if(!isLink)什么意思

这是一个条件语句，判断变量 isLink 是否为 false。如果 isLink 为 false，则执行 if 语句块中的代码，否则跳过 if 语句块。具体的代码实现可能会有所不同，但大致的语法格式应该是这样的：

if (!isLink) {
  // 执行代码块
}

其中 ! 是逻辑非运算符，用于取反一个布尔值。因此，如果 isLink 为 false，!isLink 为 true，if 语句块中的代码将会被执行。

相关问题

void client::iniClient() { int times = 5; while(times){ if(!clientSocket){ clientSocket = new QTcpSocket(); connect(clientSocket, SIGNAL(readyRead()), this, SLOT(recData())); connect(clientSocket,SIGNAL(disconnected()),this,SLOT(disconnect())); } if(!isLink){ this->clientSocket->connectToHost(ip,port); if(this->clientSocket->waitForConnected(30000)){ qDebug() << "[QT网络通信]连接服务端成功！"; in.setDevice(clientSocket); isLink = true; return ; }else{ qDebug() << "[QT网络通信]连接服务端失败,重新连接中！"; } } times --; } qDebug() << "[QT网络通信]5次尝试连接服务端失败，请检查服务端是否开启"; }

这是一个 QT 网络通信的客户端初始化函数，主要功能是尝试连接服务端。首先判断是否已经存在客户端套接字 clientSocket，如果不存在则新建一个，并且连接 readyRead 信号和 disconnected 信号到相应的槽函数上。然后判断是否已经连接到服务端，如果没有连接，则尝试连接。如果连接成功，则设置 in 设备为 clientSocket，并将 isLink 标志位设置为 true，然后函数返回。如果连接失败，则输出连接失败的提示信息，并继续尝试连接，最多尝试 5 次。如果尝试 5 次后仍然连接失败，则输出连接失败的提示信息，并且函数返回。

undefined reference to `S_ISLINK'

This error message typically occurs when trying to compile a program that uses the S_ISLINK macro, which is used to check if a file is a symbolic link.

The error is indicating that the linker is unable to find a definition for S_ISLINK, which suggests that the necessary library or header files are not being included in the compilation process.

To fix this issue, you may need to include the appropriate header files and/or link against the necessary libraries. This will depend on the specific programming language and environment you are using.

For example, if you are programming in C, you may need to include the sys/stat.h header file and link against the libc library.

If you are using a build system such as Make, you may need to update the relevant configuration files to ensure that the necessary dependencies are included in the build process.