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.
Please note that 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 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.
Derived from
Include files
<wx/process.h>
See also
Members
wxProcess::wxProcess
wxProcess::~wxProcess
wxProcess::CloseOutput
wxProcess::Detach
wxProcess::GetErrorStream
wxProcess::GetInputStream
wxProcess::GetOutputStream
wxProcess::IsErrorAvailable
wxProcess::IsInputAvailable
wxProcess::IsInputOpened
wxProcess::Kill
wxProcess::Exists
wxProcess::OnTerminate
wxProcess::Open
wxProcess::GetPid
wxProcess::Redirect
wxProcess(wxEvtHandler * parent = NULL, int id = -1)
wxProcess(int flags)
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.
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 wxPROCESS_DEFAULT or wxPROCESS_REDIRECT. Specifying the former value has no particular effect while using the latter one is equivalent to calling Redirect.
Parameters
parent
id
flags
~wxProcess()
Destroys the wxProcess object.
void 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 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.
wxInputStream* GetErrorStream() const
Returns an input stream which corresponds to the standard error output (stderr) of the child process.
wxInputStream* 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 wxProcess::Redirect.
wxOutputStream* 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 wxProcess::Redirect.
bool IsErrorAvailable() const
Returns true if there is data to be read on the child process standard error stream.
See also
bool 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
bool IsInputOpened() const
Returns true if the child process standard output stream is opened.
static wxKillError Kill(int pid, wxSignal signal = wxSIGNONE, int flags = wxKILL_NOCHILDREN)
Send the specified signal to the given process. Possible signal values are:
enum wxSignal
{
wxSIGNONE = 0, // verify if the process exists under Unix
wxSIGHUP,
wxSIGINT,
wxSIGQUIT,
wxSIGILL,
wxSIGTRAP,
wxSIGABRT,
wxSIGEMT,
wxSIGFPE,
wxSIGKILL, // forcefully kill, dangerous!
wxSIGBUS,
wxSIGSEGV,
wxSIGSYS,
wxSIGPIPE,
wxSIGALRM,
wxSIGTERM // terminate the process gently
};
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:
enum wxKillError
{
wxKILL_OK, // no error
wxKILL_BAD_SIGNAL, // no such signal
wxKILL_ACCESS_DENIED, // permission denied
wxKILL_NO_PROCESS, // no such process
wxKILL_ERROR // another, unspecified error
};
See alsowxProcess::Exists, wxKill, Exec sample
static bool Exists(int pid)
Returns true if the given process exists in the system.
See also
void OnTerminate(int pid, int status)
It is called when the process with the pid pid finishes. It raises a wxWidgets event when it isn't overridden.
pid
status
static wxProcess * Open(const wxString& cmd, int flags = wxEXEC_ASYNC)
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. 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
Return value
A pointer to new wxProcess object or NULL on error.
See also
long GetPid() const
Returns the process ID of the process launched by Open.
void 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.