Animation in bash?

Question

bash

Good afternoon! How can I improve the script that draws a bat that moves in different directions. The problem is that the cursor is constantly flickering, before changing the tub it is at the beginning of the terminal, and after drawing the picture it is at the end, respectively. Is there any way to make it smoother? Most likely it's clear. Any suggestions?
And the second question: now the number of lines that fit in one terminal screen is not calculated for me. The `tput rows` function returns an invalid value.
PS the task was given at the university

#!/bin/bash

let y=0
let x=0
let max_x=$(tput cols)
let max_y=24
let wall=0

draw_top() {
    local line1='   ######   ## | ##   #####    '
    local line2='.##############################'
    local line3='   ########################    '
    local line4='      ###################      '
    local line5='            #######            '
    local line6='             ####              '
    local line7='              #                '

    # Сдвиг сверху
    for ((i = 0; i < $1; i++)) ; do
        echo " "
    done

    # Сдвиг слева
    for index in {1..7}; do
        for ((j = 0; j < $2; j++)) ; do
             echo -n " "
        done
        var="line$index"
        echo "${!var}"
    done
}

draw_bottom() { 
    local line1='                #              '
    local line2='              #####            '
    local line3='        ##################     '
    local line4='    ########################   '
    local line5='###############################'
    local line6='  ########   ## | ##   ####### '
    local line7='     ###                 ###   '

    # Сдвиг сверху
    for ((i = 0; i < $1; i++)) ; do
        echo " "
    done

    # Сдвиг слева
    for index in {1..7}; do
        for ((j = 0; j < $2; j++)) ; do
             echo -n " "
        done
        var="line$index"
        echo "${!var}"
    done
}

draw_right() {
    local line1='          #   '
    local line2='          ##  '
    local line3='         #### '
    local line4='       #######'
    local line5='     ######## '
    local line6='     #######  '
    local line7='     ######   '
    local line8='  ##########  '
    local line9='###########-  '
    local line10='  ##########  '
    local line11='     ######   '
    local line12='      ####### '
    local line13='      ########'
    local line14='        ##### '
    local line15='         ###  '
    local line16='          #   '

    # Сдвиг сверху
    for ((i = 0; i < $1; i++)) ; do
        echo " "
    done

    # Сдвиг слева
    for index in {1..16}; do
        for ((j = 0; j < $2; j++)) ; do
             echo -n " "
        done
        var="line$index"
        echo "${!var}"
    done
}

draw_left() {
    local line1='    #       '
    local line2='   ##       '
    local line3='  ####      '
    local line4=' ########   '
    local line5='########    '
    local line6=' #######    '
    local line7='  #######   '
    local line8='##########  '
    local line9=' -##########'
    local line10='##########  '
    local line11='  ########  '
    local line12=' ########   '
    local line13='##########  '
    local line14='  #######   '
    local line15='    ####    '
    local line16='     ##     '

    # Сдвиг сверху
    for ((i = 0; i < $1; i++)) ; do
        echo " "
    done

    # Сдвиг слева
    for index in {1..16}; do
        for ((j = 0; j < $2; j++)) ; do
             echo -n " "
        done
        var="line$index"
        echo "${!var}"
    done
}

move_right() {
    if ((x < max_x - 15))
    then
        ((x++))
    else
        wall=1
    fi

    clear
    draw_right $y $x
}

move_bottom() {
    if ((y < max_y - 8))
    then
        ((y++))
    else
        wall=1
    fi
    
    clear
    draw_bottom $y $x
}

move_left() {
    if (( x > 0 ))
    then
        ((x--))
    else
        wall=1
    fi

    clear
    draw_left $y $x
}

move_top() {
    if (( y > 0 ))
    then
        ((y--))
    else
        wall=1
    fi

    clear
    draw_top $y $x
}

random_choice() {
    RANGE=$1
    number=$RANDOM
    let "number %= $RANGE"
    echo "$number"
}

move() {
    if [ "$1" == 0 ]
    then
        move_right
    fi

    if [ "$1" == 1 ]
    then
        move_left
    fi

    if [ "$1" == 2 ]
    then
        move_top
    fi

    if [ "$1" == 3 ]
    then
        move_bottom
    fi
}

calculate_coords() {
    let vertical=$1

    # Вертикально -> Горизонтально
    if (( vertical > 0))
    then
        x=$((x-8))
        y=$((y+5))

        if (( x < 0 ))
        then
            x=0
        fi

        if (( x + 31 > max_x))
        then
            x=$((max_x-31))
        fi

        if (( y + 8 > max_y))
        then
            y=$((max_y-8))
        fi

    # Горизонтально -> Вертикально
    else
        x=$((x+8))
        y=$((y-5))

        if (( y < 0 ))
        then
            y=0
        fi

        if ((x + 13 > max_x))
        then
            x=$((max_x - 13))
        fi

        if ((y + 17 > max_y))
        then
            y=$((max_y - 17))
        fi
    fi
}

start() {
    current=0
    direction=0
    prevent_direction=0

    while true; do
        # Calculate dicrection
        if ((current == 20 || wall == 1))
        then
            wall=0
            current=0
            prevent_direction=$direction
            direction=$(random_choice 4)

            if (( direction < 2 && prevent_direction > 1 ))
            then
                calculate_coords 0
            fi

            if (( direction > 1 && prevent_direction < 2 ))
            then
                calculate_coords 1
            fi
        fi

        # Move
        move $direction
        current=$((current+1))
        sleep .2
    done
}

start

Answer 1

instead of clear try using "tput cup $y 0" and only make clear on a direction change.
It is also possible to shorten the calculations by calculating the move to the left only when moving left and right.
And use indexes instead of converting the variable name.
And somehow everything is not neat with you. The mouse is crooked, you would paint it more evenly, something like this:

spoiler

#!/bin/bash

let y=0
let x=0
let max_x=120 #$(tput cols)
let max_y=24
let wall=0
let space=""

draw_top() {
    local line[0]='   ###               ###'
    local line[1]='  #####   ## | ##   #####'
    local line[2]='########################### '
    local line[3]='  #######################  '
    local line[4]='     #################   '
    local line[5]='          #######     '
    local line[6]='           ##### '
    local line[7]='             #  '
    local line[8]='              '

    for index in {0..8}; do
        echo "$space${line[$index]}"
    done
}

draw_bottom() { 
    local line[0]='              '
    local line[1]='             #  '
    local line[2]='           ##### '
    local line[3]='          #######     '
    local line[4]='     #################   '
    local line[5]='  #######################  '
    local line[6]='###########################'
    local line[7]='  #####   ## | ##   #####'
    local line[8]='   ###               ###'

    for index in {0..8}; do
        echo "$space${line[$index]}"
    done
}

draw_right() {
    local  line[0]='          #   '
    local  line[1]='          ##  '
    local  line[2]='         #### '
    local  line[3]='       #######'
    local  line[4]='     ######## '
    local  line[5]='     #######  '
    local  line[6]='     ######   '
    local  line[7]='  ##########  '
    local  line[8]='###########-  '
    local  line[9]='  ##########  '
    local line[10]='     ######   '
    local line[11]='     #######  '
    local line[12]='       #######'
    local line[13]='         #### '
    local line[14]='          ##  '
    local line[15]='          #   '

    # Вычисляем сдвиг слева
    space=""
    for ((j = 0; j < $2; j++)) ; do
      space="$space "
    done
    for index in {0..15}; do
        echo "$space${line[$index]}"
    done
}

draw_left() {
    local  line[0]='   # '
    local  line[1]='  ## '
    local  line[2]=' #### '
    local  line[3]='####### '
    local  line[4]=' ######## '
    local  line[5]='  ####### '
    local  line[6]='   ###### '
    local  line[7]='  ########## '
    local  line[8]=' -########### '
    local  line[9]='  ########## '
    local line[10]='   ###### '
    local line[11]='  ####### '
    local line[12]='####### '
    local line[13]=' #### '
    local line[14]='  ## '
    local line[15]='   # '

    # Вычисляем сдвиг слева
    space=""
    for ((j = 0; j < $2; j++)) ; do
      space="$space "
    done
    for index in {0..15}; do
        echo "$space${line[$index]}"
    done
}

move_right() {
    if ((x < max_x - 15))
    then
        ((x++))
    else
        wall=1
    fi

    tput cup $y 0
    draw_right $y $x
}

move_bottom() {
    if ((y < max_y - 8))
    then
        ((y++))
    else
        wall=1
    fi
    
    tput cup $y 0
    draw_bottom $y $x
}

move_left() {
    if (( x > 0 ))
    then
        ((x--))
    else
        wall=1
    fi

    tput cup $y 0
    draw_left $y $x
}

move_top() {
    if (( y > 0 ))
    then
        ((y--))
    else
        wall=1
    fi

    tput cup $y 0
    draw_top $y $x
}

random_choice() {
    RANGE=$1
    number=$RANDOM
    let "number %= $RANGE"
    echo "$number"
}

move() {
    if [ "$1" == 0 ]
    then
        move_right
    fi

    if [ "$1" == 1 ]
    then
        move_left
    fi

    if [ "$1" == 2 ]
    then
        move_top
    fi

    if [ "$1" == 3 ]
    then
        move_bottom
    fi
}

calculate_coords() {
    let vertical=$1

    # Вертикально -> Горизонтально
    if (( vertical > 0))
    then
        x=$((x-8))
        y=$((y+5))

        if (( x < 0 ))
        then
            x=0
        fi

        if (( x + 31 > max_x))
        then
            x=$((max_x-31))
        fi

        if (( y + 8 > max_y))
        then
            y=$((max_y-8))
        fi

    # Горизонтально -> Вертикально
    else
        x=$((x+8))
        y=$((y-5))

        if (( y < 0 ))
        then
            y=0
        fi

        if ((x + 13 > max_x))
        then
            x=$((max_x - 13))
        fi

        if ((y + 17 > max_y))
        then
            y=$((max_y - 17))
        fi
    fi
}

start() {
    current=0
    direction=0
    prevent_direction=0
    clear

    while true; do
        # Calculate dicrection
        if ((current == 20 || wall == 1))
        then
            wall=0
            current=0
            prevent_direction=$direction
            direction=$(random_choice 4)

            if (( direction < 2 && prevent_direction > 1 ))
            then
                calculate_coords 0
            fi

            if (( direction > 1 && prevent_direction < 2 ))
            then
                calculate_coords 1
            fi
            clear
        fi

        # Move
        move $direction
        current=$((current+1))
        /bin/sleep .05
    done
}

start