A bash script for controlling the cursor (with a few tests)

cursor.sh

#!/bin/bash

# A library of bash functions for moving the cursor around.


function main()
{
    # Run the basic test
    run_test

    echo ""

    # Run the progress bar test
    # 
    # The only cursor control used
    # for the progress bar is 
    # the c_clear_up function.
    run_progress_bar_test
}

# Cursor movement functions

### Clears the current line
### Starting with the cursor
function c_clear()
{
    printf '\033[K';
}

### Moves the cursor to the
### beginning of a line.
function c_start()
{
    printf '\r';
}

### Moves the cursor to the
### beginning of a line and
### clears the whole line.
function c_start_clear()
{
    c_start
    c_clear
}

### Moves the cursor up
### $1 lines.
function c_up()
{
    for i in `seq 1 $1`; do 
        printf '\033[1A'
    done;    
}

### Moves the cursor up $1
### lines and clears each
### line as it goes.
### Cursor will end up
### at the begging of the
### last line.
function c_clear_up()
{
    c_start
    c_clear

    for i in `seq 1 $1`; do 
        printf '\033[1A'
        c_clear
    done;
}

### Moves the cursor back
### $1 columns.
function c_back()
{
    printf "\033[$1D"
}

### Moves the cursor back
### $1 columns and then
### clears the line from
### the cursor to the end
### of the line.
function c_clear_back()
{
    c_back $1
    c_clear
}

### Moves the cursor to
### line $1 and column $2.
function c_move()
{
    printf '\033[$1;$2H'
}


### Tests

function run_test()
{
    echo "Basic Tests..."
    echo ""
    echo "This is the first line."
    echo "This is the second line, I will be replaced in 2s..."
    sleep 2
    c_clear_up 1
    echo "I've been replaced, but now i will count down.."
    echo -n "3"
    sleep 2
    c_start_clear
    echo -n "2"
    sleep 2
    c_start_clear
    echo -n "1"
    sleep 2
    c_start_clear
    echo -n "0"
    sleep 2
    c_start_clear
    echo "The countdown is finished."
    echo -n "This line will be written twice starting here: First line"
    sleep 3
    c_clear_back 10
    echo "Second line"

    echo -n "This line will be fully re-written"
    sleep 3
    c_start_clear
    echo "See? It's been fully re-written."
}

function run_progress_bar_test()
{
    echo "Progress bar test..."

    PROGRESS_BAR_LENGTH=20
    PROGRESS_BAR_VALUE=0

    # We start with a new line in order
    # to add a nicer spacing between our
    # progress bar and everything else.
    echo ""

    # Then we add another new line since
    # after each time we print our our progress
    # bar we are writing a new line.
    echo ""

    # Define the last char (We'll make this dance.)
    # Integers correspond to charactesr.
    LAST_CHAR=0

    while [ $PROGRESS_BAR_VALUE -lt `expr $PROGRESS_BAR_LENGTH + 1` ]; do
        # Move up one line, and clear the full line.
        c_clear_up 1

        # Begin printing the progress bar
        echo -n "    Loading ["

        # Print the current value of the progress bar
        for i in `seq 0 $(expr $PROGRESS_BAR_VALUE - 1)`; do
            echo -n ":"
        done

        # Print the last character, the dancing character, for the progress bar
        if [[ "$PROGRESS_BAR_VALUE" == "$PROGRESS_BAR_LENGTH" ]]; then
            echo -n ":"
        else
            # Print last char in bar based on the integer value
            if [[ "$LAST_CHAR" == "0" ]]; then
                echo -n "/"
            elif [[ "$LAST_CHAR" == "1" ]]; then
                echo -n "-"
            elif [[ "$LAST_CHAR" == "2" ]]; then
                echo -n "\\"
            elif [[ "$LAST_CHAR" == "3" ]]; then
                echo -n "|"
            elif [[ "$LAST_CHAR" == "4" ]]; then
                echo -n "/"
            elif [[ "$LAST_CHAR" == "5" ]]; then
                echo -n "-"
            elif [[ "$LAST_CHAR" == "6" ]]; then
                echo -n "\\"
            elif [[ "$LAST_CHAR" == "7" ]]; then
                echo -n "|"
            fi

            # Move to the next frame in the animation
            LAST_CHAR=`expr $LAST_CHAR + 1`

            # Check if we have reached the end of our animation
            # and if so, go back to the beginning.
            if [[ "$LAST_CHAR" == "8" ]]; then
                LAST_CHAR=0
            fi
        fi

        # Print the remaining space in the progress bar
        for i in `seq 1 $(expr $PROGRESS_BAR_LENGTH - $PROGRESS_BAR_VALUE)`; do
            echo -n ' '
        done

        # Finalize the progress bar
        echo -n "] "

        # Print the percentage
        let PERCENT="(100 * $PROGRESS_BAR_VALUE) / $PROGRESS_BAR_LENGTH"
        if [[ "$PERCENT" == "100" ]]; then
            PERCENT="$PERCENT% DONE!"
        else
            PERCENT="$PERCENT%"
        fi
        echo $PERCENT

        # Update the progress bar value
        PROGRESS_BAR_VALUE=`expr $PROGRESS_BAR_VALUE + 1`

        # Sleep
        sleep 0.2
    done;

    # Print out another new line in order to 
    # add a buffer under the progress bar.
    echo ""

}

# Initialize the Main function
main