A not so very useful type of application, just a IO in C practice. The md5 algorithm: http://bradconte.com/md5_c
Takes 2 arguments, descriped below. The checksum is written to file as binary.
-make
-make clean
-add , add md5 checksum to end of file
-test , recompute the checksum and validate it with one attached to the end of the file
-strip , remove the checksum from the file
md5 -add "filename"
md5 -test "filename"
md5 -strip "filename"