jq

# jq Command-line JSON processor for extracting, filtering, and transforming JSON. ## Installation **macOS / Linux (Homebrew):** ```bash brew install jq ``` **All platforms:** See [jqlang.org/download](https://jqlang.org/download/) for packages, binaries, and build instructions. ## Usage ```bash jq '[filter]' [file.json] cat file.json | jq '[filter]' ``` ## Quick Reference ```bash .key # Get key .a.b.c # Nested access .[0] # First element .[] # Iterate array .[] | select(.x > 5) # Filter {a: .x, b: .y} # Reshape . + {new: "val"} # Add field del(.key) # Remove field length # Count [.[] | .x] | add # Sum keys # List keys unique # Dedupe array group_by(.x) # Group ``` ## Flags `-r` raw output (no quotes) · `-c` compact · `-s` slurp into array · `-S` sort keys ## Examples ```bash jq '.users[].email' data.json # Extract emails jq -r '.name // "default"' data.json # With fallback jq '.[] | select(.active)' data.json # Filter active jq -s 'add' *.json # Merge files jq '.' file.json # Pretty-print ```