ipset command's output not storing to variable

Question

I am building a script to detect if IPSET exists.

#!/bin/bash
str=$(/usr/sbin/ipset test IPsetName 1.1.1.1)

echo "$str" #outputs blank line

if [[ $str = *"The set with the given name does not exist"* ]]; then
  echo "IPsetName not found"
fi

When I run this script I get this output:

ipset v6.29: The set with the given name does not exist

then a blank line for echo "$str" and I don't see the expected output from the if statement.

How to store the ipset command output to the variable?

Answer 1

Thanks to @StephenHarris

ipset command's output is generated on stderr (not stdout) and 2>&1 captures the output to the variable.

str=$(/usr/sbin/ipset test IPsetName 1.1.1.1 2>&1)

if [[ $str = *"The set with the given name does not exist"* ]]; then
   echo "IPsetName not found"
fi

Now this if statement works as expected!