I am trying to get \"abc.txt\" out of /this/is/could/be/any/path/abc.txt using Unix command.
Note that /this/is/could/be/any/path is d
basename path gives the file name at the end of path
Edit:
It is probably worth adding that a common pattern is to use back quotes around commands e.g. `basename ...`, so UNIX shells will execute the command and return its textual value.
So to assign the result of basename to a variable, use
x=`basename ...path...`
and $x will be the file name.