Want to check whether a command succeeded by redirecting its output to a variable

I'm currently writing a bash script which loads video files up to to YouTube using GoogleCL.

As I'm doing this uploading stuff in a loop (because there can be multiple video files) I would like to check if each file had been uploaded successfully before I upload the next one.

The command google youtube post --access unlisted --category Tech $f (where $f represents the file) outputs a string which tells me whether the upload has been successful or not.

But I don't know how to redirect that "return string" into a variable to do check the successs.

That's what I have:

for f in ./*.ogv ./*.mov ./*.mp4
do
    if [[ '*' != ${f:2:1} ]]
    then
        echo "Uploading video file $f"

        # How to put the return value of the following command into a variable?
        google youtube post --access unlisted --category Tech $f > /dev/null

        # Now I assume that the output of the command above is available in the variable RETURNVALUE
        if [[ $RETURNVALUE == *uploaded* ]]
        then
            echo "Upload successful."
        else
            echo "Upload failed."
        fi
    fi
done

Can anybody help me?