utf8 progress bar

#!/bin/sh

# This would be handy as a script to
# produce variable load for testing

trap "tput cvvis" EXIT

# dash 0.5.5 at least doesn't support \x so we use /usr/bin/
col_base="$(/usr/bin/printf '\x1b')[38;5;"
for i in 229 228 227 226 220 184 178 202 196 160; do
    hlb="$hlb$col_base${i}m▣
"
done

rsleep() {
  printf ".1\n.05\n.02\n.01\n" | shuf | tail -n1
}

tput civis
col=$(tput bold; tput setaf 3)
nc=$(tput sgr0)
count=0
max=10
inc=1
sleep=.1
while true; do
  left=$(($max-$count))
  hl=$(printf "$hlb" | head -n$count | tr -d '\n')
  nl=$(yes □ 2>/dev/null | head -n$left | tr -d '\n')
  printf "\r$hl$nc$nl"
  sleep $sleep
  count=$(($count+$inc))
  [ "$count" -gt $max ] && { count=$max; inc=-1; sleep=$(rsleep); }
  [ "$count" -lt 0 ] && { count=0; inc=1; sleep=$(rsleep); }
done