Reading output of shell command in awk script

awkshell

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 –

the call to dig prints a line to the shell
hostname remains null

Best Answer

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

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

Then I can use the hostname anywhere in the script.

Related Solutions

AWK – Handling Multiple Input and Output Files

Suppose that we have a folder full of text files named 000.txt to 181.txt. Here is an example of processing all of them with the same awk script and send them to respective output files (output000.txt - output181.txt):

awk 'NR>6{print>("output" FILENAME)}' {000..181}.txt

If we are using bash, then {000..181}.txt will expand to the names of our 182 input files.

In awk (this may require GNU awk), FILENAME is the name of the input file that awk is currently working on. Thus ("output" FILENAME) is the name of our current output file.

Intended just as an example, the above simply prints all but the first six lines of the input file to the output file. More complicated programs would use the same principles.

Linux – Shell Script output indentation

You could use sed or awk to do this. For example in your main script you could do:

# execute the command and pipe to sed
second-script | sed 's/\(.*\)/  \1/'

The above sed command simply prepends two spaces to each line of output from second-script.

Best Answer

Related Solutions

AWK – Handling Multiple Input and Output Files

Linux – Shell Script output indentation

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