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Full Discussion: I need help with...<various>
Top Forums Shell Programming and Scripting I need help with...<various> Post 302228245 by era on Saturday 23rd of August 2008 04:24:02 PM
Old 08-23-2008
So you don't care at all about what the nameservers are? Or you want to query all the authoritative name servers in turn? In the former case, host -t a example.com is all you need. In the latter case, what you have (sort of) makes sense, except your version of the script fails to specify which name server to use (but obviously you know how to use dig @server to do that, or you can use host example.com b.iana-servers.net to specify b.i-s.n as the name server to use; but dig is certainly more scripter-friendly).

Code:
#!/bin/sh
host=$1
dig +short ns $host |
while read nameserver; do
  dig +short @$nameserver $host | sed "s/^/IP for $host at $nameserver is /"
done

It's not a one-liner unless your lines have fractal dimensions but I hope that wasn't strictly a requirement.

Last edited by era; 08-23-2008 at 05:37 PM.. Reason: Note absence of @server param; add code snippet
 
SHELL-QUOTE(1p) 					User Contributed Perl Documentation					   SHELL-QUOTE(1p)

NAME
shell-quote - quote arguments for safe use, unmodified in a shell command SYNOPSIS
shell-quote [switch]... arg... DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands or files with embedded white space or shell globbing characters safely. Here are a few examples. EXAMPLES
ssh preserving args When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and passes them to "$SHELL -c". This doesn't work as intended: ssh host touch 'hi there' # fails It creates 2 files, hi and there. Instead, do this: cmd=`shell-quote touch 'hi there'` ssh host "$cmd" This gives you just 1 file, hi there. process find output It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote: eval set -- `find -type f -print0 | xargs -0 shell-quote --` debug shell scripts shell-quote is better than echo for debugging shell scripts. debug() { [ -z "$debug" ] || shell-quote "debug:" "$@" } With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can. save a command for later shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are things the user can't pass through), you can do something like this: user_switches= while [ $# != 0 ] do case x$1 in x--pass-through) [ $# -gt 1 ] || die "need an argument for $1" user_switches="$user_switches "`shell-quote -- "$2"` shift;; # process other switches esac shift done # later eval "shell-quote some-command $user_switches my args" OPTIONS
--debug Turn debugging on. --help Show the usage message and die. --version Show the version number and exit. AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions. AUTHOR
Roderick Schertler <roderick@argon.org> perl v5.8.4 2005-05-03 SHELL-QUOTE(1p)
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