dupsh

pipe together two shell commands full duplex

Given two shell commands a and b, pipe the output of a to the input of b and the output of b to the input of a:

a.stdout.pipe(b.stdin);
b.stdout.pipe(a.stdin);

This is a TypeScript version of the classic dupsh module.

• Install
• CLI
  • Use
• Library API
• Programmatic example

Install

npm i -S @substrate-system/dupsh

CLI

dupsh "CMD1" "CMD2"

Use

usage: dupsh {OPTIONS} CMD1 CMD2

  Spawn CMD1 and CMD2, piping the stdout of CMD1 to the stdin of CMD2,
  and the stdout of CMD2 to the stdin of CMD1.

  stderr from both processes is forwarded to the dupsh stderr.

OPTIONS are:

  -h --help  Show this message.

Library API

import { dupsh, exec } from 'dupsh'

type DupshCommand = string|readonly string[]

interface DupshOptions {
  spawn?:SpawnOptionsWithoutStdio
  stderr?:Writable
}

interface DupshResult {
  left:ChildProcessWithoutNullStreams
  right:ChildProcessWithoutNullStreams
  completion:Promise<number>
}

• dupsh(leftCommand, rightCommand, options) starts both commands and returns process handles plus a completion promise.
• exec(leftCommand, rightCommand, options) is a convenience wrapper that resolves to the final exit code.
• String commands run via shell (shell: true) to preserve CLI-style command usage.
• Array commands run directly without a shell ([file, ...args]).

Programmatic example

import { exec } from 'dupsh'

const code = await exec(
  [process.execPath, '-e', "process.stdout.write('A\\n')"],
  [process.execPath, '-e', "process.stdout.write('B\\n')"]
)

process.exitCode = code