filenameext/3
filenameext(Filename,MainPart,Ext)
Return or replace a file name's extension
Remarks
The returned strings are in upper case. Note that the dot is considered a part of the extension. If the MainPart is an input argument, its extension - if any - will be ignored (see example below).
Example
filenameext("prolog.exe",Name,Ext),
filenameext(NewName,"prolog.exe",".err").
Name=PROLOG, Ext=.EXE, NewName=PROLOG.ERR