Changelog:
1.22.1:
Ed now departs from POSIX and ignores SIGPIPE to prevent commands like
'w !:' or ',!:' from terminating ed. A broken pipe is now detected as any
other write error. (Reported by Sergei Trofimovich).
1.22.0:
An ex(1) style filter has been implemented; the shell escape command
(!) now accepts line addresses to filter the addressed lines through a shell
command. (Suggested by Shawn Wagner, Andrew L. Moore, and John Cowan).