Functions
---------

#### `ps.spawn(command, [args], [options])`

For details about function arguments please refer to the api documentation of
[child_process.spawn(command, [args], [options])](http://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options)


#### `ps.exec(command, [options], callback)`

For details about function arguments please refer to the api documentation of
[child_process.exec(command, [options], callback)](http://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback)


#### `ps.execFile(file, [args], [options], [callback])`

For details about function arguments please refer to the api documentation of
[child_process.execFile(file, [args], [options], [callback])](http://nodejs.org/api/child_process.html#child_process_child_process_execfile_file_args_options_callback)

#### `ps.factory(useTmpIn, useTmpOut, callback)`

This function uses the provided callback to connect input and output of the resulting stream. `useTmpIn` and `useTmpOut` are booleans that define which
parts of the stream temp should use temp files.
`callback` has the signature `function(input, output, callback)`. "input" and "output" are either streams of paths of temporary files. The callback must
be called when data is available for output. If "tmpUseOut" is `false`, this can be called immediately. It "tmpUseOut" is `true` it must be called, when the
output tempfile has completely been written to.


Changing the placeholder tokens
-------------------------------
The tokens `<INPUT>` and `<OUTPUT>` can be changed:

{{example 'examples/placeholders.js'}}

Events
------
Process errors (such as not finding the executable file) are emitted on the resulting stream as `'error'` event.
The `'started'` event is emitted when the is started. Its first argument is the child-process object, second and
third arguments are the `command` and `args` passed to `ps.exec`, `ps.spawn` or `ps.execFile`), but with the
placeholders resolved to the their actual temporary files.

{{example 'examples/events.js'}}