What's a convenient way of checking what's being added to a log file in realtime?

Question

Right now I'm essentially executing tail /var/log/syslog manually every once in a while. Is there something that lets me see what's being added continuously, or do I need to write something myself?

This is often called “tailing”, after tail -f. See also How to have tail -f show colored output and more generally the tail tag. — Gilles 'SO- stop being evil', May 05 '11 at 22:41

score 11 · Accepted Answer · edited May 05 '11 at 22:37

11

I believe you're looking for the -f switch. It will continue to follow the the log file as it changes.

tail -f /var/log/syslog

You can vary the number of lines that are output using the -n switch as well:

tail -f -n 20 /var/log/syslog

See man tail for more information.

edited May 05 '11 at 22:37

cjm

27,160

answered May 05 '11 at 22:08

3

tail -f | grep ... | while read line; do ...; done is an extremely common scripting idiom among sysadmins. (Yes variants of of it using popen() styled subprocesses count as using the same idiom). It's used to selectively process logged events in near real-time (for example to send alerts or initiated automated remediation scripts). – Jim Dennis May 06 '11 at 00:58

What's a convenient way of checking what's being added to a log file in realtime?

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