exec

Call a child process with the ease of exec and safety of spawn

npm install exec
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exec

Call a child process with the ease of exec and safety of spawn

Note: The API has changed slightly with v0.1.0 of this module

UPDATE: If your version of node supports child_process.execFile, consider using that instead, as that does everything this module does and more... the usage is slightly different.

[http://nodejs.org/api/child_process.html#child_process_child_process_execfile_file_args_options_callback] (http://nodejs.org/api/child_process.html#child_process_child_process_execfile_file_args_options_callback)

Why?

This module provides the best of both worlds of spawn and exec

It will callback with 2 strings containing stdout and stderr (like child_process.exec), but will take an array of process arguments (like child_process.spawn) to avoid any potentially harmful shell expansion.

Usage

var exec = require('exec');

Example

var exec = require('exec');

exec(['ls', '-lha'], function(err, out, code) {
  if (err instanceof Error)
    throw err;
  process.stderr.write(err);
  process.stdout.write(out);
  process.exit(code);
});

The example above will call ls -lha safely, by passing the arguments directly to exec(2) without using an shell expansion/word splitting.

It returns a child_process.spawn object, and callbacks with any stdout, stderr, and the exit status of the command. The above example will throw an error if anything went wrong during the spawn, otherwise it will print the stdout, stderr, and exit with the exit code of ls.

NOTE: If err is an instanceof Error, it means that child_process.spawn emitted and error event, and err is set to that error object.

err and out are encoded asutf-8 strings by default

For backwards compatibility with child_process.exec, it is also possible to pass a string to exec. The string will automatically be converted to ['/bin/sh', '-c', '{string}'], which will cause the string to be parsed on the shell. Note that if you use this method, you are at risk of shell expansion, word splitting, and other shell features that could be potentially unsafe.

exec('cat foo | grep bar', function(err, out, code) {
  if (err instanceof Error)
    throw err;
  process.stderr.write(err);
  process.stdout.write(out);
  process.exit(code);
});

Functions

exec(['args'], [opts], callback)

  • args: an array of arguments to execute
  • opts: is additional options to pass to child_process.spawn

In addition to the child_process.spawn options, more options have been added to mimic the behavior of child_process.exec

  • opts.timeout: number of milliseconds to wait for the program to complete before sending it SIGTERM. Note that by default, your program will wait indefinitely for the spawned program to terminate. Upon sending the fatal signal, exec will return with whatever stdout and stderr was produced.
  • opts.killSignal: the signal to use when opts.timeout is used, defaults to SIGTERM
  • opts.encoding: the encoding to use for stdout and stderr. NOTE: unlike child_process.exec, this defaults to 'utf-8' if unset. Set to 'buffer' to handle binary data.

Installation

npm install exec

License

MIT

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