Execute cygwin command from NodeJS

Question

Using Node's child_process module, I'd like to execute commands via the cygwin shell. This is what I'm trying:

var exec = require('child_process').execSync;
exec('mkdir -p a/b/c', {shell : 'c:/cygwin64/bin/bash.exe -c'});

TypeError: invalid data
    at WriteStream.Socket.write (net.js:641:11)
    at execSync (child_process.js:503:20)
    at repl:1:1
    at REPLServer.defaultEval (repl.js:262:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer. (repl.js:431:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:212:10)

I can see Node's child_process.js will add the /s and /c switches , regardless of the shell option being set, bash.exe doesn't know what to do with these arguments.

I found a work around for this problem but it's really not ideal:

exec('c:/cygwin64/bin/bash.exe -c "mkdir -p a/b/c"');

Doing the above would obviously only work on Windows not unix systems.

How can I execute commands in the cygwin shell from NodeJS?

Answer 1

This is not a complete generic solution, because more would need to be done with some of the options of exec() , but this should allow you to write code that will work on unixes, Windows and cygwin, differentiating between the later two.

This solution assumes that Cygwin is installed in a directory which name includes the string cygwin .

var child_process = require( 'child_process' )
  , home = process.env.HOME
;

function exec( command, options, next ) {
  if( /cygwin/.test( home ) ) {
    command = home.replace( /(cygwin[0-9]*).*/, "$1" ) + "\\bin\\bash.exe -c '" + command.replace( /\\/g, '/' ).replace( /'/g, "\'" ) + "'";
  }

  child_process.exec( command, options, next );
}

You could alternatively hijack child_process.exec conditionally when running under Cygwin:

var child_process = require( 'child_process' )
  , home = process.env.HOME
;

if( /cygwin/.test( home ) ) {
  var child_process_exec = child_process.exec
    , bash = home.replace( /(cygwin[0-9]*).*/, "$1" ) + "\\bin\\bash.exe"
  ;

  child_process.exec = function( command, options, next ) {
    command = bash + " -c '" + command.replace( /\\/g, '/' ).replace( /'/g, "\'" ) + "'";

    child_process_exec( command, options, next )
  }
}