filefrag [ -bblocksize ] [ -BeksvxX ] [ files... ]
filefrag reports on how badly fragmented a particular file might be. It makes allowances for indirect blocks for ext2 and ext3 filesystems, but can be used on files for any filesystem.
The filefrag program initially attempts to get the extent information using FIEMAP ioctl which is more efficient and faster. If FIEMAP is not supported then filefrag will fall back to using FIBMAP.
filefrag was written by Theodore Ts'o <firstname.lastname@example.org>.