Shell Programming and Scripting

Hey guys, i am fairly new to scripting and I am trying to write a script that takes a comma delimited file as input. I am trying to figure out a way to determine if $1 and $3 exist on a line (basically a hostname and ip address) and if true do the following,
resolve the hostname to ip.

sample file looks like this:

Code:

hostname.blah.blah.com,blah,10.x.x.x

I am able to awk the file and separate the hostnames and ip's using the following

Code:

cat $filename | awk -F "," '{print $1}'
cat $filename | awk -F "," '{print $3}' | grep '^[0-9]*\.[0-9]*\.[0-9]*\.[\
0-9]*$')

But I am trying to to do this in 1 line, and I'm not sure of the proper syntax and determine whether they both exist on the same line, and if true do the next step.

Thanks in advance.

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---------- Post updated at 05:34 PM ---------- Previous update was at 05:31 PM ----------

cannot you simply do this:

Code:

awk -F, '{print $1, $3}' "${filename}"

I'm not quite sure what you're trying to filter out with the trailing grep......

Hi sorry for being such a n00b. I am trying to grep for a valid ip address in the trailing grep, because the $3 field in the input file has other values other than ip addresses and I am trying to filter for valid ip's. Also I haven't got a valid hostname regex working yet for the $1 field.

Which brings me back to:

Code:

awk -F, '{print $1, $3}' "${filename}"

I'm mainly stuck on finding if they both exist on the same line and if true resolve the hostname to ip.

validating IP addresses is the 'science' on its own as there're so many conditions to consider.
With your simplistic 'grep', you can do something like this:

Code:

awk -F, '$3 ~ "^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$" {print $1, $3}' "${filename}"

Is there a way to add an && operator to the above to check for regex on $1? I tried and it doesn't seem to be working correctly.

Code:

awk -F, '$1 ~ /abc/ && $3 ~ "^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$" {print $1, $3}' "${filename}"

Works fine with Solaris' "nawk"...
Could you elaborate on the 'not working correctly' part, pls?

I got it to work now. However, I am trying to figure out how to enclose this logic into an If statement in bash. Basically, my logic is if a valid hostname and ip appear on the same line then check to see if the hostname resolves to that ip that appears on that line.

I am thinking of passing the hostname ($1) to the host or nslookup command and check if $3 matches the ip address of the output of the host or nslookup command.

thanks