Redirect between stderr and stdout in `Deno.Command`

[nayeemrmn]

Ref https://github.com/denoland/deno/pull/1828#issuecomment-467719574

Rather than adding Process::combinedOutput(), I propose modelling 2>&1 in RunOptions.

Ref https://docs.python.org/3/library/subprocess.html#using-the-subprocess-module

export interface RunOptions {
  cmd: string[];
  cwd?: string;
  env?: {
    [key: string]: string;
  };
  stdout?: ProcessStdio | number;
  stderr?: ProcessStdio | number;
  stdin?: ProcessStdio | number;
}

->

export interface RunOptions {
  cmd: string[];
  cwd?: string;
  env?: {
    [key: string]: string;
  };
  stdout?: ProcessStdio | number;
  stderr?: ProcessStdio | "stdout" | number;
  stdin?: ProcessStdio | number;
}

[brandonkal]

This would be very convenient when a program outputs on stdout when it should be on Deno's stderr. This would be especially nice if it streamed.

Process::combinedOutput() may be nice as well but not as useful if the Promise only resolved when the process exits.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[jeff-hykin]

Thanks to some help from crowlKats in the discord, I created a Sprinter to make subprocesses more convenient. If people find it useful I'll upgrade it over time.

import { run, Out, Stdout, Stderr, Overwrite, AppendTo, Timeout } from "https://deno.land/x/sprinter@0.2.0/index.js"

// yes &> my_log.txt
await run("yes", Out(Overwrite("my_log.txt")))

// yes &>> my_log.txt
await run("yes", Out(AppendTo("my_log.txt")))

// yes 1>> my_log.txt
await run("yes", Stdout(AppendTo("my_log.txt")))

// yes 1>my_log.txt 2>>my_error_log.txt
await run("yes", Stdout(Overwrite("my_log.txt")), Stderr(AppendTo("my_error_log.txt")))

// using an already-open file
const file = await Deno.open("./my_log.txt", { read: false, write: true, create: true, })
await run("yes", Out(AppendTo(file)))

// with a timeout
await run("yes", Out(AppendTo(file)), Timeout({ gentlyBy: 100, waitBeforeUsingForce: 500}))

There's more, like piping multiple files as input and multiple files as output, but those above should cover the basic use-cases.