docs/latex/wx/process.tex

   1 \section{\class{wxProcess}}\label{wxprocess}
   2
   3 The objects of this class are used in conjunction with the
   4 \helpref{wxExecute}{wxexecute} function. When a wxProcess object is passed to
   5 wxExecute(), its \helpref{OnTerminate()}{wxprocessonterminate} virtual method
   6 is called when the process terminates. This allows the program to be
   7 (asynchronously) notified about the process termination and also retrieve its
   8 exit status which is unavailable from wxExecute() in the case of
   9 asynchronous execution.
  10
  11 Please note that if the process termination notification is processed by the
  12 parent, it is responsible for deleting the wxProcess object which sent it.
  13 However, if it is not processed, the object will delete itself and so the
  14 library users should only delete those objects whose notifications have been
  15 processed (and call \helpref{Detach()}{wxprocessdetach} for others).
  16
  17 wxProcess also supports IO redirection of the child process. For this, you have
  18 to call its \helpref{Redirect}{wxprocessredirect} method before passing it to
  19 \helpref{wxExecute}{wxexecute}. If the child process was launched successfully,
  20 \helpref{GetInputStream}{wxprocessgetinputstream},
  21 \helpref{GetOutputStream}{wxprocessgetoutputstream} and
  22 \helpref{GetErrorStream}{wxprocessgeterrorstream} can then be used to retrieve
  23 the streams corresponding to the child process standard output, input and
  24 error output respectively.
  25
  26 \perlnote{In wxPerl this class has an additional {\tt Destroy} method,
  27 for explicit destruction.}
  28
  29 \wxheading{Derived from}
  30
  31 \helpref{wxEvtHandler}{wxevthandler}
  32
  33 \wxheading{Include files}
  34
  35 <wx/process.h>
  36
  37 \wxheading{Library}
  38
  39 \helpref{wxBase}{librarieslist}
  40
  41 \wxheading{See also}
  42
  43 \helpref{wxExecute}{wxexecute}\\
  44 \helpref{exec sample}{sampleexec}
  45
  46 \latexignore{\rtfignore{\wxheading{Members}}}
  47
  48 \membersection{wxProcess::wxProcess}\label{wxprocessctor}
  49
  50 \func{}{wxProcess}{\param{wxEvtHandler *}{ parent = NULL}, \param{int}{ id = -1}}
  51
  52 \func{}{wxProcess}{\param{int }{flags}}
  53
  54 Constructs a process object. {\it id} is only used in the case you want to
  55 use wxWidgets events. It identifies this object, or another window that will
  56 receive the event.
  57
  58 If the {\it parent} parameter is different from NULL, it will receive
  59 a wxEVT\_END\_PROCESS notification event (you should insert EVT\_END\_PROCESS
  60 macro in the event table of the parent to handle it) with the given {\it id}.
  61
  62 The second constructor creates an object without any associated parent (and
  63 hence no id neither) but allows to specify the {\it flags} which can have the
  64 value of {\tt wxPROCESS\_DEFAULT} or {\tt wxPROCESS\_REDIRECT}. Specifying the
  65 former value has no particular effect while using the latter one is equivalent
  66 to calling \helpref{Redirect}{wxprocessredirect}.
  67
  68 \wxheading{Parameters}
  69
  70 \docparam{parent}{The event handler parent.}
  71
  72 \docparam{id}{id of an event.}
  73
  74 \docparam{flags}{either {\tt wxPROCESS\_DEFAULT} or {\tt wxPROCESS\_REDIRECT}}
  75
  76 \membersection{wxProcess::\destruct{wxProcess}}\label{wxprocessdtor}
  77
  78 \func{}{\destruct{wxProcess}}{\void}
  79
  80 Destroys the wxProcess object.
  81
  82 \membersection{wxProcess::CloseOutput}\label{wxprocesscloseoutput}
  83
  84 \func{void}{CloseOutput}{\void}
  85
  86 Closes the output stream (the one connected to the stdin of the child
  87 process). This function can be used to indicate to the child process that
  88 there is no more data to be read - usually, a filter program will only
  89 terminate when the input stream is closed.
  90
  91 \membersection{wxProcess::Detach}\label{wxprocessdetach}
  92
  93 \func{void}{Detach}{\void}
  94
  95 Normally, a wxProcess object is deleted by its parent when it receives the
  96 notification about the process termination. However, it might happen that the
  97 parent object is destroyed before the external process is terminated (e.g. a
  98 window from which this external process was launched is closed by the user)
  99 and in this case it {\bf should not delete} the wxProcess object, but
 100 {\bf should call Detach()} instead. After the wxProcess object is detached
 101 from its parent, no notification events will be sent to the parent and the
 102 object will delete itself upon reception of the process termination
 103 notification.
 104
 105 \membersection{wxProcess::GetErrorStream}\label{wxprocessgeterrorstream}
 106
 107 \constfunc{wxInputStream* }{GetErrorStream}{\void}
 108
 109 Returns an input stream which corresponds to the standard error output (stderr)
 110 of the child process.
 111
 112 \membersection{wxProcess::GetInputStream}\label{wxprocessgetinputstream}
 113
 114 \constfunc{wxInputStream* }{GetInputStream}{\void}
 115
 116 It returns an input stream corresponding to the standard output stream of the
 117 subprocess. If it is NULL, you have not turned on the redirection.
 118 See \helpref{wxProcess::Redirect}{wxprocessredirect}.
 119
 120 \membersection{wxProcess::GetOutputStream}\label{wxprocessgetoutputstream}
 121
 122 \constfunc{wxOutputStream* }{GetOutputStream}{\void}
 123
 124 It returns an output stream correspoding to the input stream of the subprocess.
 125 If it is NULL, you have not turned on the redirection.
 126 See \helpref{wxProcess::Redirect}{wxprocessredirect}.
 127
 128 \membersection{wxProcess::IsErrorAvailable}\label{wxprocessiserroravailable}
 129
 130 \constfunc{bool}{IsErrorAvailable}{\void}
 131
 132 Returns {\tt true} if there is data to be read on the child process standard
 133 error stream.
 134
 135 \wxheading{See also}
 136
 137 \helpref{IsInputAvailable}{wxprocessisinputavailable}
 138
 139 \membersection{wxProcess::IsInputAvailable}\label{wxprocessisinputavailable}
 140
 141 \constfunc{bool}{IsInputAvailable}{\void}
 142
 143 Returns {\tt true} if there is data to be read on the child process standard
 144 output stream. This allows to write simple (and extremely inefficient)
 145 polling-based code waiting for a better mechanism in future wxWidgets versions.
 146
 147 See the \helpref{exec sample}{sampleexec} for an example of using this
 148 function.
 149
 150 \wxheading{See also}
 151
 152 \helpref{IsInputOpened}{wxprocessisinputopened}
 153
 154 \membersection{wxProcess::IsInputOpened}\label{wxprocessisinputopened}
 155
 156 \constfunc{bool}{IsInputOpened}{\void}
 157
 158 Returns {\tt true} if the child process standard output stream is opened.
 159
 160 \membersection{wxProcess::Kill}\label{wxprocesskill}
 161
 162 \func{static wxKillError}{Kill}{\param{int}{ pid}, \param{wxSignal}{ signal = wxSIGNONE}, \param{int }{flags = wxKILL\_NOCHILDREN}}
 163
 164 Send the specified signal to the given process. Possible signal values are:
 165
 166 \begin{verbatim}
 167 enum wxSignal
 168 {
 169     wxSIGNONE = 0,  // verify if the process exists under Unix
 170     wxSIGHUP,
 171     wxSIGINT,
 172     wxSIGQUIT,
 173     wxSIGILL,
 174     wxSIGTRAP,
 175     wxSIGABRT,
 176     wxSIGEMT,
 177     wxSIGFPE,
 178     wxSIGKILL,      // forcefully kill, dangerous!
 179     wxSIGBUS,
 180     wxSIGSEGV,
 181     wxSIGSYS,
 182     wxSIGPIPE,
 183     wxSIGALRM,
 184     wxSIGTERM       // terminate the process gently
 185 };
 186 \end{verbatim}
 187
 188 {\tt wxSIGNONE}, {\tt wxSIGKILL} and {\tt wxSIGTERM} have the same meaning
 189 under both Unix and Windows but all the other signals are equivalent to
 190 {\tt wxSIGTERM} under Windows.
 191
 192 The {\it flags} parameter can be wxKILL\_NOCHILDREN (the default),
 193 or wxKILL\_CHILDREN, in which case the child processes of this
 194 process will be killed too. Note that under Unix, for wxKILL\_CHILDREN
 195 to work you should have created the process passing wxEXEC\_MAKE\_GROUP\_LEADER.
 196
 197 Returns the element of {\tt wxKillError} enum:
 198
 199 \begin{verbatim}
 200 enum wxKillError
 201 {
 202     wxKILL_OK,              // no error
 203     wxKILL_BAD_SIGNAL,      // no such signal
 204     wxKILL_ACCESS_DENIED,   // permission denied
 205     wxKILL_NO_PROCESS,      // no such process
 206     wxKILL_ERROR            // another, unspecified error
 207 };
 208 \end{verbatim}
 209
 210 \wxheading{See also}
 211
 212 \helpref{wxProcess::Exists}{wxprocessexists},\rtfsp
 213 \helpref{wxKill}{wxkill},\rtfsp
 214 \helpref{Exec sample}{sampleexec}
 215
 216 \membersection{wxProcess::Exists}\label{wxprocessexists}
 217
 218 \func{static bool}{Exists}{\param{int}{ pid}}
 219
 220 Returns {\tt true} if the given process exists in the system.
 221
 222 \wxheading{See also}
 223
 224 \helpref{wxProcess::Kill}{wxprocesskill},\rtfsp
 225 \helpref{Exec sample}{sampleexec}
 226
 227 \membersection{wxProcess::OnTerminate}\label{wxprocessonterminate}
 228
 229 \func{void}{OnTerminate}{\param{int}{ pid}, \param{int}{ status}}
 230
 231 It is called when the process with the pid {\it pid} finishes.
 232 It raises a wxWidgets event when it isn't overridden.
 233
 234 \docparam{pid}{The pid of the process which has just terminated.}
 235
 236 \docparam{status}{The exit code of the process.}
 237
 238 \membersection{wxProcess::Open}\label{wxprocessopen}
 239
 240 \func{static wxProcess *}{Open}{\param{const wxString\& }{cmd}, \param{int }{flags = wxEXEC\_ASYNC}}
 241
 242 This static method replaces the standard {\tt popen()} function: it launches
 243 the process specified by the {\it cmd} parameter and returns the wxProcess
 244 object which can be used to retrieve the streams connected to the standard
 245 input, output and error output of the child process.
 246
 247 If the process couldn't be launched, {\tt NULL} is returned. Note that in any
 248 case the returned pointer should {\bf not} be deleted, rather the process
 249 object will be destroyed automatically when the child process terminates. This
 250 does mean that the child process should be told to quit before the main program
 251 exits to avoid memory leaks.
 252
 253 \wxheading{Parameters}
 254
 255 \docparam{cmd}{The command to execute, including optional arguments.}
 256 \docparam{flags}{The flags to pass to \helpref{wxExecute}{wxexecute}.
 257   NOTE: wxEXEC\_SYNC should not be used.}
 258
 259 \wxheading{Return value}
 260
 261 A pointer to new wxProcess object or {\tt NULL} on error.
 262
 263 \wxheading{See also}
 264
 265 \helpref{wxExecute}{wxexecute}
 266
 267 \membersection{wxProcess::GetPid}\label{wxprocessgetpid}
 268
 269 \constfunc{long}{GetPid}{\void}
 270
 271 Returns the process ID of the process launched by \helpref{Open}{wxprocessopen}.
 272
 273 \membersection{wxProcess::Redirect}\label{wxprocessredirect}
 274
 275 \func{void}{Redirect}{\void}
 276
 277 Turns on redirection. wxExecute will try to open a couple of pipes
 278 to catch the subprocess stdio. The caught input stream is returned by
 279 GetOutputStream() as a non-seekable stream. The caught output stream is returned
 280 by GetInputStream() as a non-seekable stream.
 281