progress_bar.sh

#!/usr/bin/env bash
COLUMNS=$(tput cols)
echo $COLUMNS
for i in $(seq 0 $((COLUMNS - 2)))
do
    echo -ne "\033[2K\r"
    echo -n "["
    yes = | head -n $i | tr -d "\n"
    if [ $((COLUMNS - 2 - i)) != 0 ]
    then
        yes " " | head -n $((COLUMNS - 2 - i)) | tr -d "\n"
    fi

    echo -n "]"
    sleep .03
done
echo

I am going to suggest double quotes to prevent globbing and word splitting.

echo "$COLUMNS"
| head -n "$i"