How to use the child_process.spawn.bind function in child_process

/* jshint node:true */
"use strict";

var spawn = require("child_process").spawn,
	ffmpeg = spawn.bind(null, process.env.FFMPEG_PATH || "ffmpeg"),
	fs = require("fs"),
	through = require("through"),
	concat = require("concat-stream");

module.exports.read = function(src, options, callback) {
	if (typeof options === "function") {
		callback = options;
		options = {};
	}

	var args = getReadArgs(src, options);

	if (options.dryRun) {
		return args;
	}

function command2function(cmd) {
	switch (typeof cmd) {
		case 'string':
			var args = cmd.split(' ');
			var command = args.shift();

			cmd = spawn.bind(undefined, command, args);
			break;
		case 'object':
			var command = cmd && cmd.command;
			if (command) {
				var args = cmd.args;
				var options = cmd.options;

				cmd = spawn.bind(undefined, command, args, options);
			}
			break;
	}

	return cmd
}

function command2function(cmd) {
	switch (typeof cmd) {
		case 'string':
			var args = cmd.split(' ');
			var command = args.shift();

			cmd = spawn.bind(undefined, command, args);
			break;
		case 'object':
			var command = cmd && cmd.command;
			if (command) {
				var args = cmd.args;
				var options = cmd.options;

				cmd = spawn.bind(undefined, command, args, options);
			}
			break;
	}

	return cmd
}

function command2function(cmd)
{
  switch(typeof cmd)
  {
    case 'string':
    {
      var args = cmd.split(' ');
      var command = args.shift();

      cmd = spawn.bind(undefined, command, args);
    }
    break;

    case 'object':
    {
      var command = cmd && cmd.command;
      if(command)
      {
        var args = cmd.args;
        var options = cmd.options;

        cmd = spawn.bind(undefined, command, args, options);
      }
    }
    break;
  }

var args = cmd.split(' ');
      var command = args.shift();

      cmd = spawn.bind(undefined, command, args);
    }
    break;

    case 'object':
    {
      var command = cmd && cmd.command;
      if(command)
      {
        var args = cmd.args;
        var options = cmd.options;

        cmd = spawn.bind(undefined, command, args, options);
      }
    }
    break;
  }

  return cmd
}