There exists in GameMaker: Studio a number of functions that enable you to manipulate files in different ways:
The following functions can be used to change file names:
Note: These functions do not work on the actual files! They only deal with the strings.
Finally there are two special functions for getting filenames
that can be used for loading and saving files with file-type
Note: These functions are Windows ONLY.
WARNING! These functions may not work as you expect due to GameMaker: Studio being sandboxed! Please see the section on File System Limits for more information.