Piping tail output though grep twice

bash shell unix grep tail

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.

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

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

bash shell unix grep tail

This is the result of buffering, it will eventually print when enough data is available.

Use the --line-buffered option as suggested by Shawn Chin or if stdbuf is available you can get the same effect with:

tail -f access_log | stdbuf -oL grep "127.0.0.1" | grep -v ".css"

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