Making a progress bar in BASH fixed at the bottom of terminal

Question

I have made a pretty basic progress bar in BASH like this :-

doned=$1  #amount completed
total=$2  #total amount


doned=`echo $doned $total | awk '{print ($1/$2)}'`
total=`tput cols | awk '{print $1-10}'`
doned=`echo $doned $total | awk '{print int(($1*$2))}'`


echo -n $doned"% [ "

for i in $(seq 1 $doned); do
    echo -n "="
done

for i in $(seq $((doned+1)) $total); do
    echo -n "-"
done

echo " ]"

This works exactly like I want it to.

This script runs within a loop in another script. I want it to always display at the bottom of the terminal, or any other fixed place.

The loop is somewhat like this:-

for i in 10 20 30 40; do
    echo -n "Do you want to continue on to the next step? (y/n): ";
    read $yn
    if [[ "$yn" == "n" ]] || [[ "$yn" == "N" ]]; then
        exit 1; # stop the script
        d_3=0;
    fi
    doned=`some command` ### Get number of completed files
    totalss=`some other command` ### Get total number of files
    bash ./libraries/prog.sh $doned $totalss
done

So what I want is that the progress bar remain at the bottom even when inputting values, or displaying something. Is there a way to do this, preferably without having to install anything extra? Most of the computers I want to use this script on are either Debian version 8+ or Ubuntu 16+ systems

Answer 1

Maybe, but I think it's going to be harder than you expect.

You can make the cursor move around the terminal by outputting ANSI control codes. For more on them, see here.

In principle, you could move the cursor to your progress bar, add an =, and then move it back to wherever you plan to print output. Then on the next = you'd have to do it again... but this would probably be ugly.

If you're willing to depart from bash, you can probably find libraries that make this kind of thing easier (like this).

Answer 2

I wrote a testing script to try and do what @MatrixManAtYrService suggested. I realized that this solution does not apply to all systems covered by U&L SE, but this works within the specifications I asked for.

#!/bin/bash

# go to last line and print the empty progress bar
tput sc #save the current cursor position
tput cup $((`tput lines`-1)) 3 # go to last line
echo -n "[" # the next 5 lines just print the required stuff to make the bar
for i in $(seq 1 $((`tput cols`-10))); do
    echo -n "-"
done
echo -n "]"
tput rc # bring the cursor back to the last saved position


# the actual loop which does the script's main job
for i in $(seq 0 10 100); do
    # print the filled progress bar
    tput sc  #save the current cursor position
    doned=${i}  #example value for completed amount
    total=100   #example value for total amount

    doned=`echo $doned $total | awk '{print ($1/$2)}'` # the next three lines calculate how many characters to print for the completed amount
    total=`tput cols | awk '{print $1-10}'`
    doned=`echo $doned $total | awk '{print int(($1*$2))}'`


    tput cup $((`tput lines`-1)) 4 #go to the last line
    for l in $(seq 1 $doned); do #this loop prints the required no. of "="s to fill the bar
        echo -n "="
    done
    tput rc #bring the cursor back to the last saved position

    # the next 7 lines are to find the row on which the cursor is currently on to check if it 
    # is at the last line 
    # (based on the accepted answer of this question: https://stackoverflow.com/questions/2575037/)
    exec < /dev/tty
    oldstty=$(stty -g)
    stty raw -echo min 0
    tput u7 > /dev/tty
    IFS=';' read -r -d R -a pos
    stty $oldstty
    row=$((${pos[0]:2} - 1))


    # check if the cursor is on the line before the last line, if yes, clear the terminal, 
    # and make the empty bar again and fill it with the required amount of "="s
    if [ $row -gt $((`tput lines`-2)) ]; then
        clear
        tput sc
        tput cup $((`tput lines`-1)) 3
        echo -n "["

        for j in $(seq 1 $((`tput cols`-10))); do
            echo -n "-"
        done
        echo -n "]"
        tput cup $((`tput lines`-1)) 4
        for k in $(seq 1 $doned); do
            echo -n "="
        done
        tput rc
    fi

    # this is just to show that the cursor is behaving correctly
    read -p "Do you want to continue? (y/n)" yn;  

done

 # the next few lines remove the progress bar after the program is over   
tput sc # save the current cursor position
tput cup $((`tput lines`-1)) 3 # go to the line with the progress bar
tput el # clear the current line
tput rc # go back to the saved cursor position

There must be better ways to handle overflow into the last line, instead of clearing the terminal, among other things. This serves more as a proof of concept of what @MatrixManAtYrService suggested. Any improvements or comments on its limitations are welcome

Answer 3

An easy way to get progress bars in a shell script is to use whiptail or dialog, as mentioned in comments. One or both should be available on most linux distros.

OP mentioned the aptitude installer in comments. Aptitude is a binary which uses the ncurses library, as does dialog.