write（）系统调用何时写入所有请求的缓冲区而不是仅进行部分写入？

If I am counting on my write() system call to write say e.g., 100 bytes, I always put that write() call in a loop that checks to see if the length that gets returned is what I expected to send and, if not, it bumps the buffer pointer and decreases the length by the amount that was written.If I am counting on my write() system call to w