Which is all the more reason to use existing well-tested tools as much as possible - the less code one needs to write to achieve a task, the lower the chance of bugs creeping in.

If you run ShellCheck against the script it will highlight "Double quote to prevent globbing and word splitting." - whilst this is only listed as "info" (because ShellCheck doesn't know what variables contain) any time a variable contains a filename, it is a bug in the script, because certain filenames will cause errors.

Another example - if your grep still looks what Pan quoted in post #14 then there's probably a bug there, because it's not doing a whole line match. That's also easily fixable, but if you can instead replace the whole while/grep section with something based on either of the commands in post #7 then that's even less code...

I see what you mean now. I do find Linux quite temperamental about file names and paths compared to Windows. I will fix that thank you.

No, it is not true. Windows tries to be much more user-friendly by hiding the complexity of the underlying mechanisms with some built-in features (like automatic handling of "weird" characters like spaces in filenames and paths), which ultimately makes it even more inscrutable.

Whichever way you like to look at it. I just like the fact that I can type cd \program files or cd \Program Files and it will get me there, whereas Linux will not tolerate me typing a path in lower case when I should be typing caps and vice versa. I am a Windows person, so naturally I will find Linux harder to use than Windows - not because one is easier/harder than the other, but more because I am used to how Windows works.

I have run the shellcheck. Really good idea (and I will use that in future). It has shown me where to double quote which I have now fixed. It shows everything else as correct, apart from recommending grep -q and SC2001 to use ${variable//search/replace} instead. I am not fussed about grep -q (as the output is handy) and SC2001 just seems to be another way to do the same thing without sed. I might as well change that as the coding is a lot easier to read than using sed.

Windows is not linux and linux is not windows. https://linux.oneandoneis2.org/LNW.htm
Obviously you are allowed to like (prefer) windows, in that case use windows.

https://github.com/koalaman/shellcheck/issues/1768
this is not just another way to do the same thing, but a more efficient way.