Tail -f + grep?

linux bash unix grep tail
Sten Kin picture Sten Kin · Apr 30, 2014 · Viewed 48.6k times · Source

Tail has the following options: 

-f      The -f option causes tail to not stop when end of file is reached, but rather to wait for additional data to be appended to the
             input.  The -f option is ignored if the standard input is a pipe, but not if it is a FIFO.

I'd like to only grep for something in the tail output. 

tail -f <FILE> | grep <SOMETHING>

Issue is it only run grep once and is done. No other output happens. How can I make grep run correctly with the -f?

Answer

Sunny Patel picture Sunny Patel · Apr 30, 2014

You will find another SO Question helpful: How to 'grep' a continuous stream?

Turn on grep's line buffering mode.

tail -f file | grep --line-buffered my_pattern

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