relative path

[Ray Andrews <rayandrews@eastlink.ca>]

Like anyone, when I'm working on something complicated I make copious 
backups, and if I find I've introduced some bug I run previous versions 
to see where the bug was introduced.   But I often have six terminals 
openat once, with different versions running here and there and it's 
easy to forget which terminal is running which backup, so I do this:

In file 'test' then being backed up to 'test,1' 'test,2' etc:

    function my_function ()
    {
    _vvar=`whence -vS $0 | cut --delimiter=' ' --fields=7-`
    _ooutput=`ls -g --time-style=+%F/%T $_vvar | cut --delimiter=' '
    --fields=5-`
    echo -e "Function: $0 \nFile: $_ooutput"

    # code below:

    }

    $ . ./test; my_function
    Function: my_function
    File: 2018-02-21/13:07:10 ./test

    $ cp test test,2

    $ . ./test,2; my_function
    Function: my_function
    File: 2018-02-21/13:07:20 ./test,2

So, as various copies of the function run I can see the file that was 
sourced and its date, and I know which is newer than which. There's just 
one small problem and that's if I source the files via a relative path 
that path is the one seen by 'whence' and if I run the function out of 
the directory where the file is located, whence still sees the relative 
path but of course 'ls' now can't find the file.   This isn't a big 
problem in practice but I'm curious if there would be a solution.  Some 
way of capturing the absolute path even when I actually use a relative 
path.  I think there is, I have a niggling I've used it but I can't 
remember.