Format-Specific Exploration Recipes

Format-Specific Exploration Recipes

Per-format commands for exploring structured data with dasel v3. Each section covers the format's unique characteristics and provides concrete commands.

Table of Contents

• JSON Exploration
• YAML Exploration
• TOML Exploration
• XML Exploration
• CSV Exploration
• HCL Exploration
• INI Exploration

JSON Exploration

JSON is dasel's native format. All operations work without caveats.

Discover Structure

# Top-level keys
dasel -f data.json 'keys($this)'

# Nested object keys
dasel -f data.json 'keys(config.database)'

Inspect Arrays of Objects

# Preview first element to understand object shape
dasel -f data.json 'users[0]'

# Keys of first element (reveals schema of array items)
dasel -f data.json 'keys(users[0])'

# Count elements
dasel -f data.json 'len(users)'

# Sample first 3 elements
dasel -f data.json 'users[0:3]'

Search Nested Objects

# Find all objects containing "email" at any depth
dasel -f data.json 'search(has("email"))'

# Find objects where "status" equals "active"
dasel -f data.json 'search(status == "active")'

# Combined predicate
dasel -f data.json 'search(has("id") && has("name"))'

Extract Specific Fields from Arrays

# Get all names from users array
dasel -f data.json 'users.map(name)'

# Get all unique roles
dasel -f data.json 'users.map(role)' | dasel -i json '$this...' | sort -u

Mixed-Type Detection

# Check type of ambiguous field
dasel -f data.json 'typeOf(config.port)'
# Returns: "int", "string", "float", etc.

# Check if field is array or object
dasel -f data.json 'typeOf(metadata)'

YAML Exploration

YAML supports anchors, multi-document files, and deep nesting common in Kubernetes and CI configs.

Discover Structure

# Top-level keys
dasel -f config.yaml 'keys($this)'

# Deeply nested config (common in Kubernetes)
dasel -f deployment.yaml 'keys(spec.template.spec)'

Deep Nesting Navigation

# Step through Kubernetes manifest
dasel -f deployment.yaml 'keys($this)'
# -> ["apiVersion", "kind", "metadata", "spec"]

dasel -f deployment.yaml 'keys(spec)'
# -> ["replicas", "selector", "template"]

dasel -f deployment.yaml 'spec.template.spec.containers[0].image'

Inspect Nested Arrays

# List container names in a pod spec
dasel -f deployment.yaml 'spec.template.spec.containers.map(name)'

# Count containers
dasel -f deployment.yaml 'len(spec.template.spec.containers)'

# Get all environment variable names from first container
dasel -f deployment.yaml 'spec.template.spec.containers[0].env.map(name)'

Recursive Key Search

# Find all keys named "image" at any depth
dasel -f deployment.yaml '..image'

# Find all objects with a "name" field
dasel -f deployment.yaml 'search(has("name"))'

TOML Exploration

TOML uses tables (sections) and arrays of tables. Common in Rust (Cargo.toml), Python (pyproject.toml), and Go configs.

Enumerate Tables

# Top-level tables and keys
dasel -f pyproject.toml 'keys($this)'

# Nested tables
dasel -f Cargo.toml 'keys(dependencies)'
dasel -f pyproject.toml 'keys(tool.ruff)'

Inspect Arrays of Tables

# pyproject.toml optional-dependencies or similar array sections
dasel -f Cargo.toml 'keys(bin[0])'
dasel -f Cargo.toml 'len(bin)'

Value Extraction

# Package metadata
dasel -f pyproject.toml 'project.name'
dasel -f pyproject.toml 'project.version'

# Dependency list
dasel -f pyproject.toml 'keys(project.dependencies)'

Type Checking

# Verify field types (TOML distinguishes int, float, string, bool, datetime)
dasel -f config.toml 'typeOf(server.port)'
dasel -f config.toml 'typeOf(server.debug)'

XML Exploration

XML has elements, attributes, and text content. Dasel represents these as nested objects.

Element Listing

# Top-level element (XML has single root)
dasel -f data.xml 'keys($this)'

# Child elements
dasel -f pom.xml 'keys(project)'
dasel -f pom.xml 'keys(project.dependencies)'

Inspect Repeated Elements

# Count dependency entries in Maven POM
dasel -f pom.xml 'len(project.dependencies.dependency)'

# First dependency
dasel -f pom.xml 'project.dependencies.dependency[0]'

Attribute Access

XML attributes are accessible as properties on the element. The exact representation depends on dasel's XML mapping. Inspect the element first:

# View full element to see attribute representation
dasel -f data.xml 'root.element[0]'

Recursive Search

# Find all elements with a specific child
dasel -f data.xml 'search(has("version"))'

CSV Exploration

CSV files are represented as arrays of objects (header row becomes keys).

Header Extraction

# Get column names from first row
dasel -f data.csv 'keys($this[0])'

Row Count

dasel -f data.csv 'len($this)'

Sample Rows

# First row (as object with column keys)
dasel -f data.csv '$this[0]'

# First 3 rows
dasel -f data.csv '$this[0:3]'

Column Sampling

# Extract single column values
dasel -f data.csv '$this.map(name)'

# Unique values in a column
dasel -f data.csv '$this.map(category)' | dasel -i json '$this...' | sort -u

Type Inspection

CSV values are typically strings. Check with:

dasel -f data.csv 'typeOf($this[0].age)'

HCL Exploration

HCL (HashiCorp Configuration Language) uses blocks with labels. Common in Terraform files.

Block Discovery

# Top-level block types
dasel -f main.tf 'keys($this)'
# -> ["resource", "variable", "output", "provider"]

Inspect Block Labels

# Resource types
dasel -f main.tf 'keys(resource)'

# Specific resource
dasel -f main.tf 'resource.aws_instance'
dasel -f main.tf 'keys(resource.aws_instance)'

Nested Block Inspection

# Terraform resource attributes
dasel -f main.tf 'resource.aws_instance.web'
dasel -f main.tf 'keys(resource.aws_instance.web)'

Variable Discovery

# List all variable names
dasel -f variables.tf 'keys(variable)'

# Get variable default value
dasel -f variables.tf 'variable.region.default'

INI Exploration

INI files have sections and key-value pairs. Common in systemd, PHP, Git config.

Section Listing

# List all sections
dasel -f config.ini 'keys($this)'

Key Listing Within Section

# Keys in a specific section
dasel -f config.ini 'keys(database)'
dasel -f config.ini 'keys(server)'

Value Extraction

dasel -f config.ini 'database.host'
dasel -f config.ini 'server.port'

Full Section Dump

# View all keys and values in a section
dasel -f config.ini 'database'

Cross-Format Tips

• Type ambiguity: CSV and INI store everything as strings. Use typeOf() to confirm before numeric operations.
• XML root: XML always has exactly one root element. keys($this) returns a single-element array.
• TOML datetimes: TOML natively supports datetime types. typeOf() reports these distinctly.
• HCL labels: HCL block labels become nested object keys. resource.aws_instance.web navigates type -> label -> label.
• Large files: Use search() instead of recursive descent (..) when you need predicate-based filtering, not exhaustive traversal.

References

• Dasel Query Syntax (fetched 2026-02-19)
• Dasel Functions Index (fetched 2026-02-19)
• Dasel Arrays and Slices (fetched 2026-02-19)