QProcess 类

QProcess class is used to start external programs and to communicate with them. 更多...

Header: #include <QProcess>
qmake: QT += core
继承: QIODevice

注意: 此类的所有函数 可重入 .

公共类型

class CreateProcessArguments
typedef CreateProcessArgumentModifier
enum ExitStatus { NormalExit, CrashExit }
enum InputChannelMode { ManagedInputChannel, ForwardedInputChannel }
enum ProcessChannel { StandardOutput, StandardError }
enum ProcessChannelMode { SeparateChannels, MergedChannels, ForwardedChannels, ForwardedErrorChannel, ForwardedOutputChannel }
enum ProcessError { FailedToStart, Crashed, Timedout, WriteError, ReadError, UnknownError }
enum ProcessState { NotRunning, Starting, Running }

公共函数

QProcess (QObject * parent = nullptr)
virtual ~QProcess ()
QStringList arguments () const
void closeReadChannel (QProcess::ProcessChannel channel )
void closeWriteChannel ()
QProcess::CreateProcessArgumentModifier createProcessArgumentsModifier () const
QProcess::ProcessError error () const
int exitCode () const
QProcess::ExitStatus exitStatus () const
QProcess::InputChannelMode inputChannelMode () const
QString nativeArguments () const
QProcess::ProcessChannelMode processChannelMode () const
QProcessEnvironment processEnvironment () const
qint64 processId () const
QString program () const
QByteArray readAllStandardError ()
QByteArray readAllStandardOutput ()
QProcess::ProcessChannel readChannel () const
void setArguments (const QStringList & arguments )
void setCreateProcessArgumentsModifier (QProcess::CreateProcessArgumentModifier modifier )
void setInputChannelMode (QProcess::InputChannelMode mode )
void setNativeArguments (const QString & arguments )
void setProcessChannelMode (QProcess::ProcessChannelMode mode )
void setProcessEnvironment (const QProcessEnvironment & environment )
void setProgram (const QString & program )
void setReadChannel (QProcess::ProcessChannel channel )
void setStandardErrorFile (const QString & fileName , QIODevice::OpenMode mode = Truncate)
void setStandardInputFile (const QString & fileName )
void setStandardOutputFile (const QString & fileName , QIODevice::OpenMode mode = Truncate)
void setStandardOutputProcess (QProcess * destination )
void setWorkingDirectory (const QString & dir )
void start (const QString & program , const QStringList & arguments , QIODevice::OpenMode mode = ReadWrite)
void start (const QString & command , QIODevice::OpenMode mode = ReadWrite)
void start (QIODevice::OpenMode mode = ReadWrite)
bool startDetached (qint64 * pid = nullptr)
QProcess::ProcessState state () const
bool waitForFinished (int msecs = 30000)
bool waitForStarted (int msecs = 30000)
QString workingDirectory () const

重实现公共函数

virtual bool atEnd () const override
virtual qint64 bytesAvailable () const override
virtual qint64 bytesToWrite () const override
virtual bool canReadLine () const override
virtual void close () override
virtual bool isSequential () const override
virtual bool open (QIODevice::OpenMode mode = ReadWrite) override
virtual bool waitForBytesWritten (int msecs = 30000) override
virtual bool waitForReadyRead (int msecs = 30000) override

公共槽

void kill ()
void terminate ()

信号

void errorOccurred (QProcess::ProcessError error )
void finished (int exitCode , QProcess::ExitStatus exitStatus )
void readyReadStandardError ()
void readyReadStandardOutput ()
void started ()
void stateChanged (QProcess::ProcessState newState )

静态公共成员

int execute (const QString & program , const QStringList & arguments )
int execute (const QString & command )
QString nullDevice ()
bool startDetached (const QString & program , const QStringList & arguments , const QString & workingDirectory = QString(), qint64 * pid = nullptr)
bool startDetached (const QString & command )
const QMetaObject staticMetaObject
QStringList systemEnvironment ()
  • 10 static public members inherited from QObject

保护函数

void setProcessState (QProcess::ProcessState state )
virtual void setupChildProcess ()

重实现保护函数

virtual qint64 readData (char * data , qint64 maxlen ) override
virtual qint64 writeData (const char * data , qint64 len ) override
typedef Q_PID

额外继承成员

详细描述

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

运行进程

要启动进程,把希望运行程序名称和命令行自变量,作为自变量传递给 start ()。自变量作为单字符串被提供采用 QStringList .

Alternatively, you can set the program to run with setProgram () 和 setArguments (), and then call start () 或 open ().

For example, the following code snippet runs the analog clock example in the Fusion style on X11 platforms by passing strings containing "-style" and "fusion" as two items in the list of arguments:

    QObject *parent;
    ...
    QString program = "./path/to/Qt/examples/widgets/analogclock";
    QStringList arguments;
    arguments << "-style" << "fusion";
    QProcess *myProcess = new QProcess(parent);
    myProcess->start(program, arguments);
							

QProcess then enters the Starting state, and when the program has started, QProcess enters the Running state and emits started ().

QProcess allows you to treat a process as a sequential I/O device. You can write to and read from the process just as you would access a network connection using QTcpSocket . You can then write to the process's standard input by calling write (), and read the standard output by calling read (), readLine (),和 getChar (). Because it inherits QIODevice , QProcess can also be used as an input source for QXmlReader , or for generating data to be uploaded using QNetworkAccessManager .

When the process exits, QProcess reenters the NotRunning state (the initial state), and emits finished ().

finished () signal provides the exit code and exit status of the process as arguments, and you can also call exitCode () to obtain the exit code of the last process that finished, and exitStatus () to obtain its exit status. If an error occurs at any point in time, QProcess 将发射 errorOccurred () signal. You can also call error () to find the type of error that occurred last, and state () to find the current process state.

注意: QProcess is not supported on VxWorks , iOS, tvOS, watchOS, or the Universal Windows Platform.

凭借通道通信

Processes have two predefined output channels: The standard output channel ( stdout ) supplies regular console output, and the standard error channel ( stderr ) usually supplies the errors that are printed by the process. These channels represent two separate streams of data. You can toggle between them by calling setReadChannel (). QProcess 发射 readyRead () when data is available on the current read channel. It also emits readyReadStandardOutput () when new standard output data is available, and when new standard error data is available, readyReadStandardError () is emitted. Instead of calling read (), readLine (),或 getChar (), you can explicitly read all data from either of the two channels by calling readAllStandardOutput () 或 readAllStandardError ().

The terminology for the channels can be misleading. Be aware that the process's output channels correspond to QProcess 's read channels, whereas the process's input channels correspond to QProcess 's write channels. This is because what we read using QProcess is the process's output, and what we write becomes the process's input.

QProcess can merge the two output channels, so that standard output and standard error data from the running process both use the standard output channel. Call setProcessChannelMode () with MergedChannels before starting the process to activate this feature. You also have the option of forwarding the output of the running process to the calling, main process, by passing ForwardedChannels as the argument. It is also possible to forward only one of the output channels - typically one would use ForwardedErrorChannel , but ForwardedOutputChannel also exists. Note that using channel forwarding is typically a bad idea in GUI applications - you should present errors graphically instead.

Certain processes need special environment settings in order to operate. You can set environment variables for your process by calling setProcessEnvironment (). To set a working directory, call setWorkingDirectory (). By default, processes are run in the current working directory of the calling process.

The positioning and the screen Z-order of windows belonging to GUI applications started with QProcess are controlled by the underlying windowing system. For Qt 5 applications, the positioning can be specified using the -qwindowgeometry command line option; X11 applications generally accept a -geometry command line option.

注意: On QNX, setting the working directory may cause all application threads, with the exception of the QProcess caller thread, to temporarily freeze during the spawning process, owing to a limitation in the operating system.

同步进程 API

QProcess provides a set of functions which allow it to be used without an event loop, by suspending the calling thread until certain signals are emitted:

Calling these functions from the main thread (the thread that calls QApplication::exec ()) may cause your user interface to freeze.

The following example runs gzip to compress the string "Qt rocks!", without an event loop:

    QProcess gzip;
    gzip.start("gzip", QStringList() << "-c");
    if (!gzip.waitForStarted())
        return false;
    gzip.write("Qt rocks!");
    gzip.closeWriteChannel();
    if (!gzip.waitForFinished())
        return false;
    QByteArray result = gzip.readAll();
							

Windows 用户注意事项

Some Windows commands (for example, dir ) are not provided by separate applications, but by the command interpreter itself. If you attempt to use QProcess to execute these commands directly, it won't work. One possible solution is to execute the command interpreter itself ( cmd.exe on some Windows systems), and ask the interpreter to execute the desired command.

另请参阅 QBuffer , QFile ,和 QTcpSocket .

成员类型文档编制

typedef QProcess:: CreateProcessArgumentModifier

注意: This typedef is only available on desktop Windows.

在 Windows, QProcess uses the Win32 API function CreateProcess to start child processes. While QProcess provides a comfortable way to start processes without worrying about platform details, it is in some cases desirable to fine-tune the parameters that are passed to CreateProcess . This is done by defining a CreateProcessArgumentModifier function and passing it to setCreateProcessArgumentsModifier .

CreateProcessArgumentModifier function takes one parameter: a pointer to a CreateProcessArguments struct. The members of this struct will be passed to CreateProcess after the CreateProcessArgumentModifier function is called.

The following example demonstrates how to pass custom flags to CreateProcess . When starting a console process B from a console process A, QProcess will reuse the console window of process A for process B by default. In this example, a new console window with a custom color scheme is created for the child process B instead.

    QProcess process;
    process.setCreateProcessArgumentsModifier([] (QProcess::CreateProcessArguments *args)
    {
        args->flags |= CREATE_NEW_CONSOLE;
        args->startupInfo->dwFlags &= ~STARTF_USESTDHANDLES;
        args->startupInfo->dwFlags |= STARTF_USEFILLATTRIBUTE;
        args->startupInfo->dwFillAttribute = BACKGROUND_BLUE | FOREGROUND_RED
                                           | FOREGROUND_INTENSITY;
    });
    process.start("C:\\Windows\\System32\\cmd.exe", QStringList() << "/k" << "title" << "The Child Process");
							

另请参阅 QProcess::CreateProcessArguments and setCreateProcessArgumentsModifier ().

enum QProcess:: ExitStatus

This enum describes the different exit statuses of QProcess .

常量 描述
QProcess::NormalExit 0 The process exited normally.
QProcess::CrashExit 1 The process crashed.

另请参阅 exitStatus ().

enum QProcess:: InputChannelMode

This enum describes the process input channel modes of QProcess . Pass one of these values to setInputChannelMode () to set the current write channel mode.

常量 描述
QProcess::ManagedInputChannel 0 QProcess manages the input of the running process. This is the default input channel mode of QProcess .
QProcess::ForwardedInputChannel 1 QProcess forwards the input of the main process onto the running process. The child process reads its standard input from the same source as the main process. Note that the main process must not try to read its standard input while the child process is running.

This enum was introduced or modified in Qt 5.2.

另请参阅 setInputChannelMode ().

enum QProcess:: ProcessChannel

This enum describes the process channels used by the running process. Pass one of these values to setReadChannel () to set the current read channel of QProcess .

常量 描述
QProcess::StandardOutput 0 The standard output (stdout) of the running process.
QProcess::StandardError 1 The standard error (stderr) of the running process.

另请参阅 setReadChannel ().

enum QProcess:: ProcessChannelMode

This enum describes the process output channel modes of QProcess . Pass one of these values to setProcessChannelMode () to set the current read channel mode.

常量 描述
QProcess::SeparateChannels 0 QProcess manages the output of the running process, keeping standard output and standard error data in separate internal buffers. You can select the QProcess 's current read channel by calling setReadChannel (). This is the default channel mode of QProcess .
QProcess::MergedChannels 1 QProcess merges the output of the running process into the standard output channel ( stdout ). The standard error channel ( stderr ) will not receive any data. The standard output and standard error data of the running process are interleaved.
QProcess::ForwardedChannels 2 QProcess forwards the output of the running process onto the main process. Anything the child process writes to its standard output and standard error will be written to the standard output and standard error of the main process.
QProcess::ForwardedErrorChannel 4 QProcess manages the standard output of the running process, but forwards its standard error onto the main process. This reflects the typical use of command line tools as filters, where the standard output is redirected to another process or a file, while standard error is printed to the console for diagnostic purposes. (This value was introduced in Qt 5.2.)
QProcess::ForwardedOutputChannel 3 Complementary to ForwardedErrorChannel. (This value was introduced in Qt 5.2.)

注意: Windows intentionally suppresses output from GUI-only applications to inherited consoles. This does not apply to output redirected to files or pipes. To forward the output of GUI-only applications on the console nonetheless, you must use SeparateChannels and do the forwarding yourself by reading the output and writing it to the appropriate output channels.

另请参阅 setProcessChannelMode ().

enum QProcess:: ProcessError

This enum describes the different types of errors that are reported by QProcess .

常量 描述
QProcess::FailedToStart 0 The process failed to start. Either the invoked program is missing, or you may have insufficient permissions to invoke the program.
QProcess::Crashed 1 The process crashed some time after starting successfully.
QProcess::Timedout 2 The last waitFor...() function timed out. The state of QProcess is unchanged, and you can try calling waitFor...() again.
QProcess::WriteError 4 An error occurred when attempting to write to the process. For example, the process may not be running, or it may have closed its input channel.
QProcess::ReadError 3 An error occurred when attempting to read from the process. For example, the process may not be running.
QProcess::UnknownError 5 An unknown error occurred. This is the default return value of error ().

另请参阅 error ().

enum QProcess:: ProcessState

此枚举描述不同状态,为 QProcess .

常量 描述
QProcess::NotRunning 0 The process is not running.
QProcess::Starting 1 The process is starting, but the program has not yet been invoked.
QProcess::Running 2 The process is running and is ready for reading and writing.

另请参阅 state ().

成员函数文档编制

QProcess:: QProcess ( QObject * parent = nullptr)

构造 QProcess 对象采用给定 parent .

[virtual] QProcess:: ~QProcess ()

销毁 QProcess object, i.e., killing the process.

Note that this function will not return until the process is terminated.

QStringList QProcess:: arguments () const

Returns the command line arguments the process was last started with.

This function was introduced in Qt 5.0.

另请参阅 setArguments () 和 start ().

[override virtual] bool QProcess:: atEnd () const

Reimplemented from QIODevice::atEnd ().

返回 true if the process is not running, and no more data is available for reading; otherwise returns false .

[override virtual] qint64 QProcess:: bytesAvailable () const

Reimplemented from QIODevice::bytesAvailable ().

[override virtual] qint64 QProcess:: bytesToWrite () const

Reimplemented from QIODevice::bytesToWrite ().

[override virtual] bool QProcess:: canReadLine () const

Reimplemented from QIODevice::canReadLine ().

This function operates on the current read channel.

另请参阅 readChannel () 和 setReadChannel ().

[override virtual] void QProcess:: close ()

Reimplemented from QIODevice::close ().

Closes all communication with the process and kills it. After calling this function, QProcess will no longer emit readyRead (), and data can no longer be read or written.

void QProcess:: closeReadChannel ( QProcess::ProcessChannel channel )

Closes the read channel channel . After calling this function, QProcess will no longer receive data on the channel. Any data that has already been received is still available for reading.

Call this function to save memory, if you are not interested in the output of the process.

另请参阅 closeWriteChannel () 和 setReadChannel ().

void QProcess:: closeWriteChannel ()

Schedules the write channel of QProcess to be closed. The channel will close once all data has been written to the process. After calling this function, any attempts to write to the process will fail.

Closing the write channel is necessary for programs that read input data until the channel has been closed. For example, the program "more" is used to display text data in a console on both Unix and Windows. But it will not display the text data until QProcess 's write channel has been closed. Example:

QProcess more;
more.start("more");
more.write("Text to display");
more.closeWriteChannel();
// QProcess will emit readyRead() once "more" starts printing
							

The write channel is implicitly opened when start () 被调用。

另请参阅 closeReadChannel ().

QProcess::CreateProcessArgumentModifier QProcess:: createProcessArgumentsModifier () const

Returns a previously set CreateProcess modifier function.

注意: This function is available only on the Windows platform.

This function was introduced in Qt 5.7.

另请参阅 setCreateProcessArgumentsModifier () 和 QProcess::CreateProcessArgumentModifier .

QProcess::ProcessError QProcess:: error () const

Returns the type of error that occurred last.

另请参阅 state ().

[signal] void QProcess:: errorOccurred ( QProcess::ProcessError error )

This signal is emitted when an error occurs with the process. The specified error describes the type of error that occurred.

This function was introduced in Qt 5.6.

[static] int QProcess:: execute (const QString & program , const QStringList & arguments )

Starts the program program 采用自变量 arguments in a new process, waits for it to finish, and then returns the exit code of the process. Any data the new process writes to the console is forwarded to the calling process.

The environment and working directory are inherited from the calling process.

Argument handling is identical to the respective start () overload.

If the process cannot be started, -2 is returned. If the process crashes, -1 is returned. Otherwise, the process' exit code is returned.

另请参阅 start ().

[static] int QProcess:: execute (const QString & command )

这是重载函数。

Starts the program command in a new process, waits for it to finish, and then returns the exit code.

Argument handling is identical to the respective start () overload.

After the command string has been split and unquoted, this function behaves like the overload which takes the arguments as a string list.

另请参阅 start ().

int QProcess:: exitCode () const

Returns the exit code of the last process that finished.

This value is not valid unless exitStatus () 返回 NormalExit .

QProcess::ExitStatus QProcess:: exitStatus () const

Returns the exit status of the last process that finished.

On Windows, if the process was terminated with TerminateProcess() from another application, this function will still return NormalExit unless the exit code is less than 0.

This function was introduced in Qt 4.1.

[signal] void QProcess:: finished ( int exitCode , QProcess::ExitStatus exitStatus )

This signal is emitted when the process finishes. exitCode is the exit code of the process (only valid for normal exits), and exitStatus is the exit status. After the process has finished, the buffers in QProcess are still intact. You can still read any data that the process may have written before it finished.

注意: Signal finished 在此类中被重载。通过使用函数指针句法连接到此信号,Qt 提供用于获得如此范例展示的函数指针的方便帮助程序:

connect(process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
    [=](int exitCode, QProcess::ExitStatus exitStatus){ /* ... */ });
							

另请参阅 exitStatus ().

QProcess::InputChannelMode QProcess:: inputChannelMode () const

Returns the channel mode of the QProcess standard input channel.

This function was introduced in Qt 5.2.

另请参阅 setInputChannelMode () 和 InputChannelMode .

[override virtual] bool QProcess:: isSequential () const

Reimplemented from QIODevice::isSequential ().

[slot] void QProcess:: kill ()

Kills the current process, causing it to exit immediately.

On Windows, kill() uses TerminateProcess, and on Unix and macOS , the SIGKILL signal is sent to the process.

另请参阅 terminate ().

QString QProcess:: nativeArguments () const

Returns the additional native command line arguments for the program.

注意: This function is available only on the Windows platform.

This function was introduced in Qt 4.7.

另请参阅 setNativeArguments ().

[static] QString QProcess:: nullDevice ()

The null device of the operating system.

The returned file path uses native directory separators.

This function was introduced in Qt 5.2.

另请参阅 QProcess::setStandardInputFile (), QProcess::setStandardOutputFile (),和 QProcess::setStandardErrorFile ().

[override virtual] bool QProcess:: open ( QIODevice::OpenMode mode = ReadWrite)

Reimplemented from QIODevice::open ().

Starts the program set by setProgram () with arguments set by setArguments ()。 OpenMode is set to mode .

This method is an alias for start (), and exists only to fully implement the interface defined by QIODevice .

另请参阅 start (), setProgram (),和 setArguments ().

QProcess::ProcessChannelMode QProcess:: processChannelMode () const

Returns the channel mode of the QProcess standard output and standard error channels.

This function was introduced in Qt 4.2.

另请参阅 setProcessChannelMode (), ProcessChannelMode ,和 setReadChannel ().

QProcessEnvironment QProcess:: processEnvironment () const

Returns the environment that QProcess will pass to its child process, or an empty object if no environment has been set using setEnvironment() or setProcessEnvironment (). If no environment has been set, the environment of the calling process will be used.

This function was introduced in Qt 4.6.

另请参阅 setProcessEnvironment (), setEnvironment (),和 QProcessEnvironment::isEmpty ().

qint64 QProcess:: processId () const

Returns the native process identifier for the running process, if available. If no process is currently running, 0 被返回。

This function was introduced in Qt 5.3.

QString QProcess:: program () const

Returns the program the process was last started with.

This function was introduced in Qt 5.0.

另请参阅 setProgram () 和 start ().

QByteArray QProcess:: readAllStandardError ()

Regardless of the current read channel, this function returns all data available from the standard error of the process as a QByteArray .

另请参阅 readyReadStandardError (), readAllStandardOutput (), readChannel (),和 setReadChannel ().

QByteArray QProcess:: readAllStandardOutput ()

Regardless of the current read channel, this function returns all data available from the standard output of the process as a QByteArray .

另请参阅 readyReadStandardOutput (), readAllStandardError (), readChannel (),和 setReadChannel ().

QProcess::ProcessChannel QProcess:: readChannel () const

Returns the current read channel of the QProcess .

另请参阅 setReadChannel ().

[override virtual protected] qint64 QProcess:: readData ( char * data , qint64 maxlen )

Reimplemented from QIODevice::readData ().

[signal] void QProcess:: readyReadStandardError ()

This signal is emitted when the process has made new data available through its standard error channel ( stderr ). It is emitted regardless of the current read channel .

注意: 这是私有信号。它可以用于信号连接,但不能由用户发射。

另请参阅 readAllStandardError () 和 readChannel ().

[signal] void QProcess:: readyReadStandardOutput ()

This signal is emitted when the process has made new data available through its standard output channel ( stdout ). It is emitted regardless of the current read channel .

注意: 这是私有信号。它可以用于信号连接,但不能由用户发射。

另请参阅 readAllStandardOutput () 和 readChannel ().

void QProcess:: setArguments (const QStringList & arguments )

设置 arguments to pass to the called program when starting the process. This function must be called before start ().

This function was introduced in Qt 5.1.

另请参阅 start (), setProgram (),和 arguments ().

void QProcess:: setCreateProcessArgumentsModifier ( QProcess::CreateProcessArgumentModifier modifier )

设置 modifier CreateProcess Win32 API call. Pass QProcess::CreateProcessArgumentModifier() to remove a previously set one.

注意: This function is available only on the Windows platform and requires C++11.

This function was introduced in Qt 5.7.

另请参阅 createProcessArgumentsModifier () 和 QProcess::CreateProcessArgumentModifier .

void QProcess:: setInputChannelMode ( QProcess::InputChannelMode mode )

Sets the channel mode of the QProcess standard input channel to the mode specified. This mode will be used the next time start () 被调用。

This function was introduced in Qt 5.2.

另请参阅 inputChannelMode () 和 InputChannelMode .

void QProcess:: setNativeArguments (const QString & arguments )

这是重载函数。

Sets additional native command line arguments for the program.

On operating systems where the system API for passing command line arguments to a subprocess natively uses a single string, one can conceive command lines which cannot be passed via QProcess 's portable list-based API. In such cases this function must be used to set a string which is appended to the string composed from the usual argument list, with a delimiting space.

注意: This function is available only on the Windows platform.

This function was introduced in Qt 4.7.

另请参阅 nativeArguments ().

void QProcess:: setProcessChannelMode ( QProcess::ProcessChannelMode mode )

Sets the channel mode of the QProcess standard output and standard error channels to the mode specified. This mode will be used the next time start () is called. For example:

QProcess builder;
builder.setProcessChannelMode(QProcess::MergedChannels);
builder.start("make", QStringList() << "-j2");
if (!builder.waitForFinished())
    qDebug() << "Make failed:" << builder.errorString();
else
    qDebug() << "Make output:" << builder.readAll();
							

This function was introduced in Qt 4.2.

另请参阅 processChannelMode (), ProcessChannelMode ,和 setReadChannel ().

void QProcess:: setProcessEnvironment (const QProcessEnvironment & environment )

设置 environment that QProcess will pass to the child process.

For example, the following code adds the environment variable TMPDIR :

QProcess process;
QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
env.insert("TMPDIR", "C:\\MyApp\\temp"); // Add an environment variable
process.setProcessEnvironment(env);
process.start("myapp");
							

Note how, on Windows, environment variable names are case-insensitive.

This function was introduced in Qt 4.6.

另请参阅 processEnvironment (), QProcessEnvironment::systemEnvironment (),和 setEnvironment ().

[protected] void QProcess:: setProcessState ( QProcess::ProcessState state )

Sets the current state of the QProcess state specified.

另请参阅 state ().

void QProcess:: setProgram (const QString & program )

设置 program to use when starting the process. This function must be called before start ().

This function was introduced in Qt 5.1.

另请参阅 start (), setArguments (),和 program ().

void QProcess:: setReadChannel ( QProcess::ProcessChannel channel )

Sets the current read channel of the QProcess 到给定 channel . The current input channel is used by the functions read (), readAll (), readLine (),和 getChar (). It also determines which channel triggers QProcess to emit readyRead ().

另请参阅 readChannel ().

void QProcess:: setStandardErrorFile (const QString & fileName , QIODevice::OpenMode mode = Truncate)

Redirects the process' standard error to the file fileName . When the redirection is in place, the standard error read channel is closed: reading from it using read () will always fail, as will readAllStandardError (). The file will be appended to if mode is Append, otherwise, it will be truncated.

setStandardOutputFile () for more information on how the file is opened.

Note: if setProcessChannelMode () was called with an argument of QProcess::MergedChannels , this function has no effect.

This function was introduced in Qt 4.2.

另请参阅 setStandardInputFile (), setStandardOutputFile (),和 setStandardOutputProcess ().

void QProcess:: setStandardInputFile (const QString & fileName )

Redirects the process' standard input to the file indicated by fileName . When an input redirection is in place, the QProcess object will be in read-only mode (calling write () will result in error).

To make the process read EOF right away, pass nullDevice () here. This is cleaner than using closeWriteChannel () before writing any data, because it can be set up prior to starting the process.

If the file fileName does not exist at the moment start () is called or is not readable, starting the process will fail.

Calling setStandardInputFile() after the process has started has no effect.

This function was introduced in Qt 4.2.

另请参阅 setStandardOutputFile (), setStandardErrorFile (),和 setStandardOutputProcess ().

void QProcess:: setStandardOutputFile (const QString & fileName , QIODevice::OpenMode mode = Truncate)

Redirects the process' standard output to the file fileName . When the redirection is in place, the standard output read channel is closed: reading from it using read () will always fail, as will readAllStandardOutput ().

To discard all standard output from the process, pass nullDevice () here. This is more efficient than simply never reading the standard output, as no QProcess buffers are filled.

If the file fileName doesn't exist at the moment start () is called, it will be created. If it cannot be created, the starting will fail.

If the file exists and mode is QIODevice::Truncate , the file will be truncated. Otherwise (if mode is QIODevice::Append ), the file will be appended to.

Calling setStandardOutputFile() after the process has started has no effect.

This function was introduced in Qt 4.2.

另请参阅 setStandardInputFile (), setStandardErrorFile (),和 setStandardOutputProcess ().

void QProcess:: setStandardOutputProcess ( QProcess * destination )

Pipes the standard output stream of this process to the destination process' standard input.

The following shell command:

command1 | command2
							

Can be accomplished with QProcess with the following code:

QProcess process1;
QProcess process2;
process1.setStandardOutputProcess(&process2);
process1.start("command1");
process2.start("command2");
							

This function was introduced in Qt 4.2.

void QProcess:: setWorkingDirectory (const QString & dir )

Sets the working directory to dir . QProcess will start the process in this directory. The default behavior is to start the process in the working directory of the calling process.

注意: On QNX, this may cause all application threads to temporarily freeze.

另请参阅 workingDirectory () 和 start ().

[virtual protected] void QProcess:: setupChildProcess ()

This function is called in the child process context just before the program is executed on Unix or macOS (i.e., after fork() , but before execve() ). Reimplement this function to do last minute initialization of the child process. Example:

class SandboxProcess : public QProcess
{
    ...
 protected:
     void setupChildProcess() override;
    ...
};
void SandboxProcess::setupChildProcess()
{
    // Drop all privileges in the child process, and enter
    // a chroot jail.
#if defined Q_OS_UNIX
    ::setgroups(0, 0);
    ::chroot("/etc/safe");
    ::chdir("/");
    ::setgid(safeGid);
    ::setuid(safeUid);
    ::umask(0);
#endif
}
							

You cannot exit the process (by calling exit(), for instance) from this function. If you need to stop the program before it starts execution, your workaround is to emit finished () and then call exit().

警告: 此函数被调用由 QProcess on Unix and macOS only. On Windows and QNX, it is not called.

void QProcess:: start (const QString & program , const QStringList & arguments , QIODevice::OpenMode mode = ReadWrite)

Starts the given program in a new process, passing the command line arguments in arguments .

QProcess object will immediately enter the Starting state. If the process starts successfully, QProcess will emit started (); otherwise, errorOccurred () will be emitted.

注意: Processes are started asynchronously, which means the started () 和 errorOccurred () signals may be delayed. Call waitForStarted () to make sure the process has started (or has failed to start) and those signals have been emitted.

注意: No further splitting of the arguments is performed.

Windows: The arguments are quoted and joined into a command line that is compatible with the CommandLineToArgvW() Windows function. For programs that have different command line quoting requirements, you need to use setNativeArguments (). One notable program that does not follow the CommandLineToArgvW() rules is cmd.exe and, by consequence, all batch scripts.

OpenMode is set to mode .

QProcess object is already running a process, a warning may be printed at the console, and the existing process will continue running unaffected.

另请参阅 processId (), started (), waitForStarted (),和 setNativeArguments ().

void QProcess:: start (const QString & command , QIODevice::OpenMode mode = ReadWrite)

这是重载函数。

Starts the command command in a new process. The OpenMode is set to mode .

command is a single string of text containing both the program name and its arguments. The arguments are separated by one or more spaces. For example:

QProcess process;
process.start("del /s *.txt");
// same as process.start("del", QStringList() << "/s" << "*.txt");
...
							

Arguments containing spaces must be quoted to be correctly supplied to the new process. For example:

QProcess process;
process.start("dir \"My Documents\"");
							

Literal quotes in the command string are represented by triple quotes. For example:

QProcess process;
process.start("dir \"Epic 12\"\"\" Singles\"");
							

After the command string has been split and unquoted, this function behaves like the overload which takes the arguments as a string list.

You can disable this overload by defining QT_NO_PROCESS_COMBINED_ARGUMENT_START when you compile your applications. This can be useful if you want to ensure that you are not splitting arguments unintentionally, for example. In virtually all cases, using the other overload is the preferred method.

On operating systems where the system API for passing command line arguments to a subprocess natively uses a single string (Windows), one can conceive command lines which cannot be passed via QProcess 's portable list-based API. In these rare cases you need to use setProgram () 和 setNativeArguments () instead of this function.

void QProcess:: start ( QIODevice::OpenMode mode = ReadWrite)

这是重载函数。

Starts the program set by setProgram () with arguments set by setArguments ()。 OpenMode is set to mode .

This function was introduced in Qt 5.1.

另请参阅 open (), setProgram (),和 setArguments ().

bool QProcess:: startDetached ( qint64 * pid = nullptr)

Starts the program set by setProgram () with arguments set by setArguments () in a new process, and detaches from it. Returns true 当成功时;否则返回 false . If the calling process exits, the detached process will continue to run unaffected.

Unix: The started process will run in its own session and act like a daemon.

The process will be started in the directory set by setWorkingDirectory ()。若 workingDirectory () is empty, the working directory is inherited from the calling process.

注意: On QNX, this may cause all application threads to temporarily freeze.

If the function is successful then * pid is set to the process identifier of the started process. Note that the child process may exit and the PID may become invalid without notice. Furthermore, after the child process exits, the same PID may be recycled and used by a completely different process. User code should be careful when using this variable, especially if one intends to forcibly terminate the process by operating system means.

Only the following property setters are supported by startDetached():

All other properties of the QProcess object are ignored.

注意: The called process inherits the console window of the calling process. To suppress console output, redirect standard/error output to QProcess::nullDevice ().

This function was introduced in Qt 5.10.

另请参阅 start (), startDetached (const QString &program, const QStringList &arguments, const QString &workingDirectory, qint64 *pid), and startDetached (const QString &command).

[static] bool QProcess:: startDetached (const QString & program , const QStringList & arguments , const QString & workingDirectory = QString(), qint64 * pid = nullptr)

This function overloads startDetached ().

Starts the program program 采用自变量 arguments in a new process, and detaches from it. Returns true 当成功时;否则返回 false . If the calling process exits, the detached process will continue to run unaffected.

Argument handling is identical to the respective start () overload.

The process will be started in the directory workingDirectory 。若 workingDirectory is empty, the working directory is inherited from the calling process.

If the function is successful then * pid is set to the process identifier of the started process.

另请参阅 start ().

[static] bool QProcess:: startDetached (const QString & command )

This function overloads startDetached ().

Starts the command command in a new process, and detaches from it. Returns true 当成功时;否则返回 false .

Argument handling is identical to the respective start () overload.

After the command string has been split and unquoted, this function behaves like the overload which takes the arguments as a string list.

另请参阅 start (const QString &command, QIODevice::OpenMode mode).

[signal] void QProcess:: started ()

This signal is emitted by QProcess when the process has started, and state () 返回 Running .

注意: 这是私有信号。它可以用于信号连接,但不能由用户发射。

QProcess::ProcessState QProcess:: state () const

Returns the current state of the process.

另请参阅 stateChanged () 和 error ().

[signal] void QProcess:: stateChanged ( QProcess::ProcessState newState )

This signal is emitted whenever the state of QProcess changes. The newState argument is the state QProcess changed to.

注意: 这是私有信号。它可以用于信号连接,但不能由用户发射。

[static] QStringList QProcess:: systemEnvironment ()

Returns the environment of the calling process as a list of key=value pairs. Example:

QStringList environment = QProcess::systemEnvironment();
// environment = {"PATH=/usr/bin:/usr/local/bin",
//                "USER=greg", "HOME=/home/greg"}
							

This function does not cache the system environment. Therefore, it's possible to obtain an updated version of the environment if low-level C library functions like setenv or putenv have been called.

However, note that repeated calls to this function will recreate the list of environment variables, which is a non-trivial operation.

注意: For new code, it is recommended to use QProcessEnvironment::systemEnvironment ()

This function was introduced in Qt 4.1.

另请参阅 QProcessEnvironment::systemEnvironment () 和 setProcessEnvironment ().

[slot] void QProcess:: terminate ()

Attempts to terminate the process.

The process may not exit as a result of calling this function (it is given the chance to prompt the user for any unsaved files, etc).

On Windows, terminate() posts a WM_CLOSE message to all top-level windows of the process and then to the main thread of the process itself. On Unix and macOS the SIGTERM signal is sent.

Console applications on Windows that do not run an event loop, or whose event loop does not handle the WM_CLOSE message, can only be terminated by calling kill ().

另请参阅 kill ().

[override virtual] bool QProcess:: waitForBytesWritten ( int msecs = 30000)

Reimplemented from QIODevice::waitForBytesWritten ().

bool QProcess:: waitForFinished ( int msecs = 30000)

Blocks until the process has finished and the finished () 信号已被发射,或直到 msecs 毫秒已过去。

返回 true if the process finished; otherwise returns false (若操作超时,若发生错误,或者若此 QProcess is already finished).

This function can operate without an event loop. It is useful when writing non-GUI applications and when performing I/O operations in a non-GUI thread.

警告: Calling this function from the main (GUI) thread might cause your user interface to freeze.

若 msecs 为 -1,此函数不会超时。

另请参阅 finished (), waitForStarted (), waitForReadyRead (),和 waitForBytesWritten ().

[override virtual] bool QProcess:: waitForReadyRead ( int msecs = 30000)

Reimplemented from QIODevice::waitForReadyRead ().

bool QProcess:: waitForStarted ( int msecs = 30000)

Blocks until the process has started and the started () 信号已被发射,或直到 msecs 毫秒已过去。

返回 true if the process was started successfully; otherwise returns false (if the operation timed out or if an error occurred).

This function can operate without an event loop. It is useful when writing non-GUI applications and when performing I/O operations in a non-GUI thread.

警告: Calling this function from the main (GUI) thread might cause your user interface to freeze.

若 msecs 为 -1,此函数不会超时。

注意: On some UNIX operating systems, this function may return true but the process may later report a QProcess::FailedToStart error.

另请参阅 started (), waitForReadyRead (), waitForBytesWritten (),和 waitForFinished ().

QString QProcess:: workingDirectory () const

QProcess has been assigned a working directory, this function returns the working directory that the QProcess will enter before the program has started. Otherwise, (i.e., no directory has been assigned,) an empty string is returned, and QProcess will use the application's current working directory instead.

另请参阅 setWorkingDirectory ().

[override virtual protected] qint64 QProcess:: writeData (const char * data , qint64 len )

Reimplemented from QIODevice::writeData ().

相关非成员

typedef Q_PID

Typedef for the identifiers used to represent processes on the underlying platform. On Unix, this corresponds to qint64 ; on Windows, it corresponds to _PROCESS_INFORMATION* .

另请参阅 QProcess::pid ().

宏文档编制

QT_NO_PROCESS_COMBINED_ARGUMENT_START

Disables the QProcess::start () overload taking a single string. In most cases where it is used, the user intends for the first argument to be treated atomically as per the other overload.

This function was introduced in Qt 5.6.

另请参阅 QProcess::start (const QString &command, QIODevice::OpenMode mode).