@ALTNAME[filename] : Returns the alternate (short, "8.3" FAT-format) name for the specified file. If the filename is already in 8.3 format, returns the filename. If the file does not exist, returns an empty string. If filename contains a \, @ALTNAME returns the SFN of the full path.
Examples:
echo %@altname["Long Name.exe"]
LONGNA~1.EXE
echo %@altname["C:\Program Files\Microsoft Office"]
C:\PROGRA~1\MICROS~4
echo %@altname["%CommonProgramFiles"]
C:\PROGRA~1\COMMON~1