Bash shortcut function to cd you to an ancestor directory, named as first argument. Stop having to cd ../../../..

cdup.sh

#!/bin/bash
# Usage: cdup [DIRNAME]
# Bash shortcut function to cd you to ancestor directory named as first argument. 
# If DIRNAME is not supplied, then .. is used.
# Stop having to cd ../../../..
# Use `cd -` to undo, to restore old working directory. 
# Use aliases for common directories, like: alias docroot="cdup docroot".
# Add function to your ~/.profile
# 
# Example:
# $ pwd
# > /var/www/html/example.com/docroot/long/path/to/something
# $ cdup html
# $ pwd
# > /var/www/html
# $ cd -
# $ pwd
# > /var/www/html/example.com/docroot/long/path/to/something

function cdup {
  if [ $# == 0 ]; then
    cd ..
    return 0
  fi
  
  dir="$1"
  old=`pwd`
  new=`sed s:/$dir/.*:/$dir: <<< $old`
  if [ "$old" == "$new" ]; then
    echo "Can't find '$dir' among ancestor directories." 1>&2
    return 1
  fi
  cd $new
}

FYI: Latest is going to go here: https://github.com/westonruter/misc-cli-tools/blob/master/cdup