Color regex matches - without dropping misses

Question

When using grep --color=always I can get pretty color highlighting for regex matches.

However, grep only returns lines with at least one match.

Answer 1

I recently made something similar as a filter. I use it to color the "headers" in a tail with multiple files, like this:

tail -f access.log error.log foo.log | logcol.sh

The headers look like this:

==> access.log <==

I got confused by the quick changes between the different logfiles, so this logcol.sh helps. The ==> is hardcoded for the specific usage but could be a parameter as well.

#!/bin/sh
while read line
do
  if test `expr "$line" : "==>.*"`  -eq 0 ;
  then
    printf '\033[0m%s\n' "$line"
  else
    printf '\033[0;31m%s\n' "$line"
  fi
done

Maybe not the most elegant but I think it's quite readable. I hope I don't have any typos ;-) HTH, rob