AppleScript: The Definitive Guide, 2nd Edition

File and Alias

A file object is a reference to a file or folder on disk. To construct one, use an object string specifier —the word file followed by a string representing a colon-delimited pathname:

file "feathers:Users:mattneub:"

By "colon-delimited" I mean an old-style Macintosh -type path. This is not the same as the new-style Unix-type path (new to Mac users, anyway), also known as a POSIX path. AppleScript has a long history on Macintosh, so it is not surprising that its native representation of file paths is not the Unix representation. Macintosh paths start with a disk name, and the delimiter between the disk name, folder names, and filename is a colon. A pathname ending in a colon is a folder or a disk. (A partial pathname, one whose first element is not a disk, is taken to start inside the "current directory," but the interpretation of this notion is unreliable, and partial pathnames should be avoided.)

Oddly, you can't assign a file object specifier to a variable, or return it as a value. If you try, you get a runtime error message:

set x to file "feathers:Users:mattneub:"
-- error: Can't make file "feathers:Users:mattneub:" into type reference

Instead, you must generate a reference to the file object, like this:

set x to a reference to file "feathers:Users:mattneub:"
x -- file "feathers:Users:mattneub:" of «script»

A file specifier is not resolved until the script actually runs. This means that the item on disk need not exist at compile time. At runtime, however, when the file ...