Create a directory.
nonzero on success, zero on error. Specifics of the error can be gleaned from PHYSFS_getLastError.
So if you've got the write dir set to "C:\mygame\writedir" and call PHYSFS_mkdir("downloads/maps") then the directories "C:\mygame\writedir\downloads" and "C:\mygame\writedir\downloads\maps" will be created if possible. If the creation of "maps" fails after we have successfully created "downloads", then the function leaves the created directory behind and reports failure.
Fs Class | Tao.PhysFs Namespace