esc-get-cmd-data-passthru-async

Run any shell command, get promise resolving/rejecting (or only resolving) with

• Return code
• Arrays of stdout/stderr

Optional

• Line filtering - positive/negative - using a [ function / string / regex ]
• Data-extraction/transformation - using a [ function / regex ]
• Pass-thru stdout/stderr (user can see cmd progress live)
• Error handling, however you want

My other NPM modules for running commands

Interactive (run and use nano/vim/installers/htop etc)

esc-get-interactive-cmd-result-async

Capture stdout or get custom arrays on error afterwards

esc-get-cmd-stdout-array-promise

Install

npm install esc-get-cmd-data-passthru-async

Usage

Run a command and get its output as arrays. Includes powerful options for filtering, mapping, and environment control.

Silly examples with familiar commands

List files, filter, and capture output:

import { getCmdDataP } from 'esc-get-cmd-data-passthru-async';

(async () => {
  try {
    const [ retCode, outA, errA ] = await getCmdDataP(
      'ls',
      ['-la'],
      {
        cwd: '/tmp/foo',
        passthru: true,                            // Print output live (default: true)
        filterOnly: line => line.endsWith('.txt'), // Only .txt files
        capture: line => line.toUpperCase(),       // Convert to uppercase
        env: { DEBUG: '1' },
        verbosity: 3,                              // Verbose logs (default: 3)
      }
    );
    console.log('retCode:', retCode);
    console.log('Stdout array:', outA);
    console.log('Stderr array:', errA);
  } catch ([ retCode, outA, errA ]) {
    console.error('retCode', retCode);
    console.log('Stdout array:', outA);
    console.log('Stderr array:', errA);
  }
})();

Silly one line examples

const [ retCode, outA, errA ] = await getCmdDataP('apt', ['update'], { capture:/https?:\/\/[^ ]+/ }); // get only the apt URL's

const [ retCode, outA, errA ] = await getCmdDataP('apt', ['update'], { filterOnly:'Hit', filterNot:'debian.org/' }); // Only get the lines containing Hit, but not the debian.org related lines.

const [ retCode, outA, errA ] = await getCmdDataP('apt', ['update'], { filterOnly:/(E|Err):/ }); // get only the apt URL's

const [ retCode, outA, errA ] = await getCmdDataP('df', ['-h'], { filterOnly:/(^Filesystem | \/$)/ }); // Get the headings and only the root filesystem's stats

const [ retCode, outA, errA ] = await getCmdDataP('zfs', ['list','yourmom'], { filterNot:/^NAME / });

Ping foo-pc with an interval of 0.5 seconds, timeout of 2 sec per ping, max 5 attempts, stop immediately when you get a reply, capture/return the milliseconds.

    const [ retCode, outA, errA ] = await getCmdDataP('ping', ['-i', '0.5', '-W', '2', '-c', '5', 'foo-pc'], { capture:/bytes from.+time=([\d.]+)/, until:'bytes from' });

API

getCmdDataP(cmd, argsA=[], optionsO={})

• cmd: String – Command to run.
• argsA: Array<string> – Command arguments.
• optionsO: Object
  • passthru: Boolean (default: true) – Print stdout/stderr to terminal live.
  • filterOnly: Function/RegExp/String – Include only lines matching this.
  • filterNot: Function/RegExp/String – Exclude lines matching this.
  • capture: Function/RegExp – Map/transforms each line before collecting.
  • until: Function/RegExp/String – Stop (kill process) once a match is seen:
    • Function: receives all new output lines, stop if returns truthy
    • String: stop if any new line includes it
    • RegExp: stop if any new line matches
  • verbosity: 0-3 (default:3) – Control log output:
    • 0:silent, 1:errors, 2:show commands, 3:show success
  • env: Object – Extra environment variables (merged with process.env).
  • spawnO: Object – Additional options for child_process.spawn.
  • rejectOnError: Boolean (default:true) – Rejects promise on error/exit code != 0. If false, always resolves.

Capture groups in capture regex

• If you have no capture groups, you get the whole match.
• If you have 1 capture group, you get what you captured.
• If you have 2+ capture groups, you get an array of your captures

Your capture groups should (not)? be optional. If you make them optional you will have to deal with a varying output format caused by your 🐂💩 regex.

Returns

A Promise resolving to:

[ exitCode, outA, errA ]

• exitCode: 0 on success; else reject with code > 0
• outA: Array of (possibly filtered/transformed) stdout lines
• errA: Array of (possibly filtered/transformed) stderr lines

Features

• No dependencies: Simple, fast, no bloat.
• Small: Only 6k of code
• Stable API: No breaking changes will ever be made.
• Passthrough: See output live by default, or disable for silent/asynchronous capture.
• Filtering/Mapping: Pick or modify output lines with strings, RegExp, or functions.
• Great for automation: User can watch progress, calling script gets all of the data output.
• No noise: Get only the data that you need
• Flexible Environment: Pass custom env variables, cwd, etc.
• Powerful: Get shit done!

Typical Scenarios

• Running build scripts, CLI tools, or diagnostics within Node.js
• Filtering logs, capturing only what you want from output
• Replacing heavy solutions like zx with something lighter, safer, and more transparent

License

MIT

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Say thanks by starring: esc-get-cmd-data-passthru-async on GitHub
Issues & PRs welcome!

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