Getting Started ​

The fx utility operates in two primary modes: a reducer and an interactive viewer.

Quick Start ​

To initiate the interactive mode, pipe a JSON into fx:

$ curl ... | fx

$ curl ... | fx

Alternatively, specify the filename directly:

$ fx data.json

$ fx data.json

JSON Processing ​

$ cat file.json | npx fx .field

$ cat file.json | npx fx .field

$ cat file.json | deno run -A npm:fx .field

$ cat file.json | deno run -A npm:fx .field

In fx, arguments are treated as JavaScript functions. Input data is passed sequentially through each provided function:

echo '{"name": "world"}' | fx 'x => x.name' 'x => `Hello, ${x}!`'

echo '{"name": "world"}' | fx 'x => x.name' 'x => `Hello, ${x}!`'

For easier access to input data:

• Use this or x to reference the input.
• Start expressions with . to avoid using the x => x notation.

echo '{"name": "world"}' | fx '.name' '`Hello, ${this}!`'

echo '{"name": "world"}' | fx '.name' '`Hello, ${this}!`'

You can also utilize standard JavaScript functions:

echo '{"name": "world"}' | fx 'Object.keys'

echo '{"name": "world"}' | fx 'Object.keys'

Advanced Usage ​

Stream Processing ​

fx can handle a stream of JSON objects and apply arguments to each object:

echo '{"name": "hello"}\n{"name": "world"}' | fx '.name'

echo '{"name": "hello"}\n{"name": "world"}' | fx '.name'

For collective processing of a JSON stream as a single array, use the --slurp or -s flag:

echo '{"name": "hello"}\n{"name": "world"}' | fx --slurp '.map(x => x.name)' '.join(", ")'

echo '{"name": "hello"}\n{"name": "world"}' | fx --slurp '.map(x => x.name)' '.join(", ")'

Non-JSON Data ​

For non-JSON content, use the --raw or -r flag:

ls | fx -r '[x, x.includes(".md")]'

ls | fx -r '[x, x.includes(".md")]'

Combine --raw and --slurp (or -rs) to process as a single string array:

ls | fx -rs '.filter(x => x.includes(".md"))'

ls | fx -rs '.filter(x => x.includes(".md"))'

Utilize the skip symbol in fx to skip printing certain results:

ls | fx -r '.includes(".md") ? this : skip'

ls | fx -r '.includes(".md") ? this : skip'

Built-in Functions ​

fx comes equipped with several useful functions: uniq, sort, groupBy, chunk, zip.

cat file.json | fx 'uniq' 'sort' 'groupBy(x => x.name)'

cat file.json | fx 'uniq' 'sort' 'groupBy(x => x.name)'

fx is also promise-compatible:

echo '"https://medv.io/*"' | fx 'fetch' '.text()'

echo '"https://medv.io/*"' | fx 'fetch' '.text()'

Syntactic Sugar ​

fx provides shortcuts for commonly-used operations:

• Use a shortcut for the map function:

curl https://api.github.com/repos/antonmedv/fx/commits | fx 'map(.commit.message)'

curl https://api.github.com/repos/antonmedv/fx/commits | fx 'map(.commit.message)'

• There's a special notation for the flatMap function:

curl https://api.github.com/repos/kubernetes/kubernetes/issues | fx '.[].labels[].name'

curl https://api.github.com/repos/kubernetes/kubernetes/issues | fx '.[].labels[].name'

Configuration: .fxrc.js ​

fx can recognize the .fxrc.js file, either in the current directory or home directory. Here's how you can define custom functions:

global.myFunction = x => x + 1

global.myFunction = x => x + 1

Invoke your custom function in fx:

echo '1' | fx 'myFunction'

echo '1' | fx 'myFunction'

Streaming Mode ​

fx is designed to handle both line-delimited JSON and concatenated JSON streaming:

echo '
> {"message": "hello"}
> {"message": "world!"}
> ' | fx .message
hello
world!

echo '
> {"message": "hello"}
> {"message": "world!"}
> ' | fx .message
hello
world!

Interactive Mode ​

While in interactive mode, press ? to display a list of available shortcuts.

Search ​

Initiate a search by pressing / and entering a regex pattern. Navigate using n (next) and N (previous).

Text Selection ​

Text selection in fx differs due to mouse event redirection to stdin. Depending on your terminal, use specific key combinations to select text: