EINTR

linux中函数的返回状态，在不同的函数中意义不同：

1）write

表示：由于信号中断，没写成功任何数据。

The call was interrupted by a signal before any data was written.

2）read

表示：由于信号中断，没读到任何数据。

The call was interrupted by a signal before any data was read.

3）sem_wait

函数调用被信号处理函数中断

The call was interrupted by a signal handler.

4）recv

由于信号中断返回，没有任何数据可用。

function was interrupted by a signal that was caught, before any data was available.