tools-only Data Exploration with Dasel v3
Activate this skill when:
- Exploring unfamiliar structured data files (config, API responses, datasets)
- Discovering the schema or shape of a document before modifying it
- Investigating nested config structures (Kubernetes manifests, CI pipelines, package files)
- Sampling large arrays or deeply nested objects to understand content
- Identifying data types before transformation or extraction
Supported Formats
Dasel auto-detects format from file extension. Override with -i <format> when reading from stdin or when extension is ambiguous.
Format identifiers: json, yaml, toml, xml, csv, hcl, ini
Universal Exploration Workflow
Follow this sequence when encountering an unknown structured data file. Each step narrows scope.
Step 1 — Format Detection
Dasel infers format from file extension. For stdin or non-standard extensions, specify explicitly:
cat mystery_file | dasel -i json 'keys($this)'
Step 2 — Top-Level Keys
dasel -f config.yaml 'keys($this)'
Output: array of top-level key names. This is always the first exploration command.
Step 3 — Structure Preview
For small files (configs, manifests), dump the full document:
dasel -f config.yaml
For large files, skip to Step 4.
Step 4 — Nested Key Discovery
Navigate level by level:
dasel -f config.yaml 'server'
dasel -f config.yaml 'keys(server)'
dasel -f config.yaml 'keys(server.logging)'
Recursive key discovery across all depths:
dasel -f config.yaml '..keys($this)'
Step 5 — Array Sampling
Preview first few elements without loading entire array:
dasel -f data.json 'items[0:3]'
Single element inspection:
dasel -f data.json 'items[0]'
Step 6 — Type Inspection
Determine the type of any node:
dasel -f data.json 'typeOf(settings)'
dasel -f data.json 'typeOf(items[0].count)'
Return values: "string", "array", "bool", "null", "int", "float"
Step 7 — Value Extraction
Once path is known, extract specific values:
dasel -f config.yaml 'database.connection.host'
dasel -f data.json 'users[0].email'
Exploration Patterns
Breadth-First Exploration
Start at root, enumerate keys at each level before going deeper:
dasel -f file.json 'keys($this)' # Level 0
dasel -f file.json 'keys(metadata)' # Level 1
dasel -f file.json 'keys(metadata.labels)' # Level 2
Search-Based Exploration (Large Files)
When the file is too large for manual traversal, use search() with predicates:
# Find all objects containing a specific key
dasel -f data.json 'search(has("email"))'
# Find all objects with both "id" and "name" keys
dasel -f data.json 'search(has("id") && has("name"))'
# Find nodes where a value matches
dasel -f data.json 'search($this == 42)'
Count Elements
dasel -f data.json 'len(items)'
dasel -f data.json 'len(keys($this))'
Unique Value Discovery
Extract a field from all array elements, then deduplicate in shell:
dasel -f data.json 'items.map(category)' | dasel -i json '$this...' | sort -u
Recursive Descent
Find all values for a key name at any depth:
dasel -f data.json '..name'
Get first element of every nested array:
dasel -f data.json '..[0]'
Format-Specific Recipes
For detailed per-format exploration commands, see Format-Specific Recipes.
References
- Dasel v3 Documentation (fetched 2026-02-19)
- Dasel Functions Index (fetched 2026-02-19)
- Dasel GitHub Repository (fetched 2026-02-19)