rp

#!/usr/bin/env bash
# @Function
# convert to Relative Path.
#
# @Usage
#   # if 1 argument, print relative path to current dir.
#   $ ./rp /etc/apache2/httpd.conf
#   # if more than 1 argument, print relative path to last argument.
#   $ ./rp a.txt ../b.txt /etc/passwd /etc/apache2
#
# @online-doc https://github.com/oldratlee/useful-scripts/blob/dev-3.x/docs/shell.md#-ap-and-rp
# @author Jerry Lee (oldratlee at gmail dot com)
set -eEuo pipefail

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

################################################################################
# util functions
################################################################################

redPrint() {
  # if stdout is a terminal, turn on color output.
  #   '-t' check: is a terminal?
  #   check isatty in bash https://stackoverflow.com/questions/10022323
  if [ -t 1 ]; then
    printf '\e[1;31m%s\e[0m\n' "$*"
  else
    printf '%s\n' "$*"
  fi
}

die() {
  local prompt_help=false exit_status=2
  while (($# > 0)); do
    case "$1" in
    -h)
      prompt_help=true
      shift
      ;;
    -s)
      exit_status=$2
      shift 2
      ;;
    *)
      break
      ;;
    esac
  done

  (($# > 0)) && redPrint "$PROG: $*"
  $prompt_help && echo "Try '$PROG --help' for more information."

  exit "$exit_status"
} >&2

portableRelPath() {
  local file=$1 relTo=$2 uname

  uname=$(uname)
  case "$uname" in
  Linux* | CYGWIN* | MINGW*)
    realpath "$f" --relative-to="$relTo"
    ;;
  Darwin*)
    local py_args=(-c 'import os, sys; print(os.path.relpath(sys.argv[1], sys.argv[2]))' "$file" "$relTo")
    if type -P grealpath >/dev/null; then
      grealpath "$f" --relative-to="$relTo"
    elif type -P python3 >/dev/null; then
      python3 "${py_args[@]}"
    elif type -P python >/dev/null; then
      python "${py_args[@]}"
    else
      die "fail to find command(grealpath/python3/python) to get relative path!"
    fi
    ;;
  *)
    die "uname($uname) NOT support!"
    ;;
  esac
}

usage() {
  cat <<EOF
Usage: $PROG [OPTION]... [FILE]...
convert to Relative Path.

Example:
  $PROG path    # relative to current dir
  $PROG path1 relativeToPath
  $PROG */*.c relativeToPath

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
}

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

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

((${#files[@]} == 0)) && die -h "requires at least one argument!"

if ((${#files[@]} == 1)); then
  relativeTo=.
else
  argc=${#files[@]}

  # Get last argument
  relativeTo=${files[argc - 1]}
  files=("${files[@]:0:argc-1}")
fi

[ -f "$relativeTo" ] && relativeTo=$(dirname -- "$relativeTo")
[ -e "$relativeTo" ] || die "relativeTo dir($relativeTo): No such file or directory!"

readonly files relativeTo

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

has_error=false

for f in "${files[@]}"; do
  if [ -e "$f" ]; then
    portableRelPath "$f" "$relativeTo"
  else
    redPrint "$PROG: $f: No such file or directory!" >&2
    has_error=true
  fi
done

# set exit status
! $has_error