1Once upon a time Upas ran on many versions of Unix. 2This is a partial rewrite to ANSI C specifically for Plan 9. 3It uses's Plan 9's bio library instead of stdio and Plan 9's 4regular expression library. 5 6I've tried to make portability possible but it has 7never been ported. To port Upas to another system: 8 9 - port Plan 9's libbio library working on that system (already available). 10 - port Plan 9's regexp library working on that system (should just compile). 11 - rewrite common/libsys.c to reflect system calls for that system. This 12 file contains all the really system dependent code that differs between 13 Plan 9 and each Unix. This includes file management, signal 14 handling, process control and error handling. 15 - change the important directory trees in common/mail.c to reflect 16 where you want things like 17 - get the ARGBEGIN/ARGEND/ARGF macros from Plan 9's libc.h 18 - get the include files correct in common/sys.h 19 - rewrite smtp/mxdial to use the conventions of that system 20 - rewrite runq.c to walk queues on that system. 21