tail -f with highlighting

If you want to highlight something when doing ‘tail -f’ you can use the following command:

tail -f /var/log/logfile | perl -p -e 's/(something)/\033[7;1m$1\033[0m/g;'

or if your terminal supports colours, e.g. linux terminal, you can use this:

tail -f /var/log/logfile | perl -p -e 's/(something)/\033[46;1m$1\033[0m/g;'

If you need to highlight multiple words you can use something like this:

tail -f /var/log/logfile | perl -p -e 's/\b(something|something_else)\b/\033[46;1m$1\033[0m/g;'

and if you want it to beep on a match use this:

tail -f /var/log/logfile | perl -p -e 's/(something)/\033[46;1m$1\033[0m\007/g;'

If you find that perl is too heavy for this you can use sed:

tail -f /var/log/logfile | sed "s/\(something\)/\x1b[46;1m\1\x1b[0m/g"

Note, that in the last example you have to actually type “cntl-v cntl-[” in place of “^[”
\x1b character can also be used as the escape character.

For the full list of control characters on Linux you can look at:

man console_codes