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ProcessEvent

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phoenix_title Process

The objects of this class are used in conjunction with the Execute function.

When a Process object is passed to Execute, its OnTerminate 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.

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, GetInputStream, GetOutputStream and GetErrorStream can then be used to retrieve the streams corresponding to the child process standard output, input and error output respectively.

events Events Emitted by this Class

Handlers bound for the following event types will receive a ProcessEvent parameter.

  • EVT_END_PROCESS: Process a wxEVT_END_PROCESS event, sent by Process.OnTerminate upon the external process termination.

Note

If the wxEVT_END_PROCESS event sent after termination is processed by the parent, then 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 Process.Detach for others). This also means that unless you’re going to process the wxEVT_END_PROCESS event, you must allocate the Process class on the heap.

See also

Execute,


class_hierarchy Inheritance Diagram

Inheritance diagram for class Process

Inheritance diagram of Process


method_summary Methods Summary

__init__ Constructs a process object.
CloseOutput Closes the output stream (the one connected to the stdin of the child process).
Detach Detaches this event handler from the parent specified in the constructor (see EvtHandler.Unlink for a similar but not identic function).
Exists Returns True if the given process exists in the system.
GetErrorStream Returns an input stream which corresponds to the standard error output (stderr) of the child process.
GetInputStream It returns an input stream corresponding to the standard output stream of the subprocess.
GetOutputStream It returns an output stream corresponding to the input stream of the subprocess.
GetPid Returns the process ID of the process launched by Open or set by Execute (if you passed this Process as argument).
IsErrorAvailable Returns True if there is data to be read on the child process standard error stream.
IsInputAvailable Returns True if there is data to be read on the child process standard output stream.
IsInputOpened Returns True if the child process standard output stream is opened.
Kill Send the specified signal to the given process.
OnTerminate It is called when the process with the pid pid finishes.
Open 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.
Redirect Turns on redirection.

api Class API


class Process(EvtHandler)

The objects of this class are used in conjunction with the Execute() function.

Possible constructors:

Process(parent=None, id=-1)

Process(flags)

Methods


__init__(self, *args, **kw)

overload Overloaded Implementations:


__init__ (self, parent=None, id=-1)

Constructs a process object.

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

If the parent parameter is different from None, it will receive a wxEVT_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.

Parameters:
  • parent (EvtHandler) – The event handler parent.
  • id (int) – id of an event.


__init__ (self, flags)

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:flags (int) –



CloseOutput(self)

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.

Notice that GetOutputStream will return None after the output stream is closed.


Detach(self)

Detaches this event handler from the parent specified in the constructor (see EvtHandler.Unlink for a similar but not identic function).

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.


static Exists(pid)

Returns True if the given process exists in the system.

Parameters:pid (int) –
Return type:bool

See also

Kill ,


GetErrorStream(self)

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

Return type: InputStream

GetInputStream(self)

It returns an input stream corresponding to the standard output stream of the subprocess.

If it is None, you have not turned on the redirection.

Return type: InputStream

See also

Redirect .


GetOutputStream(self)

It returns an output stream corresponding to the input stream of the subprocess.

If it is None, you have not turned on the redirection or already called CloseOutput .

Return type: OutputStream

See also

Redirect .


GetPid(self)

Returns the process ID of the process launched by Open or set by Execute (if you passed this Process as argument).

Return type:long

IsErrorAvailable(self)

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

Return type:bool

See also

IsInputAvailable


IsInputAvailable(self)

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 wxWidgets versions. See the for an example of using this function.

Return type:bool

See also

IsInputOpened


IsInputOpened(self)

Returns True if the child process standard output stream is opened.

Return type:bool

static Kill(pid, sig=SIGTERM, flags=KILL_NOCHILDREN)

Send the specified signal to the given process.

Possible signal values can be one of the Signal enumeration values.

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.

Parameters:
  • pid (int) –
  • sig (Signal) –
  • flags (int) –
Return type:

KillError

See also

Exists , Kill,


OnTerminate(self, pid, status)

It is called when the process with the pid pid finishes.

It raises a wxWidgets event when it isn’t overridden.

Note that this function won’t be called if you Kill the process.

Parameters:
  • pid (int) – The pid of the process which has just terminated.
  • status (int) – The exit code of the process.

static Open(cmd, 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, None is returned.

Parameters:
  • cmd (string) – The command to execute, including optional arguments.
  • flags (int) – The flags to pass to Execute. Note: EXEC_SYNC should not be used.
Return type:

Process
Returns:

A pointer to new Process object or None on error.

Note

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.

See also

Execute


Redirect(self)

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.


Properties


ErrorStream

See GetErrorStream


InputStream

See GetInputStream


OutputStream

See GetOutputStream


Pid

See GetPid

© Copyright 2012, Andrea Gavana. Created using Sphinx 1.2pre.