jq is like sed for JSON data - you can use it to slice and filter and map and transform structured data with the same ease that sed, awk, grep and friends let you play with text.
jq is written in portable C, and it has zero runtime dependencies. You can download a single binary, scp it to a far away machine of the same type, and expect it to work.
# Basic Selection
echo '{"name": "John", "age": 30, "city": "New York"}' | jq '.name'
# Output: "John"
# Filtering Arrays
echo '[{"name": "Alice", "age": 25}, {"name": "Bob", "age": 32}]' | jq '.[] | select(.age > 30) | .name'
# Output: "Bob"
# Conditional Statements
echo '{"name": "Sam", "age": 22}' | jq 'if .age >= 21 then "Can drink" else "Cannot drink" end'
# Output: "Can drink"
# Reading from a File
jq '.users[] | .name' data.json
# Combining Filters
echo '{"people": [{"name": "Alex", "age": 35}, {"name": "Eva", "age": 28}]}' | jq '.people[] | select(.age > 30) | .name'
# Output: "Alex"
# Parsing JSON from a URL
curl -s https://api.example.com/data | jq '.results[0].name'
# Sorting Arrays
echo '[3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]' | jq 'sort'
# Output: [1,1,2,3,3,4,5,5,5,6,9]
# Formatting Output
echo '{"name": "Tom", "age": 40}' | jq -r '"Name: \(.name), Age: \(.age)"'
# Output: Name: Tom, Age: 40
# Adding a New Field
echo '{"name": "Alice", "age": 25}' | jq '. | .city = "New York"'
# Output: {"name": "Alice", "age": 25, "city": "New York"}
# Changing Field Values
echo '{"name": "Bob", "age": 32}' | jq '. | .age = .age + 5'
# Output: {"name": "Bob", "age": 37}
# Filtering and Mapping
echo '{"people": [{"name": "Charlie", "age": 30}, {"name": "David", "age": 28}]}' | jq '.people[] | {full_name: (.name + " Smith"), doubled_age: (.age * 2)}'
# Output:
# {"full_name": "Charlie Smith", "doubled_age": 60}
# {"full_name": "David Smith", "doubled_age": 56}
# Array Transformation
echo '[1, 2, 3, 4, 5]' | jq 'map(. * 2)'
# Output: [2, 4, 6, 8, 10]
# String Concatenation
echo '{"first_name": "John", "last_name": "Doe"}' | jq '. | .full_name = .first_name + " " + .last_name'
# Output: {"first_name": "John", "last_name": "Doe", "full_name": "John Doe"}
# Conditional Transformation
echo '{"value": 15}' | jq '. | if .value > 10 then .status = "High" else .status = "Low" end'
# Output: {"value": 15, "status": "High"}