This is the Python version of the MD5 test program from the MD5 Internet Draft (Rivest and Dusse, The MD5 Message-Digest Algorithm, 10 July 1991). The file "foo" contains the string "abc" with no trailing newline. When called without arguments, it acts as a filter. When called with "-x", it executes a self-test, and the output should literally match the output given in the RFC. Code by Jan-Hein B\"uhrman after the original in C.
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.