Dasel CLI Tool - Research Findings

Dasel CLI Tool - Research Findings

What Dasel Is and What Problem It Solves

Dasel (Data-Select) is a single-binary CLI tool and Go library for querying, modifying, and transforming structured data files. It solves the problem of needing separate tools (jq for JSON, yq for YAML, xmllint for XML) by providing one unified query syntax that works across all supported formats.

Primary use cases:

• Query values from structured config/data files in shell scripts
• Modify structured data files in-place without full-language scripts
• Convert between data formats (JSON to YAML, TOML to JSON, etc.)
• Recursive search through nested documents

Current stable version: v3.2.2 (released 2026-02-13). v3 is a major rewrite with revised syntax.

SOURCES:

• README: https://raw.githubusercontent.com/TomWright/dasel/master/README.md (fetched 2026-02-19)
• Docs: https://daseldocs.tomwright.me (fetched 2026-02-19)
• Releases: https://github.com/TomWright/dasel/releases (fetched 2026-02-19)
• CHANGELOG: https://raw.githubusercontent.com/TomWright/dasel/master/CHANGELOG.md (fetched 2026-02-19)

Supported Data Formats

Confirmed from cmd/dasel/main.go import list and documentation:

• JSON (json)
• YAML (yaml)
• TOML (toml)
• XML (xml)
• CSV (csv)
• HCL (hcl) — added in v3.0.0
• INI (ini) — added in v3.0.0

Format identifiers (used with -i/-o flags): json, yaml, toml, xml, csv, hcl, ini

Binary Release URL Pattern

Base URL pattern:

https://github.com/TomWright/dasel/releases/download/v{VERSION}/dasel_{platform}

Available Platforms (v3.2.2, 18 assets total)

Concrete Examples (v3.2.2)

https://github.com/TomWright/dasel/releases/download/v3.2.2/dasel_linux_amd64
https://github.com/TomWright/dasel/releases/download/v3.2.2/dasel_linux_arm64
https://github.com/TomWright/dasel/releases/download/v3.2.2/dasel_windows_amd64.exe
https://github.com/TomWright/dasel/releases/download/v3.2.2/dasel_darwin_arm64

Checksum Verification

Checksums are embedded directly in the GitHub release page per-asset. There is no separate SHA256SUMS file in releases. Each asset listing shows its sha256 hash inline.

Observed sha256 values for v3.2.2:

dasel_linux_amd64:    313f055bd8c7c59bb8a9cad863f0685769d6f8a93b5f9b9a0986c95c76513832
dasel_linux_arm64:    135ac22a599fca49d48af44bd5dfa83bccdd91cd813c34c018e3574f76e842e6
dasel_linux_arm32:    6c43ff668c8205465e5509f94f39095d1ba86275e2e9d2d85976abe4c0cf1083
dasel_linux_386:      06c4024d39494ea46bff086ff3622cb2e8a722c3f68b604fa0cf6cf03365e887
dasel_darwin_amd64:   cb064c256cc33e90ddc0630935bf6c6d640a34cf07eed5a47fdd365c13514239
dasel_darwin_arm64:   03f90053514080d57ed29b8558829e7e51f5ef8e62f25aa0029f67d2a9050e39
dasel_windows_amd64:  bf5ccd37700525f7b55592064cb74fa7fae3d86b76f8a7b7fc7ef2c237c9c2c0
dasel_windows_386:    299ae7e3c889f13f9e26ee323c50cb6a3395284b7d625c9c2fc43e1695d1c87f

To verify after download:

echo "313f055bd8c7c59bb8a9cad863f0685769d6f8a93b5f9b9a0986c95c76513832  dasel" | sha256sum -c

Checksums per release can be fetched dynamically via GitHub API:

curl -s https://api.github.com/repos/tomwright/dasel/releases/latest \
  | grep -E '"browser_download_url"|"sha256"'

Version Detection Command

dasel --version

To get the latest available version from GitHub API:

curl -s https://api.github.com/repos/tomwright/dasel/releases/latest \
  | grep '"tag_name"' \
  | cut -d'"' -f4

Install Instructions

Linux (64-bit amd64) — Auto-detect latest

curl -sSLf "$(curl -sSLf https://api.github.com/repos/tomwright/dasel/releases/latest \
  | grep browser_download_url \
  | grep linux_amd64 \
  | grep -v .gz \
  | cut -d'"' -f4)" -L -o dasel && chmod +x dasel
mv ./dasel /usr/local/bin/dasel

Linux (manual, pinned version)

VERSION=v3.2.2
ARCH=linux_amd64   # or linux_arm64, linux_arm32, linux_386
curl -sSLf "https://github.com/TomWright/dasel/releases/download/${VERSION}/dasel_${ARCH}" \
  -o /usr/local/bin/dasel
chmod +x /usr/local/bin/dasel

Windows (PowerShell)

$releases = curl -sSLf https://api.github.com/repos/tomwright/dasel/releases/latest
Invoke-WebRequest -Uri (($releases | ConvertFrom-Json).assets `
                    | Where-Object { $_.name -eq "dasel_windows_amd64.exe" } `
                    | Select-Object -ExpandProperty browser_download_url) `
                    -OutFile dasel.exe

Other install methods

• Homebrew (macOS/Linux): brew install dasel
• Docker: docker run -i --rm ghcr.io/tomwright/dasel:latest
• Go: go install github.com/tomwright/dasel/v3/cmd/dasel@master
• Scoop (Windows): scoop bucket add extras && scoop install dasel
• ASDF: asdf plugin add dasel && asdf install dasel <version>
• Mise: mise install dasel@<version>
• Nix: nix-env -iA nixpkgs.dasel

Core CLI Syntax (v3)

Flags

dasel [flags] [QUERY]

Key flags:
  -f, --file <path>     Input file path (reads stdin if omitted)
  -i, --input <format>  Input parser: json, yaml, toml, xml, csv, hcl, ini
  -o, --output <format> Output parser (defaults to input format)
  --root                Output the full document after modification
  -w, --write <path>    Write result to file (modifies in-place if same as -f)
  --var <name>=<value>  Pass variables into query (repeatable)
  --compact             Compact output (no pretty-printing)
  --colour              Enable colourised output
  --indent <string>     Set indentation string

Select (Query) — Read a Value

# From piped stdin
echo '{"foo": {"bar": "baz"}}' | dasel -i json 'foo.bar'
# Output: "baz"

# From file
dasel -f data.json 'foo.bar'
dasel -f config.yaml 'database.host'
dasel -f data.toml 'server.port'

Modify in Place — Write a Value

In v3, put and delete subcommands were removed. Modifications use assignment expressions with --root to output the full document:

# Update a value and output full document
echo '{"foo": {"bar": "baz"}}' | dasel -i json --root 'foo.bar = "newvalue"'

# Modify file in place
dasel -f config.yaml --root 'server.port = 9090' > config_new.yaml

# Numeric assignment
echo '{"count": 1}' | dasel -i json --root 'count = 42'

# Boolean assignment
echo '{"enabled": false}' | dasel -i json --root 'enabled = true'

Delete a Field

In v3, deletion is done by constructing a new object/map without the unwanted key:

# Remove a key using map spread (keeping all except the deleted key)
# Build new object without 'unwanted_key':
echo '{"keep": "yes", "remove": "no"}' | dasel -i json --root \
  '{ keep }'

Array Operations

# Access by index (zero-based)
echo '[10, 20, 30]' | dasel -i json '[1]'
# Output: 20

# Access last element
echo '[10, 20, 30]' | dasel -i json '[len($this)-1]'

# Range slice [start:end]
echo '[1,2,3,4,5]' | dasel -i json '[0:2]'
# Output: [1, 2, 3]

# Append to array
echo '[1,2,3]' | dasel -i json --root '[$this..., 4]'
# Output: [1, 2, 3, 4]

Batch Modify Array Elements — each

# Multiply all numbers by 2
echo '[1,2,3,4,5]' | dasel -i json --root 'each($this = $this*2)'
# Output: [2, 4, 6, 8, 10]

# Increment all integers
echo '[1,2,3]' | dasel -i json 'each($this = $this+1)'

Format Conversion

# JSON to YAML
cat data.json | dasel -i json -o yaml

# YAML to TOML
cat config.yaml | dasel -i yaml -o toml

# JSON to XML
cat data.json | dasel -i json -o xml

Recursive Descent (..)

# Find all values with key "name" at any depth
echo '{"user": {"name": "Alice"}}' | dasel -i json '..name'
# Output: ["Alice"]

# Get first element of every nested array
dasel -f data.json '..[0]'

# Get all values at any depth
dasel -f data.json '..*'

Search Function

More powerful than .. — supports arbitrary predicates:

# Find all objects that have a "name" key
dasel -f data.json 'search(has("name"))'

# Find nodes where value equals 42
dasel -f data.json 'search($this == 42)'

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

Filter and Map

# Filter array where active == true
echo '...' | dasel -i json 'users.filter(active == true)'

# Map: extract single field from array of objects
echo '...' | dasel -i json 'users.map(name)'

# Map with transformation
echo '[1,2,3]' | dasel -i json '[1,2,3].map($this * 2)'

Conditionals

# if/else expression
dasel -i json -f input.json '.foo.if(bar == "baz") { bong } else { qux }'

# Conditional with literal output
echo '{ "count": 7 }' | dasel -i json 'if(count > 5) { "many" } else { "few" }'

Variable Assignment (v3 feature)

# Multi-statement query with variables
dasel -f data.json '$activeUsers = users.filter(active == true); $activeUsers.map(name)'

Type Casting Functions

# typeOf: get type as string
echo '"hello"' | dasel -i json 'typeOf($this)'
# Output: "string"

# toString: convert to string
echo '123' | dasel -i json 'toString($this)'
# Output: "123"

# toInt: convert to integer
echo '"42"' | dasel -i json 'toInt($this)'
# Output: 42

# toFloat: convert to float
echo '"3.14"' | dasel -i json 'toFloat($this)'

Type strings returned by typeOf: "string", "array", "bool", "null", "int", "float"

Other Useful Functions

# len: length of array or string
echo '[1,2,3]' | dasel -i json 'len($this)'
# Output: 3

# has: check key/index exists (returns bool)
echo '{"foo": "bar"}' | dasel -i json 'has("foo")'
# Output: true

# join: join array elements into string
echo '["a","b","c"]' | dasel -i json 'join(",")'
# Output: "a,b,c"

# sum: sum numeric array
echo '[1,2,3,4,5]' | dasel -i json 'sum($this)'
# Output: 15

# keys: get map keys as array
echo '{"a": 1, "b": 2}' | dasel -i json 'keys($this)'

# reverse: reverse an array
echo '[1,2,3]' | dasel -i json 'reverse($this)'

v3 Breaking Changes from v2 (Important)

From CHANGELOG v3.0.0:

• put and delete subcommands removed. Modifications done inline in query with --root flag.
• Query/selector syntax revamped — v2 syntax is not compatible with v3.
• Go module path changed to github.com/tomwright/dasel/v3.
• CLI framework changed from Cobra to Kong.

If a plugin needs to support v2 as well, the put command was used in v2:

# v2 syntax (NOT v3):
dasel put string -f data.json -o - '.foo.bar' 'newvalue'
dasel delete -f data.json '.foo.bar'

Special Syntax Notes

$root and $this Variables

• $root — references the root document
• $this — references the current node (used inside each, map, filter, search)

Spread Operator

# Spread array into arguments
doSomething([1, 2, 3]...)  # equivalent to doSomething(1, 2, 3)

# Merge objects
{ {"firstName": "Tom"}..., "lastName": "Wright" }
# resolves to { "firstName": "Tom", "lastName": "Wright" }

# Output array elements as separate documents
[1, 2, 3]...
# 1
# 2
# 3

Multi-statement Queries (semicolon separator)

# Statements separated by semicolons; final statement is output
dasel -f data.json '$active = users.filter(active == true); $active.map(name)'

Comments in Queries

v3 supports comments in multi-statement queries (syntax not yet documented in official docs but noted in v3.0.0 release notes).

References

1. README (raw): https://raw.githubusercontent.com/TomWright/dasel/master/README.md (fetched 2026-02-19)
2. Installation docs: https://daseldocs.tomwright.me/getting-started/installation (fetched 2026-02-19)
3. Releases page: https://github.com/TomWright/dasel/releases (fetched 2026-02-19)
4. Release v3.2.2 assets: https://github.com/TomWright/dasel/releases/tag/v3.2.2 (fetched 2026-02-19)
5. CHANGELOG: https://raw.githubusercontent.com/TomWright/dasel/master/CHANGELOG.md (fetched 2026-02-19)
6. Query syntax docs: https://daseldocs.tomwright.me/syntax/query-syntax.md (fetched 2026-02-19)
7. Types/Literals: https://daseldocs.tomwright.me/syntax/types-literals.md (fetched 2026-02-19)
8. Recursive descent: https://daseldocs.tomwright.me/syntax/recursive-descent.md (fetched 2026-02-19)
9. Arrays/slices: https://daseldocs.tomwright.me/syntax/arrays-slices.md (fetched 2026-02-19)
10. Objects/maps: https://daseldocs.tomwright.me/syntax/objects-maps.md (fetched 2026-02-19)
11. Conditionals: https://daseldocs.tomwright.me/syntax/conditionals.md (fetched 2026-02-19)
12. Spread: https://daseldocs.tomwright.me/syntax/spread.md (fetched 2026-02-19)
13. Functions index: https://daseldocs.tomwright.me/functions (fetched 2026-02-19)
14. search(): https://daseldocs.tomwright.me/functions/search.md (fetched 2026-02-19)
15. each(): https://daseldocs.tomwright.me/functions/each.md (fetched 2026-02-19)
16. filter(): https://daseldocs.tomwright.me/functions/filter.md (fetched 2026-02-19)
17. map(): https://daseldocs.tomwright.me/functions/map.md (fetched 2026-02-19)
18. typeOf(): https://daseldocs.tomwright.me/functions/typeof.md (fetched 2026-02-19)
19. toString(): https://daseldocs.tomwright.me/functions/tostring.md (fetched 2026-02-19)
20. toInt(): https://daseldocs.tomwright.me/functions/toint.md (fetched 2026-02-19)
21. has(): https://daseldocs.tomwright.me/functions/has.md (fetched 2026-02-19)
22. join(): https://daseldocs.tomwright.me/functions/join.md (fetched 2026-02-19)
23. main.go (format parsers): https://github.com/TomWright/dasel/blob/master/cmd/dasel/main.go (fetched 2026-02-19)