Data Processing
Query, filter, and transform structured data (JSON, YAML, TOML) efficiently from the command line.
Tools
| Tool | Command | Use For |
|---|---|---|
| jq | jq '.key' file.json | JSON processing |
| yq | yq '.key' file.yaml | YAML/TOML processing |
jq Essentials
bash# Extract single field jq '.name' package.json # Extract nested field jq '.scripts.build' package.json # Extract from array jq '.dependencies[0]' package.json # Extract multiple fields jq '{name, version}' package.json # Navigate deeply nested jq '.data.users[0].profile.email' response.json # Filter by condition jq '.users[] | select(.active == true)' data.json # Transform each element jq '.users | map({id, name})' data.json # Count elements jq '.users | length' data.json # Raw string output jq -r '.name' package.json
yq Essentials
bash# Extract field yq '.name' config.yaml # Extract nested yq '.services.web.image' docker-compose.yml # List all keys yq 'keys' config.yaml # List all service names (Docker Compose) yq '.services | keys' docker-compose.yml # Get container images (K8s) yq '.spec.template.spec.containers[].image' deployment.yaml # Update value (in-place) yq -i '.version = "2.0.0"' config.yaml # TOML to JSON yq -p toml -o json '.' config.toml
Quick Reference
| Task | jq | yq |
|---|---|---|
| Get field | jq '.key' | yq '.key' |
| Array element | jq '.[0]' | yq '.[0]' |
| Filter array | jq '.[] | select(.x)' | yq '.[] | select(.x)' |
| Transform | jq 'map(.x)' | yq 'map(.x)' |
| Count | jq 'length' | yq 'length' |
| Keys | jq 'keys' | yq 'keys' |
| Pretty print | jq '.' | yq '.' |
| Compact | jq -c | yq -o json -I0 |
| Raw output | jq -r | yq -r |
| In-place edit | - | yq -i |
When to Use
- Reading package.json dependencies
- Parsing Docker Compose configurations
- Analyzing Kubernetes manifests
- Processing GitHub Actions workflows
- Extracting data from API responses
- Filtering large JSON datasets
- Config file manipulation
- Data format conversion
Additional Resources
For complete pattern libraries, load:
./references/jq-patterns.md- Arrays, filtering, transformation, aggregation, output formatting./references/yq-patterns.md- Docker Compose, K8s, GitHub Actions, TOML, YAML modification./references/config-files.md- package.json, tsconfig, eslint/prettier patterns
