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Child process invocation, monitoring and control.
This class allows a KDE application to start child processes without having to worry about UN*X signal handling issues and zombie process reaping.
Basically, this class distinguishes three different ways of running child processes:
Starting a DontCare child process means that the application is not interested in any notification to determine whether the child process has already exited or not.
When the child process exits, the KProcess instance corresponding to it emits the Qt signal processExited().
Since this signal is not emitted from within a UN*X signal handler, arbitrary function calls can be made.
Be aware: When the KProcess objects gets destructed, the child process will be killed if it is still running! This means in particular, that you cannot use a KProcess on the stack with KProcess::NotifyOnExit.
KProcess also provides several functions for determining the exit status and the pid of the child process it represents.
Furthermore it is possible to supply command-line arguments to the process in a clean fashion (no null -- terminated stringlists and such...)
A small usage example:
KProcess proc; proc << "my_executable"; proc << "These" << "are" << "the" << "command" << "line" << "args"; QApplication::connect(&proc, SIGNAL(processExited(KProcess *)), pointer_to_my_object, SLOT(my_objects_slot)); proc.start(); |
This will start "my_executable" with the commandline arguments "These"...
When the child process exits, the respective Qt signal will be emitted.
KProcess supports communication with the child process through stdin/stdout/stderr.
The following functions are provided for getting data from the child process or sending data to the child's stdin (For more information, have a look at the documentation of each function):
See also: KProcIO
| enum Communication { NoCommunication = 0, Stdin = 1, Stdout = 2, Stderr = 4, AllOutput = 6, All = 7, NoRead } | Communication |
Modes in which the communication channel can be opened.
If communication for more than one channel is required,
the values have to be or'ed together, for example to get
communication with stdout as well as with stdin, you would
specify Stdin @p | Stdout
If NoRead is specified in conjunction with Stdout,
no data is actually read from Stdout but only
the signal childOutput(int fd) is emitted.
| enum RunMode { DontCare, NotifyOnExit, Block } | RunMode |
Run-modes for a child process.
See also: KProcess
| KProcess ()
| KProcess |
| ~KProcess ()
| ~KProcess |
[virtual]
Destructor:
If the process is running when the destructor for this class
is called, the child process is killed with a SIGKILL, but
only if the run mode is not of type DontCare.
Processes started as DontCare keep running anyway.
| bool setExecutable (const QString& proc)
| setExecutable |
The use of this function is now deprecated. -- Please use the "operator<<" instead of "setExecutable".
Sets the executable to be started with this KProcess object. Returns false if the process is currently running (in that case the executable remains unchanged.)
See also: operator<<
| KProcess & operator<< (const QString& arg)
| operator<< |
Sets the executable and the command line argument list for this process.
For example, doing an "ls -l /usr/local/bin" can be achieved by:
KProcess p; ... p << "ls" << "-l" << "/usr/local/bin" |
| void clearArguments ()
| clearArguments |
Clear a command line argument list that has been set by using the "operator<<".
| bool start (RunMode runmode = NotifyOnExit,
Communication comm = NoCommunication)
| start |
[virtual]
Start the process. For a detailed description of the various run modes and communication semantics, have a look at the general description of the KProcess class.
The following problems could cause KProcess:start() to
return false:
Parameters:
| comm | Specifies which communication links should be established to the child process (stdin/stdout/stderr). By default, no communication takes place and the respective communication signals will never get emitted. |
Returns: true on success, false on error
(see above for error conditions)
| bool kill (int signo = SIGTERM)
| kill |
[virtual]
Stop the process (by sending it a signal).
Parameters:
| signo | The signal to send. The default is SIGTERM. |
Returns: true if the signal was delivered successfully.
| bool isRunning ()
| isRunning |
[const]
Returns: true if the process is (still) considered to be running
| pid_t pid ()
| pid |
[const]
Returns the process id of the process.
If it is called after the process has exited, it returns the process id of the last child process that was created by this instance of KProcess.
Calling it before any child process has been started by this KProcess instance causes pid() to return 0.
| pid_t getPid ()
| getPid |
[const]
Use pid().
| void suspend ()
| suspend |
Suspend processing of data from stdout of the child process.
| void resume ()
| resume |
Resume processing of data from stdout of the child process.
| bool normalExit ()
| normalExit |
[const]
Note that you should check KProcess::exitStatus() to determine whether the process completed its task successfull or not.
Returns: true if the process has already finished and has exited
"voluntarily", ie: it has not been killed by a signal.
| int exitStatus ()
| exitStatus |
[const]
Retrieve the exit status of the process.
Please use
KProcess::normalExit() to check whether the process has exited
cleanly (i.e., KProcess::normalExit() returns true) before calling
this function because if the process did not exit normally,
it does not have a valid exit status.
| bool writeStdin (const char *buffer, int buflen)
| writeStdin |
Transmit data to the child process's stdin.
KProcess::writeStdin may return false in the following cases:
Please note that the data is sent to the client asynchronousely, so when this function returns, the data might not have been processed by the child process.
If all the data has been sent to the client, the signal wroteStdin() will be emitted.
Please note that you must not free "buffer" or call writeStdin() again until either a wroteStdin() signal indicates that the data has been sent or a processHasExited() signal shows that the child process is no longer alive...
| bool closeStdin ()
| closeStdin |
This causes the stdin file descriptor of the child process to be closed indicating an "EOF" to the child.
Returns: false if no communication to the process's stdin
had been specified in the call to start().
| bool closeStdout ()
| closeStdout |
This causes the stdout file descriptor of the child process to be closed.
Returns: false if no communication to the process's stdout
had been specified in the call to start().
| bool closeStderr ()
| closeStderr |
This causes the stderr file descriptor of the child process to be closed.
Returns: false if no communication to the process's stderr
had been specified in the call to start().
| QStrList * args ()
| args |
Lets you see what your arguments are for debugging.
| void setRunPrivileged (bool keepPrivileges)
| setRunPrivileged |
Controls whether the started process should drop any setuid/segid privileges or whether it should keep them
The default is false : drop privileges
| bool runPrivileged ()
| runPrivileged |
[const]
Returns whether the started process will drop any setuid/segid privileges or whether it will keep them
| void detach ()
| detach |
Detaches KProcess from child process. All communication is closed. No exit notification is emitted any more for the child process. Deleting the KProcess will no longer kill the child process. Note that the current process remains the parent process of the child process.
| void processExited (KProcess *proc)
| processExited |
[signal]
Emitted after the process has terminated when
the process was run in the NotifyOnExit (==default option to
start()) or the Block mode.
| void receivedStdout (KProcess *proc, char *buffer, int buflen)
| receivedStdout |
[signal]
Emitted, when output from the child process has been received on stdout.
To actually get these signals, the respective communication link (stdout/stderr) has to be turned on in start().
You should copy the information contained in buffer to your private
data structures before returning from this slot.
Parameters:
| buffer | The data received. |
| buflen | The number of bytes that are available. |
| void receivedStdout (int fd, int &len)
| receivedStdout |
[signal]
Emitted when output from the child process has been received on stdout.
To actually get these signals, the respective communications link
(stdout/stderr) has to be turned on in start() and the
NoRead flag should have been passed.
You will need to explicitly call resume() after your call to start() to begin processing data from the child process's stdout. This is to ensure that this signal is not emitted when no one is connected to it, otherwise this signal will not be emitted.
The data still has to be read from file descriptor fd.
| void receivedStderr (KProcess *proc, char *buffer, int buflen)
| receivedStderr |
[signal]
Emitted, when output from the child process has been received on stderr. To actually get these signals, the respective communication link (stdout/stderr) has to be turned on in start().
You should copy the information contained in buffer to your private
data structures before returning from this slot.
Parameters:
| buffer | The data received. |
| buflen | The number of bytes that are available. |
| void wroteStdin (KProcess *proc)
| wroteStdin |
[signal]
Emitted after all the data that has been specified by a prior call to writeStdin() has actually been written to the child process.
| void slotChildOutput (int fdno)
| slotChildOutput |
[protected slots slot]
This slot gets activated when data from the child's stdout arrives. It usually calls "childOutput"
| void slotChildError (int fdno)
| slotChildError |
[protected slots slot]
This slot gets activated when data from the child's stderr arrives. It usually calls "childError"
| void slotSendData (int dummy)
| slotSendData |
[protected slots slot]
Called when another bulk of data can be sent to the child's stdin. If there is no more data to be sent to stdin currently available, this function must disable the QSocketNotifier "innot".
| QStrList arguments | arguments |
[protected]
| RunMode run_mode | run_mode |
[protected]
| bool runs | runs |
[protected]
| pid_t pid_ | pid_ |
[protected]
| int status | status |
[protected]
| bool keepPrivs | keepPrivs |
[protected]
| int setupCommunication (Communication comm)
| setupCommunication |
[protected virtual]
This function is called from "KProcess::start" right before a "fork" takes place. According to the "comm" parameter this function has to initialize the "in", "out" and "err" data member of KProcess.
This function should return 0 if setting the needed communication channels was successful.
The default implementation is to create UNIX STREAM sockets for the communication, but you could overload this function and establish a TCP/IP communication for network communication, for example.
| int commSetupDoneP ()
| commSetupDoneP |
[protected virtual]
Called right after a (successful) fork on the parent side. This function will usually do some communications cleanup, like closing the reading end of the "stdin" communication channel.
Furthermore, it must also create the QSocketNotifiers "innot", "outnot" and "errnot" and connect their Qt slots to the respective KProcess member functions.
For a more detailed explanation, it is best to have a look at the default implementation of "setupCommunication" in kprocess.cpp.
| int commSetupDoneC ()
| commSetupDoneC |
[protected virtual]
Called right after a (successful) fork, but before an "exec" on the child process' side. It usually just closes the unused communication ends of "in", "out" and "err" (like the writing end of the "in" communication channel.
| void processHasExited (int state)
| processHasExited |
[protected virtual]
Immediately called after a process has exited. This function normally calls commClose to close all open communication channels to this process and emits the "processExited" signal (if the process was not running in the "DontCare" mode).
| void commClose ()
| commClose |
[protected virtual]
Should clean up the communication links to the child after it has exited. Should be called from "processHasExited".
| int out[2] | out[2] |
[protected]
| int in[2] | in[2] |
[protected]
| int err[2] | err[2] |
[protected]
| QSocketNotifier * innot | innot |
[protected]
| QSocketNotifier * outnot | outnot |
[protected]
| QSocketNotifier * errnot | errnot |
[protected]
| Communication communication | communication |
[protected]
| int childOutput (int fdno)
| childOutput |
[protected]
Called by "slotChildOutput" this function copies data arriving from the child process's stdout to the respective buffer and emits the signal "receivedStderr".
| int childError (int fdno)
| childError |
[protected]
Called by "slotChildOutput" this function copies data arriving from the child process's stdout to the respective buffer and emits the signal "receivedStderr"
| const char * input_data | input_data |
[protected]
| int input_sent | input_sent |
[protected]
| int input_total | input_total |
[protected]
| friend class KProcessController | KProcessController |
[protected]