Jq JSON Processor

jq JSON Processor

Process, filter, and transform JSON data with jq.

When to use

• Parsing, filtering, or transforming JSON from commands, files, or API responses — slicing, reshaping, or validating JSON output.

Quick Examples

Basic filtering

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

# Multiple fields
echo '{"name":"Alice","age":30}' | jq '{name: .name, age: .age}'

# Array indexing
echo '[1,2,3,4,5]' | jq '.[2]'
# Output: 3

Working with arrays

# Map over array
echo '[{"name":"Alice"},{"name":"Bob"}]' | jq '.[].name'
# Output: "Alice" "Bob"

# Filter array
echo '[1,2,3,4,5]' | jq 'map(select(. > 2))'
# Output: [3,4,5]

# Length
echo '[1,2,3]' | jq 'length'
# Output: 3

Common operations

# Pretty print JSON
cat file.json | jq '.'

# Compact output
cat file.json | jq -c '.'

# Raw output (no quotes)
echo '{"name":"Alice"}' | jq -r '.name'
# Output: Alice

# Sort keys
echo '{"z":1,"a":2}' | jq -S '.'

Advanced filtering

# Select with conditions
jq '[.[] | select(.age > 25)]' people.json

# Group by
jq 'group_by(.category)' items.json

# Reduce
echo '[1,2,3,4,5]' | jq 'reduce .[] as $item (0; . + $item)'
# Output: 15

Working with files

# Read from file
jq '.users[0].name' users.json

# Multiple files
jq -s '.[0] * .[1]' file1.json file2.json

# Modify and save
jq '.version = "2.0"' package.json > package.json.tmp && mv package.json.tmp package.json

Common Use Cases

Extract specific fields from API response:

curl -s https://api.github.com/users/octocat | jq '{name: .name, repos: .public_repos, followers: .followers}'

Convert CSV-like data:

jq -r '.[] | [.name, .email, .age] | @csv' users.json

Debug API responses:

curl -s https://api.example.com/data | jq '.'

Tips

• Use -r for raw string output (removes quotes)
• Use -c for compact output (single line)
• Use -S to sort object keys
• Use --arg name value to pass variables
• Pipe multiple jq operations: jq '.a' | jq '.b'

Documentation

Full manual: https://jqlang.github.io/jq/manual/ Interactive tutorial: https://jqplay.org/