jq: JSON Data Extraction Tool

Use jq to extract specific fields from JSON files without loading entire file contents into context.

When to Use jq vs Read

Use jq when:

• Need specific field(s) from structured data file
• File is large (>50 lines) and only need subset
• Querying nested structures
• Filtering/transforming data
• Saves 80-95% context vs reading entire file

Just use Read when:

• File is small (<50 lines)
• Need to understand overall structure
• Making edits (need full context anyway)

Common File Types

JSON files where jq excels:

• package.json, tsconfig.json
• Lock files (package-lock.json, yarn.lock in JSON format)
• API responses
• Configuration files

Quick Examples

# Get version from package.json
jq -r .version package.json

# Get nested dependency version
jq -r '.dependencies.react' package.json

# List all dependencies
jq -r '.dependencies | keys[]' package.json

Core Principle

Extract exactly what is needed in one command - massive context savings compared to reading entire files.

Detailed Reference

For comprehensive jq patterns, syntax, and examples, load jq guide:

• Core patterns (80% of use cases)
• Real-world workflows
• Advanced patterns
• Pipe composition
• Error handling
• Integration with other tools