jq - Command-Line JSON Processor | Hexmos DevTools - cmd Cheatsheets

jq is a lightweight and flexible command-line JSON processor. It allows you to easily filter, transform, and manipulate JSON data directly from your terminal.

jq Command Examples

Basic Usage and Pretty-Printing

To output a JSON file in a human-readable, pretty-print format, you can use:

jq '.' file.json

This command reads the JSON from file.json and outputs it with indentation.

Extracting Data

You can extract specific fields or elements from JSON data:

Extract a specific field: jq '.fieldName' file.json
Extract a specific element from an array by index: jq '.[index]' file.json
Select multiple fields: jq '{field1: .field1, field2: .field2}' file.json
Query nested JSON data: jq '.outerField.innerField' file.json

Array and Object Manipulation

jq excels at working with arrays and objects:

Output all elements from arrays: jq .[]
Count the number of elements in an array: jq '.arrayName | length' file.json
Apply a function to each element in an array: jq '.arrayName[] | .fieldName' file.json
Concatenate fields: jq '.field1 + " " + .field2' file.json
Group by a particular field: jq 'group_by(.fieldName)' file.json
Sort JSON objects by field: jq 'sort_by(.fieldName)' file.json
Find unique values: jq 'unique' file.json
Delete a field: jq 'del(.fieldName)' file.json
Concatenate arrays: jq 'add'
Flatten an array: jq 'flatten'
Create a range of numbers: jq '[range(2;4)]'
Sort an array of basic type: jq 'sort'
Sort an array of objects: jq 'sort_by(.foo)'
Sort lines of a file: jq --slurp '. | sort | .[]'
Minimum value of an array: jq 'min'
Remove duplicates: jq 'unique'
Reverse an array: jq 'reverse'

Filtering and Conditional Logic

Filter JSON objects based on specific conditions:

jq 'select(.fieldName == "value")' file.json

Filter a list of objects:

jq 'map(select(.name == "foo"))'

Input and Output Formats

jq supports various input and output formats:

Parse JSON from stdin: cat file.json | jq '.fieldName'
Load JSON from URL: curl -s "http://example.com/file.json" | jq '.fieldName'
Output compact JSON without whitespace: jq -c '.' file.json
Combine data from two JSON files: jq -s '.[0] + .[1]' file1.json file2.json
Read JSON objects from a file into an array: jq --slurp

Converting arbitrary data to JSON:

jq -r '(map(keys) | add | unique | sort) as $cols \
                                | .[] as $row | $cols | map($row[.]) | @csv'

Converting to CSV:
```
jq '.[] | [.foo, .bar] | @csv' -r
```

Parsing JSON within values:

jq 'with_entries(.value |= fromjson)' --sort-keys

Serializing JSON within values:

jq 'with_entries(.value |= tojson)' --sort-keys

jq in Shell Scripts

Integrate jq into your shell scripts for powerful JSON processing:

URL Encode something: date | jq -sRr @uri

Create proper JSON from shell variables:

jq -n --arg foobaz "$FOOBAZ" '{"foobaz":$foobaz}'

Fill environment variables from JSON object keys:
```
export $(jq -r '@sh "FOO=\(.foo) BAZ=\(.baz)"')
```

jq - Command-Line JSON Processor