
  exit 1
fi

User Interaction

# Ask for confirmation
read -p "Continue? [y/N] " confirm
if [[ ! "$confirm" =~ ^[Yy]$ ]]; then
  echo "Cancelled"
  exit 0
fi

# Read user input
read -p "Enter your name: " username

Python Scripting

Input Validation

import argparse

def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument('--input', required=True, help='Input file')
    parser.add_argument('--output', help='Output file')
    parser.add_argument('--verbose', action='store_true')
    return parser.parse_args()

Error Handling

try:
    with open('data.json', 'r') as f:
        data = json.load(f)
except FileNotFoundError:
    print("Error: File not found")
    sys.exit(1)
except json.JSONDecodeError as e:
    print(f"Error: Invalid JSON: {e}")
    sys.exit(1)

Script Entry Point

if __name__ == '__main__':
    main()

Node.js Scripting

CLI Tools with Commander

const { Command } = require('commander');
const program = new Command();

program
  .name('my-tool')
  .description('A utility tool')
  .version('1.0.0')
  .option('-v, --verbose', 'Verbose output')
  .parse();

const options = program.opts();
console.log('Verbose:', options.verbose);

Data Processing Scripts

Reading and Writing

# Read from file
while IFS= read -r line; do
  echo "$line"
done < input.txt

# Write to file
echo "Line 1" > output.txt
echo "Line 2" >> output.txt

Transformation

# Process lines
cat input.txt | while read line; do
  # Process each line
  echo "Processed: $line"
done

Automation Workflows

Scheduled Tasks

# Cron job
0 2 * * * /path/to/script.sh >> /var/log/script.log 2>&1

Processing Data

# Process CSV
while IFS=, read -r col1 col2 col3; do
  echo "Processing: $col1, $col2"
done < data.csv

File Operations

# Copy with progress
cp -v source.txt dest.txt

# Find and process files
find . -type f -name "*.log" -exec ./process.sh {} \;

Deliverables

• Complete scripts with error handling
• Usage documentation
• Examples and usage patterns
• Test scripts
• Configuration files

Quality Checklist

• Shebang is correct
• Exit codes are proper
• Error messages are clear
• Input validation included
• Comments explain complex logic
• Scripts are executable
• Documentation is clear
• Works on target platforms