How to add a progress bar to a shell script?

Question

When scripting in bash or any other shell in *NIX, while running a command that will take more than a few seconds, a progress bar is needed.

For example, copying a b

Answer 1

Here is how it might look

Uploading a file

[##################################################] 100% (137921 / 137921 bytes)

Waiting for a job to complete

[#########################                         ] 50% (15 / 30 seconds)

Simple function that implements it

You can just copy-paste it to your script. It does not require anything else to work.

PROGRESS_BAR_WIDTH=50  # progress bar length in characters

draw_progress_bar() {
  # Arguments: current value, max value, unit of measurement (optional)
  local __value=$1
  local __max=$2
  local __unit=${3:-""}  # if unit is not supplied, do not display it

  # Calculate percentage
  if (( $__max < 1 )); then __max=1; fi  # anti zero division protection
  local __percentage=$(( 100 - ($__max*100 - $__value*100) / $__max ))

  # Rescale the bar according to the progress bar width
  local __num_bar=$(( $__percentage * $PROGRESS_BAR_WIDTH / 100 ))

  # Draw progress bar
  printf "["
  for b in $(seq 1 $__num_bar); do printf "#"; done
  for s in $(seq 1 $(( $PROGRESS_BAR_WIDTH - $__num_bar ))); do printf " "; done
  printf "] $__percentage%% ($__value / $__max $__unit)\r"
}

Usage example

Here, we upload a file and redraw the progress bar at each iteration. It does not matter what job is actually performed as long as we can get 2 values: max value and current value.

In the example below the max value is file_size and the current value is supplied by some function and is called uploaded_bytes.

# Uploading a file
file_size=137921

while true; do
  # Get current value of uploaded bytes
  uploaded_bytes=$(some_function_that_reports_progress)

  # Draw a progress bar
  draw_progress_bar $uploaded_bytes $file_size "bytes"

  # Check if we reached 100%
  if [ $uploaded_bytes == $file_size ]; then break; fi
  sleep 1  # Wait before redrawing
done
# Go to the newline at the end of upload
printf "\n"