Trying to change the name of 1 file

Question

I have searched the topic and have not found a solution that works for me,
I am trying to write an AppleScript that will change the name of a single file from path:old.txt to path:new.txt
I have tried
tell application "Finder"
set name of file "work.txt" to PartA & PartG & ticker & ".txt"
end tell
among others and always either receive an error message, access denied or unable to set old file name to new file name

Answer 1

You're missing the point.
set name of file "work.txt" to PartA & PartG & ticker & ".txt"
When you set the name of the file, the Finder needs two things - the original file that you're trying to rename, and the new name you want it to take.
In your revised script you're specifying the existing name (not path) of the file you want to change, and specifying its path along with the new name. That's the wrong way around.
Think of this command in the following manner:
set name of (original file specification) to (new file name)
Now, in the case of the 'original file specification' you need to provide enough information for the Finder to identify the file. You're just saying 'work.txt', but that is not enough (and that's why it's complaining). There could be a hundred 'work.txt' files spread around in different directories on your disk. How is the Finder supposed to know which one you want to change?
A better format would be:
tell application "Finder"
  set name of (file "work.txt" of path to desktop) to "ABC.txt"
end tell
In this way the Finder can absolutely identify which file you want to change (the file 'work.txt' that's on your desktop) and the new name you want it to take.
Now, if the file is not on your desktop you can amend the script to include the relevant path, e.g.:
tell application "Finder"
  set name of (file "work.txt" of folder "blah" of disk "disk name") to "ABC.txt"
end tell
This tells the Finder to look in the folder 'blah' on the specified disk.
You can also do this by including the path to the file in the form:
tell application "Finder"
  set name of (file "disk name:blah:work.txt) to "ABC.txt"
end tell
where you use : to delimit each folder in the path.
Hope that helps.