pyenv-virtualenv-realpath

#!/usr/bin/env bash
# Summary: Substitute realpath if unavailable as a builtin or file
# Usage: . pyenv-virtualenv-realpath

if ! {
    enable -f "${BASH_SOURCE%/*}"/../libexec/pyenv-realpath.dylib realpath ||
      type realpath
  } >/dev/null 2>&1; then
  if [ -n "$PYENV_NATIVE_EXT" ]; then
    echo "pyenv: failed to load \`realpath' builtin" >&2
    exit 1
  fi

  READLINK=$(type -p greadlink readlink | head -1)
  if [ -z "$READLINK" ]; then
    echo "pyenv: cannot find readlink - are you missing GNU coreutils?" >&2
    exit 1
  fi

  resolve_link() {
    $READLINK "$1"
  }

  realpath() {
    local f="$*" \
          name dir
    [[ $f ]] || {
      >&2 echo ${FUNCNAME[0]}: missing operand
      return
    }
    while [[ -L $f ]]; do
      f="$(resolve_link "$f")"
    done
    if [[ ! -d $f ]]; then
      name="/${f##*/}"
      # parent?
      dir="${f%/*}"
      if [[ $dir == $f ]]; then
        #lacks /: parent is current directory
        f="$PWD"
      else
        f="$dir"
      fi
    fi
    #absolute directory
    dir="$(cd "$f"
           pwd)"
    echo "$dir$name"
  }
fi