nolu

nolu is a small command-line tool to write one-liners in JavaScript (Node.js).

$ cat test.txt
Lorem 100
Ipsum 42
DolorSitAmet 1
$ cat test.txt | nolu -an --BEGIN "total = 0" -e "total += Number($F[1])" --END "console.log(total)"
143

The Node.js binary node provides nothing for one-liners except -e <code> option which simply executes eval(code). Nolu extends this -e with Ruby compatible options such as -n (process each line), -a (auto-split mode) and more.

Install

You need to have Node.js. Install nolu globally with:

npm i -g nolu

Leave off -g if you don't want to install globally.

Usage

$ nolu [options]

The following options are available:

Option	Description
-a	Turns on auto-split mode when used with -n or -p. In auto-split mode, $F = $_.split(/\s/) at beginning of each loop.
-B <code>, --BEGIN <code>	Execute code before any -es.
-e <code>	Execute code. Multiple -e's are executed in given order.
-E <code>, --END <code>	Execute code after all -e's.
-f	Assume your code for -e is a function and call it with $_ and $F. When using with -p, print the return value instead of $_.
-F <pattern>	Use pattern (regexp) for split() in auto-split mode (-a).
-h, --help	Output the help.
-j	Read process.stdin as JSON and set it to $_ before execute -e.
-J	Apply JSON.stringify() for printing (-p).
-l	Enables automatic line-ending processing, which means to chops every "\n" at the end of line. Works with -n or -p.
-n	Read process.stdin and store it $_ and execute -e for each line.
-p	Same with -n but print $_ (or the returned value when -f) after each loop.
-t	Read process.stdin and set it to $_ before execute -e (after --BEGIN).
-v, --version	Output the version.

Examples

A Classical Text Operation: Calculate The Average

$ cat test.txt
Lorem 100
Ipsum 42
DolorSitAmet 1
$ cat test.txt | nolu -an --BEGIN 'total = 0, lines = 0' -e 'lines++; total += Number($F[1])' --END 'console.log(total/lines)'
47.666666666666664

Use --BEGIN and --END options (-B and -E for short, respectively) instead of BEGIN{...} and END{...} block in Ruby. Any variables are shared between all codes.

NOTE that you may have to use single quote (') to write codes to avoid expanding $_ as an environment variable by your shell.

Handling JSON

For simple JSON transformation, jq may be a good option. nolu provides another, more plain-JavaScript friendly way to write complex filter.

A simple example:

$ cat test.json
{
  "value": 42,
  "v2": 100,
  "foo": 20
}
$ cat test.json | nolu -jJpe '$_ = Object.keys($_).map(k => $_[k])'
[
  42,
  100,
  20
]

When -j option is specified, nolu reads stdin as JSON (and store it to $_). -J modifies -p to print JSON.stringify($_, null, 2).

More functional way

Instead of refering/assigning $_, you can use a function by -f options.

$ cat test.txt
Lorem
Ipsum
DolorSitAmet
$ cat test.txt | nolu -pfe 'line => line.toUpperCase()'
LOREM
IPSU
DOLORSITAMET

The return value of the funciton is used to print (-p).

Simple pipe

The -t option simply read the whole content of process.stdin and give it to $_.

$ cat test.txt
Lorem
Ipsum
DolorSitAmet
$ cat test.txt | nolu -te 'fs.writeFileSync("out.txt", $_.toLowerCase())'
$ cat out.txt
lorem
ipsum
dolorsitamet

Note that fs is the fs core module of Node.js. No fs = require("fs") is needed. Any code evaluated in nolu are able to refer the core modules with their names.

License

MIT. See LICENSE.