A simple(ish) progress bar in bash

progress.sh

#!/usr/bin/env bash

# Fancy progress bar, in bash!

TOTAL=100
DELAY=0.1

PROGRESS=

get_progress() {
    local perc dperc item total scale cols lines output

    cols=$(tput cols)

    item=$1
    shift
    total=$1

    perc="$(printf "%d/%d\n" "$item" "$total" | bc --mathlib | tr -d '\\\n')"
    dperc="$(printf "%f*100\n" "$perc" | bc --mathlib | tr -d '\\\n')"
    dperc="$(printf "%0.2f" "$dperc")"

    PROGRESS=$(printf "Progress %s%% (%d/%d)" "$dperc" "$item" "$total")
    cols="$(printf "%d-%d\n" "$cols" "${#PROGRESS}" | bc | tr -d '\\\n')"

    width="$(printf "%d*%0.2f\n" "$cols" "$perc" | bc --mathlib | tr -d '\\\n')"
    width="$(printf "%0.0f" "$width")"

    output=
    while (( ${#output} < width )); do
        output="${output}#"
    done

    PROGRESS=$(printf "\033[42m%s\033[49m%s" "$PROGRESS" "$output")

}

update_progress() {
    local lines first_scrollable_line last_scrollable_line progress

    progress=$1
    lines=$(tput lines)
    first_scrollable_line=0
    last_scrollable_line=$(( lines - 1 ))

    # Scoot off the baseline, if we're there
    printf '\n'

    # Save our current cursor
    # (tput sc)
    printf '\033[s'

    # Make a scroll region that excludes the last line
    # ([using tput you don't have to subtract 1] tput csr $(tput lines) 0)
    printf '\033[%d;%dr' "$first_scrollable_line" "$last_scrollable_line"

    get_progress "$i" "$TOTAL"

    # Move cursor to last line, write stuff
    # (tput cup $(tput lines) 0)
    printf "\033[%d;0f\033[K%s" "$lines" "$PROGRESS"

    # Restore our cursor
    # (tput rc)
    printf '\033[u\033[1A'
}

cleanup() {
    local lines

    lines=$(tput lines)

    # Save our current cursor
    # (tput sc)
    printf '\033[s'

    # Clear the last line
    # (tput cup $(tput lines) 0; tput clear)
    printf "\033[%d;0f\033[K" "$lines"

    # Reset scroll region
    printf '\033[0;%dr' "$(tput lines)"

    # Restore our cursor
    # (tput rc)
    printf '\033[u\033[J'
}

main() {
    i=0
    while (( i < TOTAL )); do
        update_progress "$i" "$TOTAL"
        echo "$i -- This. Is Progress"
        sleep "$DELAY"
        (( i++ ))
    done
}

trap cleanup EXIT
main "$@"