我相信这里的问题是，第一个是grep的缓冲，这意味着第二个grep的将不会看到它，直到缓冲区将刷新输出。

I believe the problem here is that the first grep is buffering the output which means the second grep won't see it until the buffer is flushed.

尝试添加 - 行缓冲选项你的第一个grep的：

Try adding the --line-buffered option on your first grep:

tail -f access_log | grep --line-buffered "127.0.0.1" | grep -v ".css"

有关更多信息，请参见的BashFAQ / 009 - 什么是缓冲或者说，为什么我的命令行中不产生输出：尾-f日志文件| grep的'富巴| awk的... 的

For more info, see "BashFAQ/009 -- What is buffering? Or, why does my command line produce no output: tail -f logfile | grep 'foo bar' | awk ..."