import sys
           import os

           # if it happens to match but it really short, ignore it as
           # its probably not what we want
           IGNORE_LENGTH=10

           # these variables contain paths that would make little
           # sense to abbreviate to (except HOME, where we just want
           # to deal with it nicer)
           IGNORE_VARS=["PWD", "HOME", "OLDPWD"]

           # in order to still show home as ~ and /home/user as ~user
           # we need to have some special logic.  If you wanted a dir
           # /foobar to show up as the dir %, then you could add an
           # entry for that here.
           SPECIAL_REPLACEMENTS=[["/home/" + os.environ["USER"], "~"],
                                 ["/home/", "~"]]

           # we want to sort a pair of lists by the lengths of their
           # first elements, so we need a comparator function
           def longest_a_first_comp(x,y):
               return len(y[0])-len(x[0])

           in_path = sys.argv[1] if sys.argv[1:] else ""

           # get all the environment variables, reversed in mapping so
           # we can do reverse variable expansion. Or is it
           # variable condension?  variable condensation?
           env = [[v,k] for k,v in os.environ.items()]

           # sort them by length.  This is so if we have:
           #    $FOO_SRC="/home/user/src/foo"
           #    $SRCS="/home/user/src"
           # we will take the longer one.  I think this is always what
           # a user wants.
           env.sort(longest_a_first_comp)

           for r in env:
               # the substitution only happens if it would shorten the path
               if in_path.startswith(r[0]) \
                      and r[1] not in IGNORE_VARS\
                      and len(r[0]) > IGNORE_LENGTH\
                      and len(r[1]) < len(r[0]):
                   # prefix with a dollar sign so it looks like an
                   # environment variable.  The dollar sign needs to
                   # be escaped, and it's escape needs to be escaped.
                   print "\\$" + in_path.replace(r[0], r[1], 1)
                   sys.exit(0)

           for r in SPECIAL_REPLACEMENTS:
               if in_path.startswith(r[0]):
                   print in_path.replace(r[0], r[1], 1)
                   sys.exit(0)

           # if we didn't do any condensations, yield the original path
           print in_path
     

           PS1="\u@\h \w $ "
           promptFunc() {
               PS1="${COLOR_GREEN_BOLD}\u@\h"
               PS1="${PS1}${COLOR_BLUE_BOLD}"
               PS1="${PS1}$(python ~/bin/fix_path.py $(pwd)) $"
           }

           if [ $(whoami) == "myusername" ]
           then
               PROMPT_COMMAND=promptFunc
           else
               # so if someone does an "su" at my terminal its really obvious
               unset PROMPT_COMMAND
           fi