I want is to cat a log file and highlight certain lines with color based on a pattern match but to ignore case. For example:

  • When the log file has the word success then make that line green.
  • When it finds error make that line red etc.

This is what I have so far. It is based on cat and awk (although when I used man awk I got man for gawk instead). I am using Debian Jessie.


[ $# -ge 1 -a -f "$1" ] && logfile="$1" || logfile="-"
cat $logfile | awk '
/install/ {print "\033[32m" $0 "\033[39m"}
/success/ {print "\033[32m" $0 "\033[39m"}
/status/ {print "\033[33m" $0 "\033[39m"}
/info/ {print "\033[33m" $0 "\033[39m"}
/error/ {print "\033[31m" $0 "\033[39m"}
/fail/ {print "\033[31m" $0 "\033[39m"}

I have used all manner of stuff, but I end up with all my text in 1 colour, no colour, or the case is not being ignored. Things like IGNORECASE=1 don't seem to work.

I am happy to use something else, as I just pinched this script from another question. Below is exactly what I want in case someone wants to suggest a new script.

  1. use a command followed by a filename and print the contents to the terminal (using bash would be ideal)
  2. in my script I would like to add strings to match and make those lines in a log/text file a certain color when printed to the screen. eg. find the word error and make that line red
  3. ignore case for the words I want to match, eg. find the word error, ERROR, or any combination of upper lower case, like Error, or ERRor etc. Then print that line to the screen in a red color.

The idea is to be able to easily spot important parts in some of my backup, and things like apache access logs or whatever. I intend to find the important key words I am after and then simply adding those in my script.

Below is a snippet of the beginning and end of one of log files as an example:

INFO: tar attempt number 0
SUCCESS: website tar exists.
INFO: DB backup dump, attempt number 0
SUCCESS: DB backup file created.
INFO: CN Website and DB backed up on Thu.2015-04-30.
  • Can you share a snippet of your logfile also ?
    – amisax
    Jul 15, 2015 at 4:05
  • I've added an example to the end of my question. I was intending to check out a few logs like apache access logs, ssh logs etc and define a few key words I want to have coloured. So ultimately I wanted to use this against all kinds of log files.
    – dakka
    Jul 15, 2015 at 4:52

1 Answer 1


Awk has a function called 'tolower':

cat $logfile | awk '
     tolower($0) ~ /install/ {print "\033[32m" $0 "\033[39m"; next;}
     tolower($0) ~ /success/ {print "\033[32m" $0 "\033[39m"; next;}
     tolower($0) ~ /status/ {print "\033[33m" $0 "\033[39m";  next;}
     tolower($0) ~ /info/ {print "\033[33m" $0 "\033[39m";    next;}
     tolower($0) ~ /error/ {print "\033[31m" $0 "\033[39m";   next;}
     tolower($0) ~ /fail/ {print "\033[31m" $0 "\033[39m";    next;}
     { print; }

With Bash, you can use shopt -s nocasematch for case insensitive pattern matching. eg.

shopt -s nocasematch
if [[ ${mystring} == abcdefg ]] ; then
     echo "is a match!!"
  • Almost! That displays only what I am matching, is there a way to match everything else without changing the colours? I want the log to print out normally like when you use cat filename except what my script matches should be in different colours...hope that made sense?
    – dakka
    Jul 15, 2015 at 4:46
  • @dakka - I've updated the answer.
    – user14755
    Jul 15, 2015 at 4:53

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