There aren't many character based apps left, but if you still have one, you might like Peek
Peek, by Computronics, is
a user monitoring/control tool for character based applications.
Most Unix platforms are supported, including Linux and SCO
Unlike some of its competitors, Peek doesn't modify the kernel;
it instead relies upon the users running the "pksh" so that running
/etc/peek can work. There's a couple of ways to do that; you can
either just add a call to pksh to the end of their .profiles, or
you can modify their login shell to use pksh- but not exactly as
you might think: obviously you don't really want them running pksh,
you want them running sh, or ksh, or csh, or maybe their shell
isn't a shell at all but brings them straight into an application.
Peek arranges for that by links to /usr/bin/pksh. The install
creates symbolic links for pksh-csh,
pksh-ksh and pksh-sh, but you can add any
link you like, the trick being that your actual application is what
follows the "-". When pksh runs, it looks at the name it was called
with, and strips out what you really want by looking after the "-",
and then it executes that. So if you have changed a user to use
/usr/bin/pksh-ksh, they'll end up running ksh, but pksh will be in
Once that is true, you can use /etc/peek to view that users
character screen. You can also "poke" commands through that will be
executed by that users session. The control interface is very
simple, has built in help, and none of it adds very much CPU
Computronics has done a thorough job of covering all the
problems that come up from using this approach. You are not, for
example, required to be running the same terminal type as monitored
users, but if you are, you can specify that control code sequencs
be executed rather than just shown as printable translations. Or,
you can convert sequences into the appropriate sequences for the
terminal you are using- of course this is slower, may not work at
all for some sequences (just because your terminal may not support
a capability the other terminal has) and is limited to just a
handful of terminal types; still it is a useful feature.
The only problems I had at all with using the same terminal
types was when I entered local peek commands. I had a session on
tty04 that I monitored from tty03, and ran "scoadmin" on tty04.
This displayed perfectly on tty03 (when using the "no translate"
option which tells peek that your terminal types are the same), but
if I triggered any local peek command, I could not recover the
screen even with "Ctrl-L" (which is supposed to redraw it).
However, once I used tty04 to do something which caused the screen
to redraw, the peek on tty03 was once again perfect.
Another potential problem is the use of pseudo ttys. For any
number of reasons, you may need to know (in scripts) what the
"real" device is. The pksh makes that available in the variable
_ttyname. You might also have a problem with the normal dynamic
assignment of pseudo ttys, but Peek allows you to map specific ttys
to specific pseudo ttys just by creating a the /etc/peek_pty_list
file. That would contain lines like this:
This would force the assignment of specific pseudo ttys to
Pseudo ttys take the form "/dev/pts001" (some OS's are
different) and are normally assigned sequentially: the first person
to ask for one gets 001, etc. This can cause problems with
applications that expect that /dev/pts001 is always a wyse60
terminal, or will always be user "jane". Applications that work
this way seldom have any real reason for doing so; it's usually
just dumb programming that causes it, but sometimes you have to
live with it.
Peek also has a buffer which can be as large as 16K. That buffer
lets you see what happened on the users screen before you
ran /etc/peek. It's best feature, however, is when peek is used in
combination with tee and the "peek_replay" command is then used to
examine the captured file. Lets's pretend that the user on tty04
has called me with because they've just had a problem with their
application. It's not something we can duplicate, but I need to see
exactly what happened. Here's what I'd do:
Start peek using tee to save the output:
/etc/peek -nt | tee /tmp/problem.log
Buffer Peek Program
Peek_sco5, 1.09j2 (k) Copyright (c) 1999 Computronics.
User to monitor: tony
Several users are logged in under that name:
1. tony 1144 /dev/tty04
2. tony 1181 /dev/tty05
After choosing the user, I'd immediately exit peek, and then
The peek_replay program recognizes an environment variable
PEEK_BREAK (if you are using an ansi terminal you don't need to set
it). This variable contains the characters you want peek_replay to
pause at, normally anything that re-displays the screen. For ansi,
it's set to "\e[H:\e1;1H", which are the "home cursor" sequences
for ansi. This feature lets you replay the users screens step by
step to see exactly what happened. As you can set up a background
recording, this also is a great way to audit, especially since the
"user" to monitor can be specified by tty device. Let's say, for
example, that you don't completely trust your external support
personnel (hardly an unusual situation, unfortunately). However,
you need to let them dial in for regular maintenance and the like.
You set things up so that their login will run pksh (or so that all
logins do so). If you want, the file /etc/peek_devices can be
created with only the modem lines you want to monitor, or you can
leave that alone. Next , you set up a /etc/peek_on_me script (any
name can be used) that contains
/etc/peek -u $_ttyname -comi > /tmp/peeklog &
And then finally in their .profile, add:
sh >/dev/null 2>&1 /etc/peek_on_me
When they log in, the /etc/peek_on_me script is started, and
their session is recorded in /tmp/peeklog. You'd later use the
peek_replay to run through the /tmp/peeklog and review exactly what
they did (if you were monitoring multiple logins, you'd want to
make /tmp/peeklog unique by adding on a user-name, timestamp or
You can also use peek_replay in the immediate mode: a command
like this is very useful:
/etc/peek -nt -u user -pipe | /etc/peek_replay
That runs you through the current buffer of the user, which
would be ideal in the support scenario proposed above (-pipe wasn't
mentioned in the manual I had, but the tech support folks pointed
it out to me).
In addition to poking commands while actively monitoring a user,
you can send commands from a script using the -cpl_poke option:
echo "lc" | /etc/peek -u mary -cpl_poke
If you needed to grab the results in a script, use the -pipe
option as shown above.
Peek works by periodic polling, which means it could miss
characters at high baud rates or when the user is telnetted in on a
local lan. I observed no such problems in my testing, but it is
possible to change the sample rate if this is an issue. Doing so
will increase the CPU overhead of peek.
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