jq

JSON processor for filtering, transforming, and extracting data.

Quick Reference

jq '.field' file.json           # Extract field
jq '.[] | .name' file.json      # Extract from array
jq -r '.email' file.json        # Raw output (unquoted strings)
jq -s 'add' file1.json file2.json  # Merge arrays/objects
jq '.[] | select(.active)' file.json  # Filter elements
jq '.[] | {id, name}' file.json    # Pick fields

Key Flags

| Flag | Purpose | |------|----------| | -r | Output strings without quotes (raw mode) | | -R | Read input as plain text lines, not JSON | | -s | Slurp: read all inputs into single array | | -n | Start with null input (no file reading) | | -c | Compact output (single line) | | -e | Set exit status based on output | | --arg x v | Bind $x to string value v | | --argjson x j | Bind $x to JSON value j | | --sort-keys / -S | Sort object keys |

Common Patterns

Extract nested field: jq '.user.address.city'

Map over array: jq '.[] | {id, status}'

Filter + transform: jq '.items[] | select(.qty > 0) | .name'

Use variables: jq --arg role admin '.users[] | select(.role == $role)'

Pretty-print: jq '.' messy.json (3-space indent by default)