#!/bin/dash -vx

trim() {
  # remove leading whitespace characters
  __trim="${*#${*%%[![:space:]]*}}"
  # remove trailing whitespace characters
  printf "%s" "${__trim%${__trim##*[![:space:]]}}"
}

trim " alpha" | od -t x1a
trim "beta " | od -t x1a
trim "
gamma	" | od -t x1a

trim2() {
  # remove leading whitespace characters
  __trim="${*##[[:space:]]}"
  # remove trailing whitespace characters
  printf "%s" "${__trim%%[[:space:]]}"
}

trim2 " alpha" | od -t x1a
trim2 "beta " | od -t x1a
trim2 "
gamma	" | od -t x1a

trim3() {
  _space="$(echo -n '[\b\t\n\v\f\r ]')"
  # remove leading whitespace characters
  __trim="${*##$_space}"
  # remove trailing whitespace characters
  printf "%s" "${__trim%%$_space}"
}

trim3 " alpha" | od -t x1a
trim3 "beta " | od -t x1a
trim3 "
gamma	" | od -t x1a