up - Change the shell working directory to a directory in the current working directory context.

up [dir]

Within the context of the current working directory path change the shell working directory
to the first directory name that matches [dir]. The default action if [dir] is not set is
to change the shell working directory up one directory.

Copy and rename up.sh to /usr/bin/up and add a entry to your .bashrc to source the file.
cp up.sh /usr/bin/up
vi ~/.bashrc
    Add the following line to the top of the file and save and quit.
    source /usr/bin/up
source ~/.bashrc

Bash