bash scripting and awk help

streetfighter2 · September 10, 2009, 5:16pm

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:

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

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.

vgersh99 · September 10, 2009, 5:34pm

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

cannot you simply do this:

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

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

streetfighter2 · September 10, 2009, 5:54pm

vgersh99:

To keep the forums high quality for all users, please take the time to format your posts correctly.

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```text
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```
by hand.)

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

cannot you simply do this:
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:

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.

vgersh99 · September 10, 2009, 6:14pm

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:

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

streetfighter2 · September 10, 2009, 11:11pm

vgersh99:

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:
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.

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

vgersh99 · September 11, 2009, 9:23am

streetfighter2:

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.
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?

streetfighter2 · September 11, 2009, 11:18am

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