Random terminal color for grep, silver searcher, etc.

random_color.sh

#!/bin/bash

# Select a random color for search utilities such as 'grep' or 'ag'.
# Create an alias: alias ag='ag --color-match="$(random_color)"'
# Or, alias grep='GREP_COLOR="$(random_color)" grep'
random_color() {
  # List of highlight colors to iterate between
  #   Legacy Terminal color codes,
  #     01;33 - light yellow text
  #     01;34 - dark blue text
  #     01;35 - light pink text
  #     01;36 - light cyan text
  #     33;41 - yellow on red
  #     33;44 - yellow on blue
  #     33;45 - yellow on pink
  #     1;33;46 - yellow on cyan
  #   Modern Terminal color codes,
  #   32;2;(FOREGROUND RGB);48;2;(BACKGROUND RGB)
  #     38;2;255;255;0;48;2;150;150;80 - yellow on mustard
  #     38;2;255;255;255;48;2;100;100;150 - white on blueish gray
  #     38;2;0;0;0;48;2;255;100;150 - black on pink
  #
  declare -r colors=(
    "01;34" # dark blue text
    "38;2;0;0;0;48;2;255;100;150" # black on pink
    "33;44" # yellow on blue
    "38;2;255;255;0;48;2;150;150;80" # yellow on mustard
    "01;35" # light pink text
    "38;2;255;255;255;48;2;100;100;150" # white on blueish gray
  )

  # File to maintain the counter (we can't set an env var).
  declare -r file="${HOME}/.random_color"

  # Read only a numeric value from file.
  value=`cat $file 2> /dev/null`
  counter=$(echo $value | sed 's/[^0-9]*//g')

  # Increment the circular counter.
  incremented=$((1 + $counter))
  index=$(($incremented % ${#colors[@]}))

  # Write back for persistence.
  echo "${index}" > $file

  echo ${colors[$index]}
}