What's a good linux command line utility for watching a log file live? It's probably obvious but I totally forgot it.
4 Answers
There are two things that leap immediately to mind...
tail -f
or
multitail
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thank you sir. I'll give ya the answer since Linker3000 has so many points, but I still appreciate the help! Commented Jan 6, 2011 at 1:25
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also less -F /path to log (i.e. less -F /var/log/messages) Commented Apr 16, 2015 at 11:30
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I like
multitail
- besides specifying multiple file parameters you can view several logs at a time with a wildcard (iemultitail myapp.*.log
) Commented May 3 at 16:48
If you want to watch a specific aspect of your file, say just IPs in an access log, you can do :
tail -f your_file | cut -d' ' -f1 | logtop
assuming that IPs are the first column of your log file.
The tailf
command is functionally equivalent to tail -f
but better in terms of performance. From man tailf
:
tailf will print out the last 10 lines of a file and then wait for the file to grow. It is similar to tail -f but does not access the file when it is not growing. This has the side effect of not updating the access time for the file, so a filesystem flush does not occur periodically when no log activity is happening. tailf is extremely useful for monitoring log files on a laptop when logging is infrequent and the user desires that the hard disk spin down to conserve battery life.