Write a Bash script called mymv $($which replaces the GNU utility mv$)$ that tries to rename the specified file $($using the GNU utility mv$),$ but if the destination file exists, instead creates an index number to append to the destination file, a sort of version number. So if I type:

$ mymv a$.$txt b$.$txt

but b$.$txt already exists, mymv will move the file to b$.$txt$\mathrm{.}1.$ Note that if b$.$txt$\mathrm{.}1$ already exists, you must rename the file to b$.$txt$\mathrm{.}2,$ and so on$,$ until you can successfully rename the file to a name that does not already exist.