QProcess::close() 是否在进程上引发 unix SIGTERM 信号? [英] Does QProcess::close() raise the unix SIGTERM signal on the process?
问题描述
在 Linux/Qt 中,我有一个 GUI 应用程序.GUI 使用 QProcess 启动其他子进程.要关闭子进程,我使用 QProcess::close().
In Linux/Qt I have a GUI application. The GUI starts up additional child processes using QProcess. To close the child processes I use QProcess::close().
是否QProcess::close() 为子进程提高unix SIGTERM信号?
Does QProcess::close() raise the unix SIGTERM signal for the child process?
(我已链接到 QProcess 和 close() 的 Qt 文档,因为我无法从文档中判断是否引发了 unix 信号...)
(I have linked to the Qt documentation for QProcess and close() because I can not tell from the documentation if a unix signal is raised...)
更新:更改问题以询问特定的 Unix 信号:SIGTERM.
UPDATE: changed question to ask about a specific unix signal: SIGTERM.
推荐答案
今天我发现 QProcess::close() 不会引发 SIGTERM 信号.为了调试这个问题,我正在捕获子进程的 stderr 和 stdout.剧透:QProcess::terminate() 确实引发了 SIGTERM 信号.
Today I found out that QProcess::close() does not raise the SIGTERM signal. To debug this issue I am capturing the stderr and stdout of the child process. Spoiler: QProcess::terminate() does raise the SIGTERM signal.
处理unix SIGTERM信号的子进程代码:
Child process code to handle unix SIGTERM signal:
static void unixSignalHandler(int signum) {
qDebug("DBG: main.cpp::unixSignalHandler(). signal = %s\n", strsignal(signum));
/*
* Make sure your Qt application gracefully quits.
* NOTE - purpose for calling qApp->exit(0):
* 1. Forces the Qt framework's "main event loop `qApp->exec()`" to quit looping.
* 2. Also emits the QCoreApplication::aboutToQuit() signal. This signal is used for cleanup code.
*/
qApp->exit(0);
}
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
MAINOBJECT mainobject;
/*
* Setup UNIX signal handlers for some of the common signals.
* NOTE common signals:
* SIGINT: The user started the process on the command line and user ctrl-C.
* SIGTERM: The user kills the process using the `kill` command.
* OR
* The process is started using QProcess and SIGTERM is
* issued when QProcess::close() is used to close the process.
*/
if (signal(SIGINT, unixSignalHandler) == SIG_ERR) {
qFatal("ERR - %s(%d): An error occurred while setting a signal handler.\n", __FILE__,__LINE__);
}
if (signal(SIGTERM, unixSignalHandler) == SIG_ERR) {
qFatal("ERR - %s(%d): An error occurred while setting a signal handler.\n", __FILE__,__LINE__);
}
// executes mainbobject.cleanupSlot() when the Qt framework emits aboutToQuit() signal.
QObject::connect(qApp, SIGNAL(aboutToQuit()),
&mainobject, SLOT(cleanupSlot()));
return a.exec();
}
处理子进程的 close() 或 terminate() 的父进程代码:
Parent process code that handles close() or terminate() of the child:
if(this->childProcess1!=NULL && this->childProcess1->state()==QProcess::Running) {
this->childProcess1->terminate(); // raise unix SIGTERM signal on the process (let's it execute cleanup code)
if(childProcess1->waitForFinished() == false) {
qDebug("DBG - MainWindow::close(): Failed to close childProcess1.");
qDebug() << "DBG - childProcess1->exitCode =" << childProcess1->exitCode();
qDebug() << "DBG - childProcess1->ExitStatus =" << childProcess1->exitStatus();
qDebug() << "DBG - childProcess1->error() =" << childProcess1->error();
qDebug() << "DBG - childProcess1->errorString()=" << childProcess1->errorString();
}
}
if(this->childProcess2!=NULL && this->childProcess2->state()== QProcess::Running) {
this->childProcess2->terminate(); // raise unix SIGTERM signal on the process (let's it execute cleanup code)
if(childProcess2->waitForFinished() == false) {
qDebug("DBG - MainWindow::close(): Failed to close childProcess2.");
qDebug() << "DBG - childProcess2->exitCode =" << childProcess2->exitCode();
qDebug() << "DBG - childProcess2->ExitStatus =" << childProcess2->exitStatus();
qDebug() << "DBG - childProcess2->error() =" << childProcess2->error();
qDebug() << "DBG - childProcess2->errorString()=" << childProcess2->errorString();
}
}
当父进程使用QProcess::terminate()
时,子进程输出为:
When the parent uses QProcess::terminate()
, the child process output is:
"DBG: main.cpp::unixSignalHandler(). signal = Terminated
当父进程使用`QProcess::close()时,子进程输出为:
When the parent uses `QProcess::close(), the child process output is:
DBG - PARENTOBJECT::close(): Failed to close childProcess.
DBG - childProcess->exitCode = 0
DBG - childProcess->ExitStatus = 1
DBG - childProcess->error() = 1
DBG - childProcess->errorString()= "Unknown error"
terminate()
实验的输出证明子进程正在收到一个 SIGTERM 信号.
The output from the terminate()
experiment proves that the child process is getting a SIGTERM signal.
close()
实验的输出证明子进程没有收到 SIGTERM 信号.
The output from the close()
experiment proves that the child process is not getting the SIGTERM signal.
如果要向子进程发送 SIGTERM 信号,请使用 QProcess::terminate().
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