If it is NULL, you have not turned on the redirection.
See \helpref{wxProcess::Redirect}{wxprocessredirect}.
+\membersection{wxProcess::Kill}\label{wxprocesskill}
+
+\func{static wxKillError}{Kill}{\param{int}{ pid}, \param{wxSignal}{ signal = wxSIGNONE}}
+
+Send the specified signal to the given process. Possible signal values are:
+
+\begin{verbatim}
+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
+};
+\end{verbatim}
+
+{\tt wxSIGNONE}, {\tt wxSIGKILL} and {\tt wxSIGTERM} have the same meaning
+under both Unix and Windows but all the other signals are equivalent to
+{\tt wxSIGTERM} under Windows.
+
+Returns the element of {\tt wxKillError} enum:
+
+\begin{verbatim}
+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
+};
+\end{verbatim}
+
+\wxheading{See also}
+
+\helpref{wxProcess::Exists}{wxprocessexists},\rtfsp
+\helpref{wxKill}{wxkill},\rtfsp
+\helpref{Exec sample}{sampleexec}
+
+\membersection{wxProcess::Kill}\label{wxprocessexists}
+
+\func{static bool}{Exists}{\param{int}{ pid}}
+
+Returns {\tt TRUE} if the given process exists in the system.
+
+\wxheading{See also}
+
+\helpref{wxProcess::Kill}{wxprocesskill},\rtfsp
+\helpref{Exec sample}{sampleexec}
+
\membersection{wxProcess::OnTerminate}\label{wxprocessonterminate}
\constfunc{void}{OnTerminate}{\param{int}{ pid}, \param{int}{ status}}