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jq is a lightweight and flexible command-line JSON processor. Parse, filter, transform, and manipulate JSON data with ease. Essential for API responses, configuration files, and data processing pipelines.

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Basic Usage

• jq '.' file.json - Pretty print JSON

• jq '.key' file.json - Extract value by key

• echo '{"key":"value"}' | jq '.' - Pipe JSON

• jq -r '.key' file.json - Raw output (no quotes)

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Filtering

• jq '.key' - Get value

• jq '.key1.key2' - Nested access

• jq '.[]' - Array iteration

• jq '.[0]' - First element

• jq '.[-1]' - Last element

• jq '.[:3]' - First 3 elements

• jq '.[] | select(.key == "value")' - Filter objects

• jq '.[] | select(.key > 10)' - Numeric comparison

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Object Operations

• jq '.key1, .key2' - Multiple keys

• jq '{newkey: .oldkey}' - Rename key

• jq '. + {newkey: "value"}' - Add key

• jq 'del(.key)' - Delete key

• jq 'keys' - List all keys

• jq 'has("key")' - Check if key exists

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Array Operations

• jq '.array[]' - Iterate array

• jq '.array | length' - Array length

• jq '.array | .[0:3]' - Slice array

• jq '.array + ["new"]' - Append element

• jq '.array | map(.key)' - Extract key from objects

• jq '.array | sort' - Sort array

• jq '.array | unique' - Remove duplicates

• jq '.array | reverse' - Reverse array

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String Operations

• jq '.key | length' - String length

• jq '.key | split(",")' - Split string

• jq '.key | startswith("prefix")' - Check prefix

• jq '.key | endswith("suffix")' - Check suffix

• jq '.key | contains("substring")' - Check substring

• jq '.key | upper' - Uppercase

• jq '.key | lower' - Lowercase

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Output Options

• -r / --raw-output - Raw string output

• -c / --compact-output - Compact JSON

• -s / --slurp - Read entire input as array

• -n / --null-input - Null input

• --tab - Use tabs for indentation

• --indent N - Indentation level

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Common Examples

Pretty Print

cat data.json | jq '.'

Format JSON nicely.

Extract Field

jq '.name' users.json

Get name field from objects.

Filter Array

jq '.[] | select(.status == "active")' users.json

Filter objects by condition.

Extract Multiple Fields

jq '{name: .name, id: .id}' users.json

Create new object with selected fields.

Array to CSV

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

Convert JSON array to CSV.

Count Elements

jq '.items | length' data.json

Count items in array.

Sum Values

jq '[.[] | .price] | add' items.json

Sum numeric values.

Group By

jq 'group_by(.category) | map({category: .[0].category, count: length})' items.json

Group objects by field.

Flatten Nested

jq '.users[].name' data.json

Extract from nested arrays.

Merge Objects

jq '. + {timestamp: now}' data.json

Add field to object.

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Tips

• Use -r for raw string output in scripts

• Use .[] to iterate arrays and objects

• Use select() for filtering

• Use map() to transform arrays

• Combine filters with | (pipe)

• Use @csv, @tsv for formatted output

• Essential for API response processing

• Great for configuration file manipulation