json-yaml

JSON & YAML Processing with jq and fy

Quick Reference

Action	Command
Pretty-print JSON	jq . file.json
Minify JSON	jq -c . file.json
Extract field	jq '.name' file.json
Extract raw string	jq -r '.name' file.json
Validate YAML	fy parse file.yaml
Format YAML	fy format -i file.yaml
Lint YAML	fy lint file.yaml
YAML to JSON	fy convert json file.yaml
JSON to YAML	fy convert yaml file.json
Validate JSON	jq empty file.json

jq Basics

Identity and Field Access

# Identity (pass-through, pretty-print)
cat data.json | jq .

# Access nested field
jq '.user.address.city' data.json

# Access array element
jq '.[0]' data.json
jq '.items[2]' data.json

# Access multiple fields (comma operator)
jq '.name, .age' data.json

# Optional field access (no error if missing)
jq '.missing?' data.json

String Interpolation

# Build strings from fields
jq -r '"Name: \(.name), Age: \(.age)"' data.json

# Use in filters
jq -r '.[] | "User \(.id): \(.email)"' users.json

Raw Output

# -r removes quotes from string output
jq -r '.name' data.json

# -R treats input as raw strings (not JSON)
echo "hello" | jq -R .

# --raw-output0 uses NUL separator (for xargs -0)
jq -r0 '.[]' list.json | xargs -0 -I{} echo "{}"

jq Filters

select — Filter by Condition

# Select objects matching condition
jq '.[] | select(.age > 30)' users.json

# Select by string match
jq '.[] | select(.name == "Alice")' users.json

# Select with contains
jq '.[] | select(.tags | contains(["admin"]))' users.json

# Select with test (regex)
jq '.[] | select(.email | test("@gmail\\.com$"))' users.json

# Select non-null values
jq '.[] | select(.address != null)' users.json

# Multiple conditions (and / or)
jq '.[] | select(.age > 25 and .status == "active")' users.json
jq '.[] | select(.role == "admin" or .role == "superadmin")' users.json

map — Transform Each Element