Q3Process Class Reference
[Qt3Support module]

Detailed Description

The Q3Process class is used to start external programs and to communicate with them.

You can write to the started program's standard input, and can read the program's standard output and standard error. You can pass command line arguments to the program either in the constructor or with setArguments() or addArgument(). The program's working directory can be set with setWorkingDirectory(). If you need to set up environment variables pass them to the start() or launch() functions (see below). The processExited() signal is emitted if the program exits. The program's exit status is available from exitStatus(), although you could simply call normalExit() to see if the program terminated normally.

There are two different ways to start a process. If you just want to run a program, optionally passing data to its standard input at the beginning, use one of the launch() functions. If you want full control of the program's standard input (especially if you don't know all the data you want to send to standard input at the beginning), use the start() function.

If you use start() you can write to the program's standard input using writeToStdin() and you can close the standard input with closeStdin(). The wroteToStdin() signal is emitted if the data sent to standard input has been written. You can read from the program's standard output using readStdout() or readLineStdout(). These functions return an empty QByteArray if there is no data to read. The readyReadStdout() signal is emitted when there is data available to be read from standard output. Standard error has a set of functions that correspond to the standard output functions, i.e. readStderr(), readLineStderr() and readyReadStderr().

If you use one of the launch() functions the data you pass will be sent to the program's standard input which will be closed once all the data has been written. You should not use writeToStdin() or closeStdin() if you use launch(). If you need to send data to the program's standard input after it has started running use start() instead of launch().

Both start() and launch() can accept a string list of strings each of which has the format, key=value, where the keys are the names of environment variables.

You can test to see if a program is running with isRunning(). The program's process identifier is available from processIdentifier(). If you want to terminate a running program use tryTerminate(), but note that the program may ignore this. If you really want to terminate the program, without it having any chance to clean up, you can use kill().

Although you may need quotes for a file named on the command line (e.g. if it contains spaces) you shouldn't use extra quotes for arguments passed to addArgument() or setArguments().

The readyReadStdout() signal is emitted when there is new data on standard output. This happens asynchronously: you don't know if more data will arrive later.

In the above example you could connect the processExited() signal to the slot UicManager::readFromStdout() instead. If you do so, you will be certain that all the data is available when the slot is called. On the other hand, you must wait until the process has finished before doing any processing.

Note that if you are expecting a lot of output from the process, you may hit platform-dependent limits to the pipe buffer size. The solution is to make sure you connect to the output, e.g. the readyReadStdout() and readyReadStderr() signals and read the data as soon as it becomes available.

Please note that Q3Process does not emulate a shell. This means that Q3Process does not do any expansion of arguments: a '*' is passed as a '*' to the program and is not replaced by all the files, a '$HOME' is also passed literally and is not replaced by the environment variable HOME and the special characters for IO redirection ('>', '|', etc.) are also passed literally and do not have the special meaning as they have in a shell.

Also note that Q3Process does not emulate a terminal. This means that certain programs which need direct terminal control, do not work as expected with Q3Process. Such programs include console email programs (like pine and mutt) but also programs which require the user to enter a password (like su and ssh).

 QStringList list = myProcess.arguments();
 QStringList::Iterator it = list.begin();
 while( it != list.end() ) {
     myProcessing( *it );
     ++it;
 }

 process->tryTerminate();
 QTimer::singleShot( 5000, process, SLOT(kill()) );