is_relative_filename - Returns TRUE if the filename is relative. Allegro game programming library.

       Returns TRUE if the filename is relative or FALSE if it is absolute. Note that an absolute filename under
       DOS  (with  a  device  separator) will be considered as relative under Unix, because there absolute paths
       always start with a slash.

       is_relative_filename - Returns TRUE if the filename is relative. Allegro game programming library.

make_absolute_filename(3alleg4), make_relative_filename(3alleg4)

Allegro                                           version 4.4.3                    is_relative_filename(3alleg4)

#include<allegro.h>intis_relative_filename(constchar*filename);