class KProcess

Child process invocation, monitoring and control. More...

Definition#include <kprocess.h>
InheritsQObject (qt) [public ]
Inherited byKProcIO, KShellProcess
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Detailed Description

Child process invocation, monitoring and control.

General usage and features

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.

Communication with the child process

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):

QT signals:

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<<

KProcessoperator<< (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:
commSpecifies 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:
signoThe 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:
bufferThe data received.
buflenThe 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:
bufferThe data received.
buflenThe 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]