Checking whether postgresql is running

[Possible duplicate: original sent to novice never got through! -;(]
Hi all!
Testing a script where I need to make sure that postgresql is running
before passing a <psql dbasename -c "insert into ..." > instruction I
faced this curious behaviour:

This is the relevant content of the script:
------------------
#!/bin/bash
/usr/lib/postgresql/bin/pg_ctl status -D /var/lib/postgres/data >/dev/null 2>&1
rtn=$?
if [ $rtn -ne 0 ]; then
echo "not running"
else
echo "ok ok"
fi

Now, if I run the script as root, I get:

ok ok

(or, commenting the script if condition:
pg_ctl: postmaster is running (pid: 18658)
Command line was:
/usr/lib/postgresql/bin/postmasteir)

whereas, if I run the same script as ordinary user, the answer is:

not running

(or, commenting the if lines:
pg_ctl: postmaster or postgres is not running)

--------------
Everything is being tested on the same PC [running PG 7.2.1-2Woody5
under GNU/Linux, k. 2.2.22], root being on /dev/tty1, user on
/dev/tty2, and postgresql not being stopped while switching from root
to user :-).
Could anybody throw some light on this issue?
Thanks for your attention,
Ennio.

--
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--
[Perche' usare Win$ozz (dico io) se ..."anche uno sciocco sa farlo. \\?//
Fa' qualche cosa di cui non sei capace!" (diceva Henry Miller) ] (°|°)
[Why to use Win$ozz (I say) if ... "even a fool can do that. )=(
Do something you aren't good at!" (used to say Henry Miller) ]