Jq

jq - JSON Processor

When to use this skill

Parse and manipulate JSON data from command line. Extract fields, filter arrays, transform structures, or format JSON output.

Quick start

# Pretty print JSON
echo '{"name":"John","age":30}' | jq '.'

# Extract field
echo '{"name":"John","age":30}' | jq '.name'

# Filter array
echo '[{"name":"John"},{"name":"Jane"}]' | jq '.[0]'

# Transform
echo '{"name":"John"}' | jq '{user: .name}'

Common commands

# Basic queries
jq '.'                          # Pretty print
jq '.field'                     # Extract field
jq '.field.nested'              # Nested field
jq '.[]'                        # Array elements

# Filtering
jq '.[] | select(.age > 25)'    # Filter array
jq 'map(select(.active))'       # Filter with map
jq '.[] | select(.name == "John")'  # Exact match

# Transformation
jq '{name: .user, id: .userId}' # Reshape object
jq 'map({name, age})'           # Extract fields from array
jq '.[] | {name, age}'          # Transform array elements

# Array operations
jq 'length'                     # Array/object length
jq 'keys'                       # Object keys
jq 'sort_by(.age)'              # Sort array
jq 'group_by(.type)'            # Group array

# Output formats
jq -r '.name'                   # Raw output (no quotes)
jq -c '.'                       # Compact output
jq -S '.'                       # Sort keys

Common patterns

# Parse API response
curl -s https://api.example.com/users | jq '.data[].name'

# Extract from file
jq '.users[] | select(.active)' users.json

# Multiple filters
jq '.[] | select(.age > 25) | .name' data.json

# Combine fields
jq '.[] | "\(.name) is \(.age) years old"' data.json

# Count items
jq '[.[] | select(.status == "active")] | length' data.json

Common issues

• Parse error: Input must be valid JSON
• Null values: Use // "default" for null handling
• Array vs object: Use .[] for arrays, .field for objects
• Quotes in output: Use -r flag for raw output without quotes

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: geronimo-iia
• Source: geronimo-iia/agent-skills
• License: MIT
• Homepage: https://geronimo-iia.github.io/agent-skills/

Install and usage instructions live in the source repository linked above.