pid              process ID
ppid             parent process ID
pgrp             process group ID
uid              UID of process
gid              GID of process
euid             effective UID
egid             effective GID
suid             saved UID
sgid             saved GID
priority         priority of process
size             size of process in KB (data + stack)
rss              resident set size in KB
flags            process flags (see <sys/proc.h>)
nice             nice for cpu usage
sess             session pointer
time             total cpu time, microseconds
stime            system time, microseconds
utime            user time, microseconds
start            start time of process in seconds since epoch
wchan            address of current system call (though the docs make
                 it look like we can have a name if we hold our tongues
ttydev           device name of tty, or empty if none
ttynum           device number of tty, or -1 if none
pctcpu           (decayed) %cpu for this process
pctmem           %memory for this process
state            state of process
cmndline         entire command line for the process
fname            command name

Note that although time, stime, and utime are returned in microseconds,
the actual resolution appears to be centiseconds.

The comments in the code for ps indicate that the cmndline and fname
values are not to be relied on, since they are modifiable by the
program itself once it begins execution.

I'd like to provide the following attributes, I just can't figure out
sid              session id
majflt           major page faults
minflt           minor page faults

The page fault information actually looks like it might be available,
but it appears not to be. At any rate, the distributed ps doesn't
provide it. The source for ps contains a bunch of conditionalizations
on FIXME, which appears not to be defined. I have dropped them, but it
appears that only if FIXME is defined do you get the page fault
information, and even then not always.

The sess is actually the address of a session structure. I'd love to
extract the sid from this structure, but I segv when I try. I didn't
try too hard, because the ps command also reports session pointer, not
session ID.

I'd like to provide the following attributes, but the Darwin ps
documentation makes me believe they're not available:
exec             absolute filename (including path) of executed command