Symbolic WCHAN for 4.[12] ps.

[ron%brl-vgr at sri-unix.UUCP]

From:      Ron Natalie <ron at brl-vgr>

On both 4.1c and 4.2 BSD we added a third argument to the "sleep"
call that in addition to storing WCHAN and PRI stored a small text
string to indicate what you were waiting on.   PS makes use of this
and we added another magic character to the tty driver (typically
control-T) that types out the status of all the processes on the
current terminal...for example it looks like this right now:

125 (58) WAIT
1989 (58) TTYI
1970 (58) SOCKIO
1971 (58) RUN

First column is PROC number, second number is UID.  125 is my login
shell, 1989 is mail reading from the terminal.  1971 and 1970 are two
processes in the background connected by a pipe.

This is useful to determine what is reading from the terminal or do
make determinations like "it's not in a loop, it's waiting for you
to type something."

-Ron