How to use a variable in a POSIX Path with AppleScript?

Question

I've been trying for a little while to swap out one of the parts in a POSIX Path with a variable but I've had no success. This is the script I'm trying to develop:

tell application "Finder"
    duplicate POSIX file "/Users/**Variable**/Documents/img.jpg" to POSIX file "/Users/**Variable**/Desktop/" with replacing
end tell

The parts in the path are the places where I want the variable to be present. How can I do this?

Answer 1

You break the string with ampersands & and the variable.

Also, it's good practice to convert posix paths to Mac standard colon: paths prior to scripting Finder. Finder's duplicate function has been buggy since 10.9 in these ways. I have broken out some of the coercions so you can see what's going on.

-- define file and user names
set fileName to "img.jpg"
set user1 to "Mitc"
set user2 to "Mitc"

-- create posix path strings
set path1 to "/Users/" & user1 & "/Documents/" & fileName
set path2 to "/Users/" & user2 & "/Desktop/"

-- convert posix paths into colon paths
set ref1 to (POSIX file path1) as string
set ref2 to (POSIX file path2) as string

-- display dialog ref1 & return & ref2 -- to test
tell application "Finder" to duplicate alias ref1 to alias ref2 with replacing