Thread: Querying the hostname of the server

Hi,

I have a number of PostgreSQL servers which I often access through ssh tunnel with Pgadmin3. I would like to double check which one I have landed on (if the tunnel is really configured the way I want). Is there a way to query the hostname from the catalogs?

Thanks

Peter

On Fri, Apr 30, 2010 at 03:33:13PM +0200, Péter Kovács wrote:
> Hi,
>
> I have a number of PostgreSQL servers which I often access through ssh
> tunnel with Pgadmin3. I would like to double check which one I have landed
> on (if the tunnel is really configured the way I want). Is there a way to
> query the hostname from the catalogs?

Hmm, that's a bit tricky, since I assume you're using a local db
connection inside the tunnel, so inet_server_addr() probably returns
null. If you're talking unix/linux machines, then /etc/hostname _should_
have the current hostname in it, so:

create temp table foo (t text);
copy foo from '/etc/hostname';
select * from foo;
drop table foo;

Should work.

Ross
--
Ross Reedstrom, Ph.D.                                 reedstrm@rice.edu
Systems Engineer & Admin, Research Scientist        phone: 713-348-6166
The Connexions Project      http://cnx.org            fax: 713-348-3665
Rice University MS-375, Houston, TX 77005
GPG Key fingerprint = F023 82C8 9B0E 2CC6 0D8E  F888 D3AE 810E 88F0 BEDE

"Ross J. Reedstrom" <reedstrm@rice.edu> wrote:

> If you're talking unix/linux machines, then /etc/hostname _should_
> have the current hostname in it

If not, check for /etc/HOSTNAME -- some distributions do that.

-Kevin

Thank you, Ross!

--- On Fri, 30/4/10, Ross J. Reedstrom <reedstrm@rice.edu> wrote:

> > Hi,
> >
> > I have a number of PostgreSQL servers which I often
> access through ssh
> > tunnel with Pgadmin3. I would like to double check
> which one I have landed
> > on (if the tunnel is really configured the way I
> want). Is there a way to
> > query the hostname from the catalogs?
>
> Hmm, that's a bit tricky, since I assume you're using a
> local db
> connection inside the tunnel, so inet_server_addr()
> probably returns
> null. If you're talking unix/linux machines, then
> /etc/hostname _should_
> have the current hostname in it, so:
>
> create temp table foo (t text);
> copy foo from '/etc/hostname';
> select * from foo;
> drop table foo;
>
> Should work.
>

Or you could do something like:

CREATE OR REPLACE FUNCTION hostname()
RETURNS text AS
$BODY$
    $host = `hostname`;
        return $host;
$BODY$
LANGUAGE 'plperlu';

Yes, nice and simple.

I just did this in C and it works ok!

hostname.c
===========================================

#include <unistd.h>
#include "postgres.h"
#include "utils/elog.h"
#include "utils/palloc.h"
#include "storage/bufpage.h"
#define MAX_HOST_SIZE   200

PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(hostname);
Datum hostname(PG_FUNCTION_ARGS);

Datum
hostname(PG_FUNCTION_ARGS)
{
        int len;
        char buf[MAX_HOST_SIZE + 1];
        text *result;

        gethostname(buf,MAX_HOST_SIZE);
        len = strlen(buf);
        //elog(NOTICE, "hostname=%s\n",buf);
        result=(text *)palloc(len + VARHDRSZ);
        SET_VARSIZE(result, len + VARHDRSZ);
        memcpy(VARDATA(result),buf,strlen(buf));
        PG_RETURN_POINTER(result);
}


Makefile
===========================================
MODULE_big = hostname
OBJS = hostname.o

ifdef USE_PGXS
PG_CONFIG = pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)
include $(PGXS)
else
subdir = /var/lib/pgsql/src/Ccode/hostname
top_builddir = /usr/local/src/postgresql-8.3.3
include $(top_builddir)/src/Makefile.global
include $(top_srcdir)/contrib/contrib-global.mk
endif


hostname.sql
==================================================
CREATE OR REPLACE FUNCTION hostname() RETURNS text
    AS '$libdir/hostname', 'hostname'
    LANGUAGE c IMMUTABLE STRICT;


Στις Friday 30 April 2010 17:43:49 ο/η Glyn Astill έγραψε:
> --- On Fri, 30/4/10, Ross J. Reedstrom <reedstrm@rice.edu> wrote:
>
> > > Hi,
> > >
> > > I have a number of PostgreSQL servers which I often
> > access through ssh
> > > tunnel with Pgadmin3. I would like to double check
> > which one I have landed
> > > on (if the tunnel is really configured the way I
> > want). Is there a way to
> > > query the hostname from the catalogs?
> >
> > Hmm, that's a bit tricky, since I assume you're using a
> > local db
> > connection inside the tunnel, so inet_server_addr()
> > probably returns
> > null. If you're talking unix/linux machines, then
> > /etc/hostname _should_
> > have the current hostname in it, so:
> >
> > create temp table foo (t text);
> > copy foo from '/etc/hostname';
> > select * from foo;
> > drop table foo;
> >
> > Should work.
> >
>
> Or you could do something like:
>
> CREATE OR REPLACE FUNCTION hostname()
> RETURNS text AS
> $BODY$
>     $host = `hostname`;
>         return $host;
> $BODY$
> LANGUAGE 'plperlu';
>
>
>
>
>
>



--
Achilleas Mantzios

I think you can do something like that as a postgresql user

su - postgres
 
psql -c "\! uname -n"

or actually you can do that inside of any sql statement

psql
\!uname -n




> Date: Fri, 30 Apr 2010 09:14:04 -0500
> From: reedstrm@rice.edu
> To: pgsql-admin@postgresql.org
> Subject: Re: [ADMIN] Querying the hostname of the server
>
> On Fri, Apr 30, 2010 at 03:33:13PM +0200, Péter Kovács wrote:
> > Hi,
> >
> > I have a number of PostgreSQL servers which I often access through ssh
> > tunnel with Pgadmin3. I would like to double check which one I have landed
> > on (if the tunnel is really configured the way I want). Is there a way to
> > query the hostname from the catalogs?
>
> Hmm, that's a bit tricky, since I assume you're using a local db
> connection inside the tunnel, so inet_server_addr() probably returns
> null. If you're talking unix/linux machines, then /etc/hostname _should_
> have the current hostname in it, so:
>
> create temp table foo (t text);
> copy foo from '/etc/hostname';
> select * from foo;
> drop table foo;
>
> Should work.
>
> Ross
> --
> Ross Reedstrom, Ph.D. reedstrm@rice.edu
> Systems Engineer & Admin, Research Scientist phone: 713-348-6166
> The Connexions Project http://cnx.org fax: 713-348-3665
> Rice University MS-375, Houston, TX 77005
> GPG Key fingerprint = F023 82C8 9B0E 2CC6 0D8E F888 D3AE 810E 88F0 BEDE
>
> --
> Sent via pgsql-admin mailing list (pgsql-admin@postgresql.org)
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