a2l

#!/usr/bin/env bash
# @Function
# print each arguments on one line colorfully.
#
# @Usage
#   $ ./a2l arg1 arg2
#   $ ./a2l *.txt
#
# @online-doc https://github.com/oldratlee/useful-scripts/blob/dev-3.x/docs/shell.md#-a2l
# @author Jerry Lee (oldratlee at gmail dot com)
set -eEuo pipefail

readonly PROG=${0##*/}
readonly PROG_VERSION='3.x-dev'

################################################################################
# parse options
################################################################################

usage() {
  cat <<EOF
Usage: $PROG [OPTION]... ARG...
print each arguments on one line colorfully.

Example:
  $PROG arg1 arg2
  $PROG */*.py

Options:
  -h, --help      display this help and exit
  -V, --version   display version information and exit
EOF

  exit
}

progVersion() {
  printf '%s\n' "$PROG $PROG_VERSION"
  exit
}

args=()
while (($# > 0)); do
  case "$1" in
  -h | --help)
    usage
    ;;
  -V | --version)
    progVersion
    ;;
  --)
    shift
    args=(${args[@]:+"${args[@]}"} "$@")
    break
    ;;
  -*)
    # if unrecognized option, treat it and all follow arguments as args
    args=(${args[@]:+"${args[@]}"} "$@")
    break
    ;;
  *)
    # if not option, treat it and all follow arguments as args
    args=(${args[@]:+"${args[@]}"} "$@")
    break
    ;;
  esac
done
readonly args

################################################################################
# biz logic
################################################################################

readonly -a ROTATE_COLORS=(33 35 36 31 32 37 34)
COLOR_INDEX=0
rotateColorPrint() {
  local content=$*
  # - if stdout is a terminal, turn on color output.
  #   '-t' check: is a terminal?
  #   check isatty in bash https://stackoverflow.com/questions/10022323
  # - skip color for white space
  if [[ ! -t 1 || $content =~ ^[[:space:]]*$ ]]; then
    printf '%s\n' "$content"
  else
    local color=${ROTATE_COLORS[COLOR_INDEX++ % ${#ROTATE_COLORS[@]}]}
    printf '\e[1;%sm%s\e[0m\n' "$color" "$content"
  fi
}

for a in ${args[@]:+"${args[@]}"}; do
  rotateColorPrint "$a"
done