How can I view log files in Linux and apply custom filters while viewing?

Question

I need to read through some gigantic log files on a Linux system. There\'s a lot of clutter in the logs. At the moment I\'m doing something like this:

cat logf         


        

Answer 1

Based on ghostdog74's answer and the less manpage, I came up with this:

~/.bashrc:

export LESSOPEN='|~/less-filter.sh %s'
export LESS=-R  # to allow ANSI colors

---

~/less-filter.sh:

#!/bin/sh
case "$1" in
*logfile*.log*) ~/less-filter.sed < $1
  ;;
esac

---

~/less-filter.sed:

/deleteLinesLikeThis/d  # to filter out lines
s/this/that/  # to change text on lines (useful to colorize using ANSI escapes)

---

Then:

• less logfileFooBar.log.1 -- applies the filter applies automatically.
• cat logfileFooBar.log.1 | less -- to see the log without filtering

This is adequate for now but I would still like to be able to edit the filters on the fly.