dasel

Dasel (short for data-selector) allows you to query and modify data structures using selector strings.

Usage

You can import dasel as a package and use it in your applications, or you can use a pre-built binary to modify files from the command line.

Import

As with any other go package, just use go get.

go get github.com/tomwright/dasel/cmd/dasel

Command line

You can go get the main package and go should automatically build and install dasel for you.

go get github.com/tomwright/dasel/cmd/dasel

Alternatively you can download a compiled executable from the latest release: This one liner should work for you - be sure to change the targeted release executable if needed. It currently targets dasel_linux_amd64.

curl -s https://api.github.com/repos/tomwright/dasel/releases/latest | grep browser_download_url | grep linux_amd64 | cut -d '"' -f 4 | wget -qi - && mv dasel_linux_amd64 dasel && chmod +x dasel

Support data types

Dasel attempts to find the correct parser for the given file type, but if that fails you can choose which parser to use with the -p or --parser flag.

• YAML - -p yaml
• JSON - -p json

Selectors

Selectors are used to define a path through a set of data. This path is usually defined as a chain of nodes.

A selector is made up of different parts separated by a dot ., each part being used to identify the next node in the chain.

The following YAML data structure will be used as a reference in the following examples.

name: Tom
preferences:
  favouriteColour: red
colours:
- red
- green
- blue
colourCodes:
- name: red
  rgb: ff0000
- name: green
  rgb: 00ff00
- name: blue
  rgb: 0000ff

Property

Property selectors are used to reference a single property of an object.

Just use the property name as a string.

$ dasel select -f ./tests/assets/example.yaml -s "name"
Tom

• name == Tom

Child Elements

Just separate the child element from the parent element using a .:

$ dasel select -f ./tests/assets/example.yaml -s "preferences.favouriteColour"
red

• preferences.favouriteColour == red

Index

When you have a list, you can use square brackets to access a specific item in the list by its index.

$ dasel select -f ./tests/assets/example.yaml -s "colours.[1]"
green

• colours.[0] == red
• colours.[1] == green
• colours.[2] == blue

Next Available Index - WIP

Next available index selector is used when adding to a list of items. It allows you to append to a list.

• colours.[]

Dynamic

Dynamic selectors are used with lists when you don't know the index of the item, but instead know the value of a property of an object within the list.

Look ups are defined in brackets. You can use multiple dynamic selectors within the same part to perform multiple checks.

$ dasel select -f ./tests/assets/example.yaml -s ".colourCodes.(name=red).rgb"
ff0000

$ dasel select -f ./tests/assets/example.yaml -s ".colourCodes.(name=blue)(rgb=0000ff)"
map[name:blue rgb:0000ff]

• .colourCodes.(name=red).rgb == ff0000
• .colourCodes.(name=green).rgb == 00ff00
• .colourCodes.(name=blue).rgb == 0000ff
• .colourCodes.(name=blue)(rgb=0000ff).rgb == 0000ff