wxProcess Class Reference
[Application and Process Management]

#include <wx/process.h>

Inheritance diagram for wxProcess:

List of all members.

---

Detailed Description

The objects of this class are used in conjunction with the wxExecute() function. When a wxProcess object is passed to wxExecute(), 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 wxExecute() in the case of asynchronous execution.

Note:

If the process termination notification is processed by the parent, it is responsible for deleting the wxProcess 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 wxProcess::Detach for others).

wxProcess also supports IO redirection of the child process. For this, you have to call its Redirect() method before passing it to wxExecute(). 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.

Library:  wxBase

Category:  Application and Process Management

See also:

wxExecute(), exec sample

Public Member Functions
	wxProcess (wxEvtHandler *parent=NULL, int id=-1)
	wxProcess (int flags)
virtual	~wxProcess ()
void	CloseOutput ()
void	Detach ()
wxInputStream *	GetErrorStream () const
wxInputStream *	GetInputStream () const
wxOutputStream *	GetOutputStream () const
long	GetPid () const
bool	IsErrorAvailable () const
bool	IsInputAvailable () const
bool	IsInputOpened () const
virtual void	OnTerminate (int pid, int status)
void	Redirect ()
Static Public Member Functions
static bool	Exists (int pid)
static wxKillError	Kill (int pid, wxSignal signal=wxSIGNONE, int flags=wxKILL_NOCHILDREN)
static wxProcess *	Open (const wxString &cmd, int flags=wxEXEC_ASYNC)

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Constructor & Destructor Documentation

wxProcess::wxProcess	(	wxEvtHandler *	parent = NULL,
		int	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 NULL, 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	The event handler parent.
	id	id of an event.

wxProcess::wxProcess

(

int

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 wxPROCESS_DEFAULT or wxPROCESS_REDIRECT.

Specifying the former value has no particular effect while using the latter one is equivalent to calling Redirect().

virtual wxProcess::~wxProcess

(

)

[virtual]

Destroys the wxProcess object.

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Member Function Documentation

void wxProcess::CloseOutput

(

)

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.

void wxProcess::Detach

(

)

Normally, a wxProcess 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 wxProcess object, but should call Detach() instead. After the wxProcess 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 bool wxProcess::Exists

(

int

pid

)

[static]

Returns true if the given process exists in the system.

See also:

Kill(), Exec sample

wxInputStream* wxProcess::GetErrorStream

(

)

const

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

wxInputStream* wxProcess::GetInputStream

(

)

const

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 also:

Redirect().

wxOutputStream* wxProcess::GetOutputStream

(

)

const

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 also:

Redirect().

long wxProcess::GetPid

(

)

const

Returns the process ID of the process launched by Open().

bool wxProcess::IsErrorAvailable

(

)

const

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

See also:

IsInputAvailable()

bool wxProcess::IsInputAvailable

(

)

const

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 exec sample for an example of using this function.

See also:

IsInputOpened()

bool wxProcess::IsInputOpened

(

)

const

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

static wxKillError wxProcess::Kill	(	int	pid,
		wxSignal	signal = wxSIGNONE,
		int	flags = wxKILL_NOCHILDREN
	)			[static]

Send the specified signal to the given process. Possible signal values can be one of the wxSignal enumeration values.

wxSIGNONE, wxSIGKILL and wxSIGTERM have the same meaning under both Unix and Windows but all the other signals are equivalent to wxSIGTERM under Windows.

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

Returns the element of wxKillError enum.

See also:

Exists(), wxKill(), Exec sample

virtual void wxProcess::OnTerminate	(	int	pid,
		int	status
	)			[virtual]

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

Parameters:

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

static wxProcess* wxProcess::Open	(	const wxString &	cmd,
		int	flags = wxEXEC_ASYNC
	)			[static]

This static method replaces the standard popen() function: it launches the process specified by the cmd parameter and returns the wxProcess 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.

Remarks:

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 wxExecute(). Note: wxEXEC_SYNC should not be used.

Returns:

A pointer to new wxProcess object or NULL on error.

See also:

wxExecute()

void wxProcess::Redirect

(

)

Turns on redirection.

wxExecute() 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.