bash script for progression bar

progress-bar.sh

#!/usr/bin/env bash

# Default values
OUTPUT_DIR=""
PREFIX=""
N_IMAGES=0
INTERVAL=3

while [[ ! $# -eq 0 ]]; do  # looping through the arguments
	case "$1" in
		--interval | -i)
			INTERVAL=$2
			;;
		--n-images | -n)
		    N_IMAGES=$2
			;;
		--output-dir | -o)
		    OUTPUT_DIR=$2
			;;
		--prefix | -p)
		    # TODO: Check that if given, it is not empty
		    PREFIX=$2
	esac
	shift
done

if [[ "${OUTPUT_DIR}" != "" && "${OUTPUT_DIR: -1}" != "/" ]]; then
    OUTPUT_DIR="${OUTPUT_DIR}/"
fi

progress=0
n_images_previous=0
start_time=$( date +%s.%N )
while (( $(echo "${progress} < 100" | bc -l) )); do
  end_time=$( date +%s.%N )
  n_images_created="$(ls -1 ${OUTPUT_DIR}${PREFIX}*.png 2> /dev/null  | wc -l)"
  runtime=$( echo "${end_time} - ${start_time}" | bc -l )
  start_time=$( date +%s.%N ) # re-initialize `start_time` after `runtime` has been computed
  progress=$(printf '%.3f\n' $(echo "${n_images_created} / ${N_IMAGES} * 100" | bc -l))
  progress_10=$(printf '%.3f\n' $(echo "${n_images_created} / ${N_IMAGES} * 10" | bc -l))
  n_images_tocreate=$((N_IMAGES - n_images_created))
  speed=$(printf '%.1f\n' $(echo "(${n_images_created} - ${n_images_previous}) / ${runtime}" | bc -l))
  n_images_previous=${n_images_created} # re-initialize `n_images_previous` for the next loop
  if (( $(echo "${speed} == 0" | bc -l) )); then  # to avoid division by zero
    continue
  fi
  etl=$(printf '%.0f\n' $(echo "${n_images_tocreate} / ${speed}" | bc -l))
  etl_toprint=""
  n_hours=$(printf '%.0f\n' $(echo "${etl} / 3600" | bc -l))
  if (( $(echo "${n_hours} >= 1" | bc -l) )); then
    etl_toprint="${n_hours}h "
  fi
  n_min=$(printf '%.0f\n' $(echo "scale=0; (${etl} % 3600) / 60" | bc -l))
  if [[ ${n_min} -ge 1 || ${n_hours} -ge 1 ]]; then
    etl_toprint="${etl_toprint}${n_min}min "
  fi
  n_sec=$(printf '%.0f\n' $(echo "scale=0; ${etl} % 60" | bc -l))
  etl_toprint="${etl_toprint}${n_sec}s"
  pct="$(printf "%.*f\n" 2 ${progress})"
  bar=""
  for (( i=1; i<=10; i++ )); do
    if (( $(echo "${i} <= ${progress_10}" | bc -l) )); then
      bar="${bar}#"
    else
      bar="${bar} "
    fi
  done
  bar="[${bar}]"
  echo -ne "${bar} ${n_images_created}/${N_IMAGES} images created (${pct}%), ETL: ${etl_toprint}, speed: ${speed} images/s\r\c"

  sleep ${INTERVAL}
done