Can I filter output from `tail` with the `-f` flag?

Question

I'd like to tail -f the output of access_log on RHEL 6.8 but pipe and grep that output to act as a filter. Is there such an option?

That is I'd like live output from:

# tail -f error_log | grep <<ON.THIS.IP.ADDY>>

Currently I'm doing something akin to this, but it's clunky:

watch -n 5 'tail -n 10 access_log | grep <<ON.THIS.IP.ADDY>>'

The terminal would appear to 'hang' after the first command. The accepted answer below was all I needed. Adding `--line-buffered` solved all problems. — Rick, Jul 14 '16 at 18:59

score 3 · Accepted Answer · answered Jul 14 '16 at 16:22

3

I just did a tail -f <nginx-access.log> | grep <ip> and as expected new lines showed up regularly.

What happens when you try? Could it be hat your grep buffers (I think i've seen that), in that case it might help to add --line-buffered to the grep.

answered Jul 14 '16 at 16:22

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Can I filter output from `tail` with the `-f` flag?

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