jq

Basic Operations

Pretty Print

jq '.' [file]

Compact Output

jq -c '.' [file]

Raw Output (No Quotes)

jq -r '.' [file]

Selecting Fields

Single Field

jq '.name' [file]

Nested Field

jq '.user.name' [file]

Multiple Fields

jq '.name, .age' [file]

Create Object with Selected Fields

jq '{name: .name, age: .age}' [file]

Array Operations

Get Array Length

jq '.items | length' [file]

First Element

jq '.items[0]' [file]

Last Element

jq '.items[-1]' [file]

Slice Array

jq '.items[2:5]' [file]

All Elements

jq '.items[]' [file]

Iterate and Extract Field

jq '.items[].name' [file]

Filtering

Select by Condition

jq '.items[] | select(.age > 18)' [file]

Filter by String Match

jq '.items[] | select(.name == "John")' [file]

Contains

jq '.items[] | select(.tags | contains(["linux"]))' [file]

Not Null

jq '.items[] | select(.email != null)' [file]

Mapping

Map Array

jq '.items | map(.name)' [file]

Transform Values

jq '.items | map({name: .name, uppercase: (.name | ascii_upcase)})' [file]

Map with Select

jq '.items | map(select(.active == true))' [file]

Sorting

Sort Array

jq '.items | sort' [file]

Sort by Field

jq '.items | sort_by(.age)' [file]

Reverse Sort

jq '.items | sort_by(.age) | reverse' [file]

Grouping

Group By Field

jq 'group_by(.category)' [file]

Unique Values

jq '.items | map(.category) | unique' [file]

Aggregation

Min/Max

jq '.items | map(.age) | min' [file]
jq '.items | map(.age) | max' [file]

Sum

jq '.items | map(.price) | add' [file]

Average

jq '.items | map(.age) | add / length' [file]

Conditionals

If-Then-Else

jq '.items[] | if .age >= 18 then "adult" else "minor" end' [file]

Ternary

jq '.items[] | .status = (if .active then "on" else "off" end)' [file]

String Operations

Concatenate

jq '.first_name + " " + .last_name' [file]

Split String

jq '.email | split("@")' [file]

Replace

jq '.text | gsub("old"; "new")' [file]

To Uppercase

jq '.name | ascii_upcase' [file]

To Lowercase

jq '.name | ascii_downcase' [file]

Object Manipulation

Add Field

jq '. + {new_field: "value"}' [file]

Delete Field

jq 'del(.field_name)' [file]

Get Keys

jq 'keys' [file]

Get Values

jq 'values' [file]

Merge Objects

jq '. * {override: "value"}' [file]

Type Conversion

To String

jq '.age | tostring' [file]

To Number

jq '.id | tonumber' [file]

To Array

jq '. | to_entries' [file]

From Array

jq 'from_entries' [file]

Input/Output

Read from stdin

echo '{"name":"John"}' | jq '.name'

Multiple JSON Documents

jq -s '.' file1.json file2.json

Write to File

jq '.' input.json > output.json

Tab-Separated Values

jq -r '.items[] | [.name, .age] | @tsv' [file]

CSV Output

jq -r '.items[] | [.name, .age] | @csv' [file]

Advanced Examples

Extract Nested Array Values

jq '.users[].orders[].id' [file]

Flatten Array

jq '[.[] | .items[]]' [file]

Recursive Descent

jq '.. | .email? | select(. != null)' [file]

Complex Filter

jq '.items[] | select(.price > 100 and .available == true) | {name, price}' [file]

Group and Count

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

Working with APIs

Fetch and Parse

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

Extract Field from API Response

curl -s https://api.github.com/users/github | jq '.name'

Filter and Format

curl -s https://api.example.com/users | jq '.[] | select(.active) | .email'

Common Use Cases

Pretty Print JSON

cat [file] | jq '.'

Extract All Email Addresses

jq '.users[].email' [file]

Count Items

jq '.items | length' [file]

Get Unique Tags

jq '[.items[].tags[]] | unique' [file]

Find by ID

jq '.items[] | select(.id == 123)' [file]

Convert to CSV

jq -r '.items[] | [.id, .name, .email] | @csv' [file]

Validate JSON

jq empty [file] && echo "Valid JSON" || echo "Invalid JSON"

Tips

• Use -r for raw output (without quotes)
• Use -c for compact output
• Use -s to slurp multiple JSON objects into array
• Pipe through jq '.' to validate JSON
• Use select() for filtering
• Combine with curl for API data processing