Very Computer

> The command (dig) that I want to use in a script could:
> 1 successfully return results
> 2 successfully fail to return results because no results are available
> 3 fail altogether due to network problems / unavailability of remote
servers
> etc

> I presume 1 + 2 are stout and 3 is sterr    - can BASH pickup this
> difference?

> Thanks,

> Edward.

> Background:

> I'm planing a script that will use the dig command to check where a domain
> name is delegated to.

> for $domain from a list of domains, I'll run the command:
> dig $domain NS.    (checks what DNS servers a domain is delegated to)

> If the command fails (sterr) I'll write the domain to a failure file
> If the command runs successfully, I'll grep the output for our DNS servers
> and, if found, write $domain to a file localDNS.
> If our DNS servers are not found in the grep I'll write $domain to a file
> remoteDNS.
> For a domains in remoteDNS, I'll establish the actual DNS server from the
> output of the dig command and specify it as a variable $dnsserver.
> $dnsserver will be used in further DNS commands of the form:

> the results will be written to the remoteDNS file.

> etc etc

> so I could dig $domain NS > tmp 2> failure

> tmp would then only contain the standard output of the dig(?) and I could
> then grep tmp for the name servers. Tmp would be written over on each loop
> (could I say on each iteration?)

> > The command (dig) that I want to use in a script could:
> > 1 successfully return results
> > 2 successfully fail to return results because no results are available
> > 3 fail altogether due to network problems / unavailability of remote
> servers
> > etc

> > I presume 1 + 2 are stout and 3 is sterr    - can BASH pickup this
> > difference?

> > Thanks,

> > Edward.

> > Background:

> > I'm planing a script that will use the dig command to check where a domain
> > name is delegated to.

> > for $domain from a list of domains, I'll run the command:
> > dig $domain NS.    (checks what DNS servers a domain is delegated to)

> > If the command fails (sterr) I'll write the domain to a failure file
> > If the command runs successfully, I'll grep the output for our DNS servers
> > and, if found, write $domain to a file localDNS.
> > If our DNS servers are not found in the grep I'll write $domain to a file
> > remoteDNS.
> > For a domains in remoteDNS, I'll establish the actual DNS server from the
> > output of the dig command and specify it as a variable $dnsserver.
> > $dnsserver will be used in further DNS commands of the form:

> > the results will be written to the remoteDNS file.

> > etc etc

> > I've just read about file descriptors
> > you can direct standard outout (1) with >
> > you can direct standard error (2) with 2>

> > so I could dig $domain NS > tmp 2> failure

> > tmp would then only contain the standard output of the dig(?) and I
could
> > then grep tmp for the name servers. Tmp would be written over on each
loop
> > (could I say on each iteration?)

> If you don't want to overwrite tmp or failure with each iteration, use:
> >> tmp
> 2>> failure

> This will append the message to the file rather than overwriting it.

> Also, you can detect the success or failure of a command:

> command && echo SUCCESS || echo failed
> or:
> if command
> then
>     echo SUCCESS
> else
>     echo failed
> fi

> For your script, you could try this for starters:

> info=`dig $domain NS || echo $domain >> failure`
> if [ -n $info ]
> then
>    ## dig succeeded with output
>    ## do your grep here
> else
>    ## dig succeeded with no output
>    echo $domain >> remoteDNS
> fi

> > > Is there a way to differentiate between the output resulting from an
error
> > > generated by a command and the successful completion of a command
(both
> > > normally written to the terminal)  I've heard about sterr and stout
and
> > > think they are both written to the terminal.

> > > The command (dig) that I want to use in a script could:
> > > 1 successfully return results
> > > 2 successfully fail to return results because no results are available
> > > 3 fail altogether due to network problems / unavailability of remote
> > servers
> > > etc

> > > I presume 1 + 2 are stout and 3 is sterr    - can BASH pickup this
> > > difference?

> > > Thanks,

> > > Edward.

> > > Background:

> > > I'm planing a script that will use the dig command to check where a
domain
> > > name is delegated to.

> > > for $domain from a list of domains, I'll run the command:
> > > dig $domain NS.    (checks what DNS servers a domain is delegated to)

> > > If the command fails (sterr) I'll write the domain to a failure file
> > > If the command runs successfully, I'll grep the output for our DNS
servers
> > > and, if found, write $domain to a file localDNS.
> > > If our DNS servers are not found in the grep I'll write $domain to a
file
> > > remoteDNS.
> > > For a domains in remoteDNS, I'll establish the actual DNS server from
the
> > > output of the dig command and specify it as a variable $dnsserver.
> > > $dnsserver will be used in further DNS commands of the form:

> > > the results will be written to the remoteDNS file.

> > > etc etc

> --
>     Chris F.A. Johnson                        http://cfaj.freeshell.org
>     ===================================================================
>     My code (if any) in this post is copyright 2001, Chris F.A. Johnson
>     and may be copied under the terms of the GNU General Public License