Unicode block art in Bash for animated progress indicators or sliders

amplitude.sh

export amplitudeChars=( " " ▁ ▂ ▃ ▄ ▅ ▆ ▇ █ )
axis() {
  local negSym="$1"
  local posSym="$2"
  local value="$3"
  local maxAmplitude="$4"

  local amplitudeChar=${amplitudeChars[$( printf "%d" $(( value * ${#amplitudeChars[@]} / maxAmplitude )) )]}
  local percent=$( printf "%03d" $(( value * 100 / maxAmplitude )) )

  if (( $value < 0 )); then
    echo -n "$negSym $amplitudeChar"
  elif (( $value > 0 )); then
    echo -n "$negSym $amplitudeChar"
  else
    echo -n "       "
  fi
}
axis ⬇︎ ⬆︎ 50 100
axis ⬅ ⮕ 50 100

example.sh

#!/bin/bash
set -eu

export seq1=( ▖ ▘ ▝ ▗ )
export seq2=( ▌ ▞ ▀ ▚ ▐ ▞ ▄ ▚ )
export seq3=( ▜ ▟ ▙ ▛ )
export seq4=( ▁ ▂ ▃ ▄ ▅ ▆ ▇ █ ▇ ▆ ▅ ▄ ▃ ▂ )

sym1() {
  echo -n "${seq1[$(( i % ${#seq1[@]} ))]}"
}
sym2() {
  echo -n "${seq2[$(( i % ${#seq2[@]} ))]}"
}
sym3() {
  echo -n "${seq3[$(( i % ${#seq3[@]} ))]}"
}
sym4() {
  echo -n "${seq4[$(( i % ${#seq4[@]} ))]}"
}

export i=0
while true ; do
  echo -ne \
    "\b\b\b\b\b\b\b\b$( sym1 $i ) $( sym2 $i ) $( sym3 $i ) $( sym4 $i ) "
  sleep 0.2
  export i=$(( i + 1 ))
done

test.rt

<window height="250" width="300" duration="1:00:00.00" bgcolor="yellow">
<time begin="0:00:00.00" end="0:00:05.00"/>
<pre>
|    ↑▄         ↑▄   |
| ←▄ ✛ ▄→    ←▄ ✛ ▄→ |
|    ↓▄         ↓▄   |
</pre>
<time begin="0:00:05.00" end="0:00:10.00"/>
<pre>
|               ↑▄   |
| ←▄ ✛          ✛ ▄→ |
|    ↓▄              |
</pre>
<time begin="0:00:10.00" end="0:00:15.00"/>
<pre>
|    ↑▄              |
|    ✛          ✛    |
|               ↓▄   |
</pre>
<time begin="0:00:05.00"/>Hello
</window>

unicode html subtitles.html

<pre><code>
   ⬆︎▄         ⬆︎▄ 
▄⬅  ⮕▄    ▄⬅   ⮕▄ 
   ⬇︎▄         ⬇︎▄ 
</code></pre>
 
<pre><code>
    ↑▄          ↑▄        ↑▄        
▄←  ✛  →▄    ▄← ✛ →▄    ▄←✛→▄
    ↓▄          ↓▄        ↓▄
</code></pre>

<pre><code>
           ↑▄        
▄← ✛       ✛ →▄
   ↓▄      
</code></pre>  

<pre>
   ↑▄         ↑▄  
←▄ ✛ ▄→    ←▄ ✛ ▄→
   ↓▄         ↓▄  
</pre>