Using nodejs's spawn causes “unknown option — ” and “[Error: spawn ENOENT]” errors

问题

I'm trying to get spawn to effect an rm -rf node_modules followed by npm install (on windows 7; nx commands courtesy of a transparently installed CygWin. All nx commands resolve on a commandline just fine).

I initially had this using exec, but wanted to catch the stdout/stderr information as it occurred, so I figured I'd use spawn, and rewrote the code to use that. However, that breaks everything.

The rm command, rewritten, became this:

var spawn = require("child_process").spawn,
    child = spawn("rm", ["-rf", "node_modules"]);
child.stdout.on('data', function (data) { console.log(data.toString()); });
child.stderr.on('data', function (data) { console.log(data.toString()); });
child.on('error', function() { console.log(arguments); });

However, running this generates the following error:

rm: unknown option -- ,

Try `rm --help' for more information.

The npm command, rewritten, became this:

var spawn = require("child_process").spawn,
    child = spawn("npm", ["install"]);
child.stdout.on('data', function (data) { console.log(data.toString()); });
child.stderr.on('data', function (data) { console.log(data.toString()); });
child.on('error', function() { console.log(arguments); });

However, running this generates the following error:

{
  '0': {
    [Error: spawn ENOENT]
    code: 'ENOENT',
    errno: 'ENOENT',
    syscall: 'spawn'
  }
}

How do I make spawn run the same commands that worked fine using exec without it throwing up errors all over the place? And why does this not work? Reading the API, http://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options, seems to suggest this is precisely how one is supposed to use spawn...

回答1:

After lots of trying different things, I finally had a look at what "npm" actually is on windows, and it turns out to be a bash script called npm, as well as a windows-native batch script called npm.cmd (no idea why it's .cmd, that should be .bat, but there you have it). Windows's command resolver will see npm, notice that it's not an executable, see npm.cmd, and then notice that IS an executable, and will then use that instead. This is helpful when you're in a terminal, but spawn() will not do any such resolution: passing it npm will make it fail because it's not an executable. Passing it npm.cmd as command, however, works just fine.

(Also, not sure why rm was failing earlier, since that actually works correctly without any changes that I can tell. Probably misread that as part of the problem when in fact it wasn't.)

So: if you run into spawn saying ENOENT in windows, when the command you're trying to trigger works in a plain command prompt, find out if the command you're calling is a true executable, or whether there's a .bat/.cmd file that the command prompt will "helpfully" run for you instead. If so, spawn that.

edit

since this post is still getting upvotes, a good way to ensure the command always works is to bootstrap it based on process.platform, which will be win32 for windows.

var npm = (process.platform === "win32" ? "npm.cmd" : "npm"),
    child = spawn(npm, ["install", ...]);
...

回答2:

I think this may be some sort of cygwin gotcha. I'm running Ubuntu 12.04 and tried to duplicate your problem, but it works just fine for me. In short, I don't see anything you are doing wrong.

If it is complaining about the option, maybe split it up into multiple options like so:

child = spawn("rm", ["-r", "-f", "node_modules"]);

That's kind of a hail mary, but that works on my Ubuntu 12.04 as well. You might try to just delete a single file and see if you get the same thing.

child = spawn("rm", ["/home/username/Desktop/TestFile"]);

If that still fails, then you know you are working against some crazy stuff.

You could even try to just execute a command with no parameters like so:

child = spawn("ls");

If that still fails, you aren't likely to get spawn to work at all would be my guess and be grateful that at least exec is working.

Not much in the realm of answers for you, but like I said, I can't see anything you are doing incorrectly.

Furthermore, I don't see how your npm command is going to work because you aren't specifying what to install, but that being said, it fails in a different way than I'm seeing it fail here if I use the same command. . . I see lots of stderr output, not an overall error.

BTW, I'm running node v0.8.21. You can query that by node -v. If you are running another version, maybe give 0.8.21 a try.

回答3:

Use full path for the process, like:

var cmd = require('child_process').spawn("C:\\windows\\system32\\cmd.exe");

来源：https://stackoverflow.com/questions/17516772/using-nodejss-spawn-causes-unknown-option-and-error-spawn-enoent-err

标签

node.js

exec

spawn