Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have a text file with a list ip addresses and other information.

I am using an awk script to process this list and output various computations. I want to call dig -x from inside the awk script and use the returned value.

I have tried

hostname = system("dig +short -x" ip_address);

but what occurs is -

  1. the call to dig prints a line to the shell

  2. hostname remains null

share|improve this question
up vote 9 down vote accepted

Figured it out, but please feel free to add better answers

cmd = "dig +short -x " ;
cmd ip_address | getline hostname;

Then I can use the hostname anywhere in the script.

share|improve this answer
This is the correct way to do it. You will probably want to do close(cmd) afterwards. – Dennis Williamson Jan 7 '11 at 18:44
Yes thanks, found out about that after this posting, will close the question in 2 days(superuser requirement) – bryan Jan 7 '11 at 19:06

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.