cd-traverse

#!/bin/bash
# Ancestor/descendant traversal | Spencer Tipping
# Licensed under the terms of the MIT source code license

cd_on '^\.\.[^/]'    cd_traverse_ancestor
cd_on '^\.\.[0-9]+$' cd_traverse_ancestor_n
cd_on '^\*\*'        cd_traverse_descendant

function cd_traverse_ancestor_n {
  local n=${1#..}
  local p=$(yes ../ | head -n $n | tr -d '\n')
  test -n $p && cd_goto $p
}

function cd_traverse_ancestor {
  local pattern="${1#..}[^/]*$"
  local target=$PWD

  while test "$PWD" != / ; do
    builtin cd ..
    if [[ "${PWD##*/}" =~ $pattern ]] ; then
      target=$PWD
      break
    fi
  done
  cd_goto "$target"

  if test $OLDPWD = / ; then
    echo "cd: no ancestor matches '${1#..}'"
    return 1
  fi
}

function cd_traverse_descendant {
  local pattern="${1#\*\*}"
  local depth=1
  local dirs dir

  while : ; do
    dirs="$(find -mindepth $depth -maxdepth $depth -type d 2>/dev/null)"

    if test -z "$dirs" ; then
      echo "cd: no descendant matches '${pattern}'"
      return 1
    fi

    while read dir ; do
      if [[ "$dir" =~ $pattern ]] ; then
        cd_goto "$dir"
        return
      fi
    done <<< "$dirs"

    depth=$((depth + 1))
  done
}