topic Re: rval of nslookup in Operating System - HP-UX

rval of nslookup

Kevin Wright — Fri, 03 Aug 2001 16:58:35 GMT

does anyone know why nslookup is always returning a return value of 0, whether it works or not?

nslookup host
rval=$?
if [[ $rval -eq 0 ]];then
echo 'it works'
else
echo 'no host'
fi

this always returns 'it works' no matter what host yo put in??

I use the rval with grep all the time, and 0 is success, 1 is fail. can this not be done with nslookup?

Re: rval of nslookup

James R. Ferguson — Fri, 03 Aug 2001 17:08:17 GMT

Hi Kevin:

There's no rule that you must exit with a zero/non-zero value. Convention dictates that zero (0) is success and (1) is failure. Two (2) is often used to denote a "warning". However, as a writer I could just as easily exit(0), regardless.

...JRF...

Re: rval of nslookup

Victor BERRIDGE — Fri, 03 Aug 2001 17:10:04 GMT

Hi,
Well I would say the command succeeded although it did not find what you were looking for (the command did work) so why not test on something like "can't find host" ?

My 2 cents

ALl the best
Victor

Re: rval of nslookup

Joseph C. Denman — Fri, 03 Aug 2001 17:14:16 GMT

Victor is correct. The command did succeed. Just because it did not find anything does not cause failure. FTP works the same way. It always ends in rval 0.

...jcd...

Re: rval of nslookup

Bill Hassell — Fri, 03 Aug 2001 17:19:50 GMT

nslookup has many different functions and the rules it follows determine whether it produces the result you are looking for. For instance, nslookup may be told to look in /etc/hosts first and does not find the hostname so it asks the DNSD server and finds it. Is that a failure, a success or half a failure?

nslookup is one of many ways to resolve an address. A better way for your question is the little known command: getip

Re: rval of nslookup

A. Clay Stephenson — Fri, 03 Aug 2001 17:19:51 GMT

Hi Kevin:

Welcome to UNIX, just because the rules and conventions are there doesn't mean the developer has to follow them. Sometimes you have to do string patterm matching (and this is one of them); sometimes you have to look at the 3rd column of the 10th line of output to
know it a command succeeded.

If you really want to be frustrated try using remsh.

Regards, Clay

Re: rval of nslookup

Kevin Wright — Fri, 03 Aug 2001 17:33:06 GMT

I get it now, pretty stupid huh, the command worked fine, therefore the exit of 0, just because it did not find a host does not mean the command failed..
thanks, you know someone could really learn alot from you guys.

Re: rval of nslookup

Magdi KAMAL — Mon, 06 Aug 2001 10:40:37 GMT

Hi Kevin,

I would say, all hp-ux commands which got internal menus ( like lanadmin, ftp, nslookup, rgy_edit, ...) have the same behaviour like what you discribe : Return exit 0 upon completion whether succeeded or not ( that's mean finshes with succes but don't mean the what it was doing is succeeded ! ).

But usual hp-ux commands ( not divisible commands ) behave like what you supposed initially. If a command no not succeed what it is intended to do so the return code will be different from 0.

Magdi