node.js execute system command synchronously


Question

I need in node.js function

result = execSync('node -v');

that will synchronously execute the given command line and return all stdout'ed by that command text.

ps. Sync is wrong. I know. Just for personal use.

UPDATE

Now we have mgutz's solution which gives us exit code, but not stdout! Still waiting for a more precise answer.

UPDATE

mgutz updated his answer and the solution is here :)
Also, as dgo.a mentioned, there is stand-alone module exec-sync

UPDATE 2014-07-30

ShellJS lib arrived. Consider this is the best choice for now.


UPDATE 2015-02-10

AT LAST! NodeJS 0.12 supports execSync natively.
See official docs

1
161
6/29/2015 2:56:49 PM

Accepted Answer

Node.js (since version 0.12 - so for a while) supports execSync:

child_process.execSync(command[, options])

You can now directly do this:

const execSync = require('child_process').execSync;
code = execSync('node -v');

and it'll do what you expect. (Defaults to pipe the i/o results to the parent process). Note that you can also spawnSync now.

128
12/19/2017 8:47:44 PM

See execSync library.

It's fairly easy to do with node-ffi. I wouldn't recommend for server processes, but for general development utilities it gets things done. Install the library.

npm install node-ffi

Example script:

var FFI = require("node-ffi");
var libc = new FFI.Library(null, {
  "system": ["int32", ["string"]]
});

var run = libc.system;
run("echo $USER");

[EDIT Jun 2012: How to get STDOUT]

var lib = ffi.Library(null, {
    // FILE* popen(char* cmd, char* mode);
    popen: ['pointer', ['string', 'string']],

    // void pclose(FILE* fp);
    pclose: ['void', [ 'pointer']],

    // char* fgets(char* buff, int buff, in)
    fgets: ['string', ['string', 'int','pointer']]
});

function execSync(cmd) {
  var
    buffer = new Buffer(1024),
    result = "",
    fp = lib.popen(cmd, 'r');

  if (!fp) throw new Error('execSync error: '+cmd);

  while(lib.fgets(buffer, 1024, fp)) {
    result += buffer.readCString();
  };
  lib.pclose(fp);

  return result;
}

console.log(execSync('echo $HOME'));

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