How do you colorize only some keywords for a bash script?

supercat seems to do what you're looking for.

Package: supercat
Description-en: program that colorizes text for terminals and HTML
 Supercat is a program that colorizes text based on matching regular
 expressions/strings/characters. Supercat supports html output as well
 as standard ASCII text. Unlike some text-colorizing programs that
 exist, Supercat does not require you to have to be a programmer to
 make colorization rules.
Homepage: http://supercat.nosredna.net/

There doesn't seem to be any way to tell it what to colourise on the command line, you have to specify a config file.

I seem to recall there used to be a program called 'hilite' or 'hl' that highlighted text that matched a pattern (like grep --colour, but displaying non-matching lines too), but I couldn't find it when I searched for it.

Finally, GNU grep can be used to highlight patterns - but only one colour can be used (i.e. you can't have PASS in green and FAIL in red, both would be highlighted with the same colour).

Pipe your data through something like this:

egrep --color "\b(PASS|FAIL)\b|$"

This example uses egrep (aka grep -E), but -G basic regexp, -F fixed-string, and -P PCRE also work.

All matches will be highlighted. Default is red, or set the GREP_COLOR env var.

The key to this working is that the final |$ in the pattern matches end-of-line (i.e. all lines match) so all lines will be displayed (but not colorised).

The \b are word-boundary markers so that it matches e.g. FAIL but not FAILURE. they're not necessary, so remove them if you want to match partial words.

Here's the example wrapper script for supercat that I wrote yesterday. It works, but in writing it, I discovered that supercat doesn't have any option for case-insensitive searches. IMO, that makes the program significantly less useful. It did, however, greatly simplify the script because I didn't have to write a '-i' option :)

#! /bin/bash 

# Requires: tempfile from debian-utils, getopt from util-linux, and supercat

SCRIPTNAME=$(basename $0)
CFGFILE=$(tempfile -p spc)

usage() {
  cat <<__EOF__
Highlight regexp patterns found on stdin or files specified on command
line with specified colours.

Usage: $SCRIPTNAME [ --colour "pattern" ...] [FILE]

Options:

        -k,--black   regexp
        -r,--red     regexp
        -g,--green   regexp
        -y,--yellow  regexp
        -b,--blue    regexp
        -m,--magenta regexp
        -c,--cyan    regexp
        -w,--white   regexp

Example:

    run-script.sh | $SCRIPTNAME --green PASS --red FAIL

__EOF__
  exit 0
}


# Format definition from the spc man page:
#1234567890123456789012345678901234567890123456789012345
#HTML Color Name      Col A N T RE / String / Characters
FMT="%-20s %3s %1s %1s %1s (%s)\n"

add_color_to_config() {
  COLOR="$1"
  PATTERN="$2"

  printf "$FMT" "$COLOR" "$COLOR" - 0 r "$PATTERN" >> "$CFGFILE"
}


# uses the "getopt" program from util-linux, which supports long
# options. The "getopts" built-in to bash does not.
TEMP=$(getopt \
       -o 'hk:r:g:y:b:m:c:w:' \
       -l 'help,black:,red:,green:,yellow:,blue:,magenta:,cyan:,white:' \
       -n "$0" -- "$@")

if [ $? != 0 ] ; then echo "Terminating..." >&2 ; exit 1 ; fi

eval set -- "$TEMP"

while true ; do
    case "$1" in
        -k|--bla*)       add_color_to_config blk "$2" ; shift 2 ;;
        -r|--red)        add_color_to_config red "$2" ; shift 2 ;;
        -g|--gre*)       add_color_to_config grn "$2" ; shift 2 ;;
        -y|--yel*)       add_color_to_config yel "$2" ; shift 2 ;;
        -b|--blu*)       add_color_to_config blu "$2" ; shift 2 ;;
        -m|--mag*)       add_color_to_config mag "$2" ; shift 2 ;;
        -c|--cya*)       add_color_to_config cya "$2" ; shift 2 ;;
        -w|--whi*)       add_color_to_config whi "$2" ; shift 2 ;;

        -h|--hel*)       usage ; exit 0 ;;

        --)         shift ; break ;;

        *)          echo 'Unknown option!' ; exit 1 ;;
    esac
done

spc -R -c "$CFGFILE" "$@"
rm -f "$CFGFILE"

Here is a general-purpose script to colorize regex patterns (probably needs some retouching):

#! /bin/bash

color_to_num () {
  case $1 in
    black)  echo 0;;
    red)    echo 1;;
    green)  echo 2;;
    yellow) echo 3;;
    blue)   echo 4;;
    purple) echo 5;;
    cyan)   echo 6;;
    white)  echo 7;;
    *)      echo 0;;
  esac
}

# default values for foreground and background colors
bg=
fg=
bold="$(tput bold)"
italics=""
boundary=""

while getopts f:b:sli option; do
  case "$option" in
    f) fg="$OPTARG";;
    b) bg="$OPTARG";;
    s) bold="";;
    l) boundary=".*";;
    i) italics="$(tput sitm)";;
  esac
done

shift $(($OPTIND - 1))

pattern="$*"

if [ -n "$fg" ]; then
  fg=$(tput setaf $(color_to_num $fg))
fi
if [ -n "$bg" ]; then
  bg=$(tput setab $(color_to_num $bg))
fi

if [ -z "$fg$bg" ]; then
  fg=$(tput smso)
fi

sed "s/${boundary}${pattern}${boundary}/${bold}${italics}${fg}${bg}&$(tput sgr0)/g"

Name it hilite.sh and use it this way:

$ ./BIN_PROGRAM | hilite.sh -f green PASS | hilite.sh -f red FAIL

$ # Here is an example one liner
$ echo -e "line 1: PASS\nline 2: FAIL" | hilite.sh -f green PASS | hilite.sh -f red FAIL

Embedding arbitrary strings (like tput output) into sed replace expressions is problematic because you have to ensure (by escaping) the string is valid sed syntax, which is more complexity that is best avoided. I would use awk instead. Just as an example:

{ echo line 1: PASS; echo line 2: FAIL; } | 
    awk -v "red=$(tput setaf 1)" -v "green=$(tput setaf 2)" \
        -v "reset=$(tput sgr0)" '
    { for (i = 1; i <= NF; i++) {
           if ($i == "FAIL") printf "%s", red "FAIL" reset;
           else if ($i == "PASS") printf "%s", green "PASS" reset;
           else printf "%s", $i

           if (i == NF) printf "%s", ORS
           else printf "%s", OFS 
      }}'

The key is to assign the tput sequences to awk variables, done here using the -v options.