svn commit: r225868 - head/bin/ps

[Jilles Tjoelker]

On Sat, Oct 01, 2011 at 05:14:01PM +0000, Alexander Best wrote:
> On Sat Oct  1 11, Ed Schouten wrote:
> > Also, it would be better if we replaced the "??" string with "-". When
> > we print "??", it actually means: this process has no controlling
> > terminal, not that we don't know which TTY it is.

> good point. also i was thinking: if a process had a controlling
> terminal, but that terminal has been revoked, are users really
> interested to know what the name of that revoked terminal was? can't
> we just use "-"? is it important to know whether a process never had a
> controlling terminal, or had one at some point, but not anymore?

I think this is potentially useful, because it shows that the process
did not explicitly detach from the terminal (such as via setsid(2)).

Particularly if the terminal is real (not a pseudo-terminal), its name
may be useful in recognition.

When asking for processes attached to a specific terminal with ps's t
option, ps will also show processes that used to be attached ("-"),
possibly allowing users to keep track of processes better.

It appears that even if a terminal is "revoked" in this way, it still
prevents reuse of the pts number.

> also the ps(1) man page claims that a process running on console has a "TT"
> entry of "con". i've never seen such an entry. is this still correct?

This may indeed be no longer the case, although it was never common to
see "con". With syscons in multi-user mode, you cannot log in on
/dev/console, only on /dev/ttyv*. With syscons in single-user mode,
ps(1) says "v0" or "ttyv0" but tty(1) says /dev/console.

> and the last point i'd like to make: looking at 'ps alx' on freebsd
> 7.x makes it easy to distinguish between ttys and pts'es, because they
> are names ttyvX and ttypX. looking at the same output under HEAD, all
> pts terminal descriptors have moved to /dev/pts/X. so they will not
> show up as pX, but merely as X.

> can't we tell ps to prefix anything coming from /dev/pts with a "p"?

> in this output:

>  1001 1780 1778   1  16  0   15956   3136 pause    Is    0    0:00,02 /usr/local/bin/zsh

> users are supposed to know that the "0" stands for /dev/pts/0. imho

>  1001 1780 1778   1  16  0   15956   3136 pause    Is   p0    0:00,02 /usr/local/bin/zsh

> would be much better here (like under freebsd 7.x).

I rather like the new output. Pseudo-terminals are by far the most
common kind of terminal and there may be many of them, so it makes sense
not to have a prefix. The t option in ps also accepts these short names,
like 'ps lt0'. All other terminal names start with a letter.

In FreeBSD 7, the first 256 pseudo-terminals are named
/dev/tty[pqrsPQRS][0-9a-v]. A few more letters can be used to provide a
few more pseudo-terminals but even then two characters suffice.

The TTY keyword shows the full pathname relative to /dev.

-- 
Jilles Tjoelker