How to print the Nth column of a text file with AWK using argv

Question

Suppose I have a text file with data separated by whitespace into columns. I want to write a little shell script which takes as input a filename and a number N and prints out only that column. With awk I can do the following:

awk < /tmp/in '{print $2}' > /tmp/out

This code prints out the second column.

But how would one wrap that in a shell script so that a arbitrary column could be passed in argv?

Answer 1

awk -v x=2 '{print $x}'

or in a shell script:

#!/bin/sh
num=$1
awk < /tmp/in -v x=$num '{print $x}' > /tmp/out

Answer 2

awk '{print $'$myvar'}' < /tmp/in > /tmp/out

Where $myvar is your variable column (an integer). Watch out for script injections!