FreeTDS Development Group

["James K. Lowden" <james.k.lowden AT icloud.com>]

On Fri, 27 Feb 2015 15:14:52 +0100
Marc-André Legrand <legrandmarc20 AT hotmail.com> wrote:

> Server is "192.168.1.32"
> looking up hostname for ip address 192.168.1.32
> osql: warning: no DNS hostname found for "192.168.1.32"
> Usage: host [-aCdlriTwv] [-c class] [-N ndots] [-t type] [-W time]
>             [-R number] [-m flag] hostname [server]
[etc.]
>        -m set memory debugging flag (trace|record|usage)
> osql: no IP address found for ""

There is an odd error in osql that I don't see.  I would run it as

        $ sh -x $(which osql) -S MyMSSQLServerName -U user -P password

to watch for the last assignment to the HOST variable.  The relevant
lines start at line 340:

if [ "${HOST}" = "$(echo ${HOST} | sed 's/[^.0-9]*//')" ]
then 
        ADDRESS=${HOST}
        echo 'looking up hostname for ip address' ${ADDRESS}
        HOST=$(host ${HOST} | awk '/domain/ {print $5}' | sed 's/\.$//')
        if [ -z "${HOST}" ]
        then
                echo "$(basename $0): warning: \
                        no DNS hostname found for \"${ADDRESS}\"" 
                HOST=${ADDRESS} # restore host address string
        fi
fi

In English:

        if host is all numeric characters
                addr = host # save name
                look for hostname of address with host->awk->sed
                if no hostname found (host is "")
                        issue message
                        host = addr # restore name

I don't see how that can fail.  Logically, it seems that 

                if [ -z "${HOST}" ]

evaluates to False even though HOST is in fact a zero-length string.
We know it's numeric going in because we see the message 

        osql: warning: no DNS hostname found for "192.168.1.32"

and zero-length coming out because we see

        osql: no IP address found for ""

Running the script with the -x option should reveal where it goes
wrong.  

BTW, this test might be improved: 

        [ "${HOST}" = "$(echo ${HOST} | sed 's/[^.0-9]*//')" ]

written as 

        [ ${HOST} -a -z ${HOST%%[.0-9]*} ]

The first version tests if HOST is the same after non-digits (and '.')
are removed.  The second tests if HOST comprises only digits and '.'.  

The things you learn....

--jkl