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# Wx::Process

The objects of this class are used in conjunction with the
Execute function. When a Process object is passed to
Execute(), its on_terminate virtual method
is called when the process terminates. This allows the program to be
(asynchronously) notified about the process termination and also retrieve its
exit status which is unavailable from Execute() in the case of
asynchronous execution.

Please note that if the process termination notification is processed by the
parent, it is responsible for deleting the Process object which sent it.
However, if it is not processed, the object will delete itself and so the
library users should only delete those objects whose notifications have been
processed (and call Detach for others).

Process also supports IO redirection of the child process. For this, you have
to call its Redirect method before passing it to
Execute. If the child process was launched successfully,
get_input_stream,
get_output_stream and
get_error_stream can then be used to retrieve
the streams corresponding to the child process standard output, input and
error output respectively.

## Derived from

EvtHandler

## See also

Execute

exec sample

## Methods

- Process.new
- Process#close_output
- Process#detach
- Process#get_error_stream
- Process#get_input_stream
- Process#get_output_stream
- Process#is_error_available
- Process#is_input_available
- Process#is_input_opened
- Process#kill
- Process#exists
- Process#on_terminate
- Process#open
- Process#redirect

### Process.new

Process.new(%(arg-type)EvtHandler% parent = nil, Integer id = -1) Process.new(%(arg-type)Integer% flags)

Constructs a process object. id is only used in the case you want to
use Widgets events. It identifies this object, or another window that will
receive the event.

If the parent parameter is different from NULL, it will receive
a EVT_END_PROCESS notification event (you should insert EVT_END_PROCESS
macro in the event table of the parent to handle it) with the given id.

The second constructor creates an object without any associated parent (and
hence no id neither) but allows to specify the flags which can have the
value of `PROCESS_DEFAULT` or `PROCESS_REDIRECT`. Specifying the
former value has no particular effect while using the latter one is equivalent
to calling Redirect.

#### Parameters

- parent The event handler parent.
- id id of an event.
- flags either `PROCESS_DEFAULT` or `PROCESS_REDIRECT`

destructor()

Destroys the Process object.

### Process#close_output

close_output()

Closes the output stream (the one connected to the stdin of the child
process). This function can be used to indicate to the child process that
there is no more data to be read – usually, a filter program will only
terminate when the input stream is closed.

### Process#detach

detach()

Normally, a Process object is deleted by its parent when it receives the
notification about the process termination. However, it might happen that the
parent object is destroyed before the external process is terminated (e.g. a
window from which this external process was launched is closed by the user)
and in this case it should not delete the Process object, but
should call Detach() instead. After the Process object is detached
from its parent, no notification events will be sent to the parent and the
object will delete itself upon reception of the process termination
notification.

### Process#get_error_stream

“InputStream* ":inputstream* .html get_error_stream()

Returns an input stream which corresponds to the standard error output (stderr)
of the child process.

### Process#get_input_stream

“InputStream* ":inputstream* .html get_input_stream()

It returns an input stream corresponding to the standard output stream of the
subprocess. If it is NULL, you have not turned on the redirection.
See Process#redirect.

### Process#get_output_stream

“OutputStream* ":outputstream* .html get_output_stream()

It returns an output stream correspoding to the input stream of the subprocess.
If it is NULL, you have not turned on the redirection.
See Process#redirect.

### Process#is_error_available

Boolean is_error_available()

Returns `true` if there is data to be read on the child process standard
error stream.

#### See also

is_input_available

### Process#is_input_available

Boolean is_input_available()

Returns `true` if there is data to be read on the child process standard
output stream. This allows to write simple (and extremely inefficient)
polling-based code waiting for a better mechanism in future Widgets versions.

See the exec sample for an example of using this
function.

#### See also

is_input_opened

### Process#is_input_opened

Boolean is_input_opened()

Returns `true` if the child process standard output stream is opened.

### Process#kill

KillError kill(%(arg-type)Integer% pid, Signal signal = SIGNONE, Integer flags = KILL_NOCHILDREN)

Send the specified signal to the given process. Possible signal values are:

enum Signal { SIGNONE = 0, // verify if the process exists under Unix SIGHUP, SIGINT, SIGQUIT, SIGILL, SIGTRAP, SIGABRT, SIGEMT, SIGFPE, SIGKILL, // forcefully kill, dangerous! SIGBUS, SIGSEGV, SIGSYS, SIGPIPE, SIGALRM, SIGTERM // terminate the process gently };

`SIGNONE`, `SIGKILL` and `SIGTERM` have the same meaning
under both Unix and Windows but all the other signals are equivalent to
`SIGTERM` under Windows.

The flags parameter can be KILL_NOCHILDREN (the default),
or KILL_CHILDREN, in which case the child processes of this
process will be killed too. Note that under Unix, for KILL_CHILDREN
to work you should have created the process passing EXEC_MAKE_GROUP_LEADER.

Returns the element of `KillError` enum:

enum KillError { KILL_OK, // no error KILL_BAD_SIGNAL, // no such signal KILL_ACCESS_DENIED, // permission denied KILL_NO_PROCESS, // no such process KILL_ERROR // another, unspecified error };

#### See also

Process#exists, Kill, Exec sample

### Process#exists

Boolean exists(%(arg-type)Integer% pid)

Returns `true` if the given process exists in the system.

#### See also

Process#kill, Exec sample

### Process#on_terminate

on_terminate(%(arg-type)Integer% pid, Integer status)

It is called when the process with the pid pid finishes.
It raises a Widgets event when it isn’t overridden.

- pid The pid of the process which has just terminated.
- status The exit code of the process.

### Process#open

Process open(%(arg-type)String% cmd, Integer flags = EXEC_ASYNC)

This static method replaces the standard `popen()` function: it launches
the process specified by the cmd parameter and returns the Process
object which can be used to retrieve the streams connected to the standard
input, output and error output of the child process.

If the process couldn’t be launched, `NULL` is returned. Note that in any
case the returned pointer should not be deleted, rather the process
object will be destroyed automatically when the child process terminates. This
does mean that the child process should be told to quit before the main program
exits to avoid memory leaks.

#### Parameters

- cmd The command to execute, including optional arguments.
- flags The flags to pass to Execute.
  NOTE: EXEC_SYNC should not be used.

#### Return value

A pointer to new Process object or `NULL` on error.

#### See also

Execute

### Process#redirect

redirect()

Turns on redirection. Execute will try to open a couple of pipes
to catch the subprocess stdio. The caught input stream is returned by
GetOutputStream() as a non-seekable stream. The caught output stream is returned
by GetInputStream() as a non-seekable stream.

[This page automatically generated from the Textile source at 2023-06-09 00:45:29 +0000]