taoc

#!/bin/bash
# @Function
# tac lines colorfully. taoc means *CO*lorful c*AT* in reverse(last line first).
#
# @Usage
#   $ echo -e 'Hello\nWorld' | taoc
#   $ taoc /path/to/file1
#   $ taoc /path/to/file1 /path/to/file2
#
# @online-doc https://github.com/oldratlee/useful-scripts/blob/dev-2.x/docs/shell.md#-coat
# @author Jerry Lee (oldratlee at gmail dot com)
set -eEuo pipefail

# if stdout is a terminal, use cat directly.
#   '-t' check: is a terminal?
#   check isatty in bash https://stackoverflow.com/questions/10022323
[ ! -t 1 ] && exec tac "$@"

readonly -a ROTATE_COLORS=(33 35 36 31 32 37 34)
COUNT=0
rotateColorPrint() {
  local content="$*"

  # skip color for white space
  if [[ "$content" =~ ^[[:space:]]*$ ]]; then
    printf '%s\n' "$content"
  else
    local color="${ROTATE_COLORS[COUNT++ % ${#ROTATE_COLORS[@]}]}"
    printf '\e[1;%sm%s\e[0m\n' "$color" "$content"
  fi
}

# Bash read line does not read leading spaces
# https://stackoverflow.com/questions/29689172
tac "$@" | while IFS= read -r line; do
  rotateColorPrint "$line"
done