Question : Test for interactive vs non-interactive shell

I am trying to incorporate a test into my bash scripts which will select different code depending on whether or not it runs in an interactive or a non-interactive mode.

Given the following two programs:

File: qk.sh
---------------
#!/bin/bash

plen=${#PS1}
if [ -z "$PS1" ]; then
        echo -e "This shell is interactive:$plen :$PS1"
else
        echo -e "This shell is non-interactive:$plen :$PS1"
fi


File2: qk2.sh
-------------
#!/bin/bash
./qk.sh > ckit
cat ./ckit



When I run qk.sh during and interactive session, it prints

"This shell is interactive:0 : "

When I run qk2.sh, which I assume means I am running qk.sh non-interactively, I get the same output.

Any insights would be appreciated.

-G



if [ -z "$PS1" ]; then
        echo This shell is not interactive
else
        echo This shell is interactive
fi

Answer : Test for interactive vs non-interactive shell

if perl -e 'exit -t STDOUT' ; then
        echo -e "This shell is non-interactive:$plen :$PS1"
else
        echo -e "This shell is interactive:$plen :$PS1"
fi