Simple zsh function to run command every second

monitor.zsh

monitor() {
        heading_template='\[$(date +%T)\] '
        heading_length=11  # "[HH:MM:SS] "=11

        #$(echo -n '{CMD}' | cut -c -$(( $COLUMNS - {heading_length} )) )
        heading_template+="\$( echo -n '$@' | cut -c -\$(( \$COLUMNS - $heading_length )) )"

        heading=$(eval echo -n $heading_template)
        output=$(eval $@ 2>&1)
        while true; do
                echo "\033[4m$heading\033[0m"
                echo $output
                sleep 1

                # calculate next output
                new_output=$(eval $@)

                # then clean previous
                lines=$(echo -n "$output" | wc -l)
                lines=$(( $lines + 1 )) # add header
                echo -n "\033[0G" # move to beginning of line
                for i ({0..$lines}); do
                        echo -n "\033[K\033[F" # clear line and move up
                done
                echo -n "\033[K" # clear line again

                output=$new_output
                heading=$(eval echo -n $heading_template)
        done
}