bsum

bsum is a tiny tool (256 bytes!) that computes the BSD checksum of any file. It requires only a few kilobytes of memory, and is fast even on an 8086-class PC. bsum supports files of any size (as long as your file system is able to handle them). The BSD checksum is displayed in hexadecimal format (ie. four alphanumeric characters, like "C2E1"). bsum is an excellent candidate for veryfing data integrity on systems that are very constrained in terms of disk space, memory or CPU power. Typically, bsum can be used to verify that files transferred by unreliable means arrived intact.