所需的数据被从读取缓冲区拷贝到用户缓冲区，read调用返回。

The requested amount of data is copied from the read buffer into the user buffer, and the read call returns.

youdao

所需的数据被从读取缓冲区拷贝到用户缓冲区，read()调用返回。

Step two: data is copied from the kernel buffer into the user buffer, and the read system call returns.

youdao

所需的数据被从读取缓冲区拷贝到用户缓冲区，read()调用返回。

Step two: data is copied from the kernel buffer into the user buffer, and the read system call returns.

youdao