Bash spinner, WIP.

spinner.sh

#!/bin/bash

TTY=/dev/tty

spin() {
  width=20
  delta=1
  #fwd_chars=("\\" "|" "/" "-")
  #rev_chars=("/" "|" "\\" "-")
  fwd_chars=">"
  rev_chars="<"
  space=0

  "$@" >/dev/null &
  pid=$!

  tput civis
  while kill -0 $pid 2>/dev/null
  do
    if ((delta>0))
    then
      chars=(${fwd_chars[@]})
    else
      chars=(${rev_chars[@]})
    fi

    # make a line of dashes
    for ((i=0; i<width; i++))
    do
      echo -ne "-" >$TTY
    done

    # move to the right offset
    for ((i=0; i<width-space; i++))
    do
      echo -ne "\b" >$TTY
    done

    # animate
    for c in ${chars[@]}
    do
      echo -ne "$c" >$TTY
      sleep 0.075
      echo -ne "\b" >$TTY
    done

    # move back to the left
    for ((i=0; i<space; i++))
    do
      echo -ne "\b" >$TTY
    done

    # clear the line
    for ((i=0; i<width; i++))
    do
      echo -ne " " >$TTY
    done

    # back to the left
    for ((i=0; i<width; i++))
    do
      echo -ne "\b" >$TTY
    done

    ((space+=delta))

    if ((space>=width))
    then
      delta=-1
      ((space+=delta))
      ((space+=delta))
    elif ((space<0))
    then
      delta=1
      ((space+=delta))
      ((space+=delta))
    fi
  done
  tput cnorm
  wait $pid
}

spin sleep 15
echo "Done."