Command: ed
Argument: file

Edit the file 'file'. For documentations about how to use 'ed', look
at /doc/build.

You can leave 'ed' with the command 'q', or 'Q' if the file has been
modified.

When in 'ed', the prompr will change to ':'.

The file will be searched for in the current directory. 'ed castle.c' will
edit the castle of the wizard.

A wizard can only edit files in his home directory, and files in /log.

See also w/ls, w/cat