Easily create a streaming pipeline of child processes using a tagged template literal, and mixin string processing in Javascript.

Full example:

const pipe = require('pipe-tag');

const psOptions = '--format cmd'

pipe`
    ps ${psOptions} |
    ${ line => line.toUpperCase() } |
    ${ pipe`sort` }
`.stdout.pipe(process.stdout);

Usage

A simple template string tagged with pipe spawns a child process and returns it's ChildProcess object.

pipe`ps`.stdout.pipe(process.stdout);

For convenience the passing the returned object to await buffers an array of Strings from it's stdout.

const processes = await pipe`ps`;

Function Placeholders

Placeholder expressions that produce Functions are executed once for each line output by the preceding child process, and then the results are sent to the stdin of the next step of the pipeline.

pipe`ps | ${ line => line.toUpperCase() }`.stdout.pipe(process.stdout);

Child Process Placeholders

Placeholder expressions that produce instances of ChildProcess (or similar) are added to the pipeline. The stdout of the preceding child process is piped to their stdin, and their stdout is piped to the stdin of the next step of the pipeline.

pipe`ps | ${ child_process.spawn('sort') }`.stdout.pipe(process.stdout);

The pipe template tag itself returns a ChildProcess object, so pipe template literals can be composed.

pipe`ps | ${ pipe`sort` }`.stdout.pipe(process.stdout);

Other Placeholders

All other placeholders are stringified and appended to the child process command (just like "normal" un-tagged template literals).

const psOptions = '--format cmd';
pipe`ps ${ psOptions }`.stdout.pipe(process.stdout);