eos-waiting-indicator

#!/bin/bash

# Show a waiting indicator on the terminal.
# Usage: eos-waiting-indicator lock-file

DIE() {
    echo "Error: $1" >&2
    exit 1
}

ShowIndicator() {
    local str items
    # items=( "◡◡" "⊙⊙" "◠◠" )
    # items=( "◴" "◷" "◶" "◵" )
    # items=( "▁" "▂" "▃" "▄" "▅" "▆" "▇" "█" "▇" "▆" "▅" "▄" "▃" "▁" )
    items=( "◢" "◣" "◤" "◥" )

    tput civis   # hide cursor
    #printf "%s\n" "$prompt" >&2
    case "$1" in
        -nl) printf "\n" >&2 ;;
    esac
    while true ; do
        for str in "${items[@]}" ; do
            printf "\r%s %s" "$prompt" "$str" >&2
            if [ ! -r "$lockfile" ] ; then
                tput cnorm # unhide cursor
                return
            fi
            sleep 0.25
        done
    done
}

Main()
{
    local lockfile="$1"
    local prompt="$2"

    [ -n "$lockfile" ] || DIE "lockfile argument missing"
    [ -r "$lockfile" ] || DIE "lockfile does not exist"

    ShowIndicator -nl
}

Main "$@"