在Qt中启动并写入终端 [英] Launch and write to terminal in Qt

问题描述

我正在使用Qt在Linux中进行编码.我了解使用popen或QProcess可以从程序启动终端，但是如何写入呢?我在周围的人周围google都在建议fork()和pipe(). 我的目的是使用终端执行ICMP ping，并在ping成功后停止.我用popen做到了，但是我无法停止ping进程，因此我的程序无法运行.

I am coding in linux using Qt. I understand that with popen or QProcess I can launch terminal from my program, but how do I write into to it? I google around people are suggesting fork() and pipe(). My purpose is to do an ICMP ping with the terminal, and stop when ping successfully. I made it with popen, but I couldn't stop the ping process thus my program won't run.

推荐答案

您没有向终端写任何东西，因为没有终端.您传递要运行的程序的名称及其参数作为 QProcess::start 方法.如果您只需要知道ping是否成功，就足以检查您先前使用QProcess::start启动的进程的退出代码；您不必读取其输出.

You don't write anything to terminal because there's no terminal. You pass name of a program to run and its arguments as arguments of the QProcess::start method. If you only need to know if ping was successful or not it's enough to check the exit code of the process which you started earlier using QProcess::start; you don't have to read its output.

来自 ping(8)-Linux手册页

如果ping没有收到任何答复 数据包将全部退出，并带有代码 1.如果同时指定了数据包计数和截止日期，并且少于计数 数据包在 截止日期到了，它也会 以代码1退出.出现其他错误时，退出 以代码2退出.否则退出 代码为0.这样就可以 使用退出代码查看主机是否为 是否活着.

If ping does not receive any reply packets at all it will exit with code 1. If a packet count and deadline are both specified, and fewer than count packets are received by the time the deadline has arrived, it will also exit with code 1. On other error it exits with code 2. Otherwise it exits with code 0. This makes it possible to use the exit code to see if a host is alive or not.

默认情况下，Linux下的ping会运行，直到将其停止为止.但是，您可以使用-c X选项仅发送X个数据包，并使用-w X选项将整个过程的超时设置为X秒.这样，您可以限制ping的运行时间.
以下是使用QProcess在Windows上运行ping程序的工作示例.对于Linux，您必须相应地更改ping选项(例如，将-n更改为-c).在此示例中，ping最多运行X次，其中X是您赋予Ping类构造函数的选项.一旦这些执行中的任何一个以退出代码0返回(表示成功)，就会发出值为true的result信号.如果没有成功执行，则发出result信号，其值为false.

By default ping under Linux runs until you stop it. You can however use -c X option to send only X packets and -w X option to set timeout of the whole process to X seconds. This way you can limit the time ping will take to run.
Below is a working example of using QProcess to run ping program on Windows. For Linux you have to change ping options accordingly (for example -n to -c). In the example, ping is run up to X times, where X is the option you give to Ping class constructor. As soon as any of these executions returns with exit code 0 (meaning success) the result signal is emitted with value true. If no execution is successful the result signal is emitted with value false.

#include <QCoreApplication>
#include <QObject>
#include <QProcess>
#include <QTimer>
#include <QDebug>


class Ping : public QObject {

    Q_OBJECT

public:

    Ping(int count)
    : QObject(), count_(count) {

        arguments_ << "-n" << "1" << "example.com";

        QObject::connect(&process_,
                         SIGNAL(finished(int, QProcess::ExitStatus)),
                         this,
                         SLOT(handlePingOutput(int, QProcess::ExitStatus)));
    };

public slots:

    void handlePingOutput(int exitCode, QProcess::ExitStatus exitStatus) {
        qDebug() << exitCode;
        qDebug() << exitStatus;
        qDebug() << static_cast<QIODevice*>(QObject::sender())->readAll();
        if (!exitCode) {
            emit result(true);
        } else {
            if (--count_) {
                QTimer::singleShot(1000, this, SLOT(ping()));
            } else {
                emit result(false);
            }
        }
    }

    void ping() {
        process_.start("ping", arguments_);
    }

signals:

    void result(bool res);

private:

    QProcess process_;
    QStringList arguments_;
    int count_;
};


class Test : public QObject {

    Q_OBJECT

public:
    Test() : QObject() {};

public slots:
    void handle(bool result) {
        if (result)
            qDebug() << "Ping suceeded";
        else
            qDebug() << "Ping failed";
    }
};


int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);

    Test test;
    Ping ping(3);
    QObject::connect(&ping,
                     SIGNAL(result(bool)),
                     &test,
                     SLOT(handle(bool)));

    ping.ping();
    app.exec();
}

#include "main.moc"

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