Diff for "BashFAQ/044"

How do I create a progress bar?

The easiest way is to use dialog --gauge. Here is an example, which relies heavily on BASH features:

   # Bash
   # Process all of the *.zip files in the current directory.
   files=(*.zip)
   dialog --gauge "Working..." 20 75 < <(
      n=${#files[*]}; i=0
      for f in "${files[@]}"; do
         # process "$f" in some way (for testing, "sleep 1")
         echo $((100*(++i)/n))
      done)

Here's an explanation of what it's doing:

• An array named files is populated with all the files we want to process.

• dialog is invoked, and its input is redirected from a ProcessSubstitution. (A pipe could also be used here; we'd simply have to reverse the dialog command and the loop.)

• The processing loop iterates over the array.

• Every time a file is processed, it increments a counter (i), and writes the percent complete to stdout.

For more examples of using dialog, see FAQ #40.

A progress bar can also be programmed without any external commands. This example assumes a terminal that uses standard ISO 6429 (a.k.a. ANSI or VT100) escape sequences:

files=(*)
width=$COLUMNS

n=${#files[*]}; i=0
for f in "${files[@]}"; do
  # process "$f" in some way (for testing, "sleep 1")
  printf "\e[40m\e[7m%$(($width*$i/$n))s\n\e[A" " "
  i=$(( $i + 1 ))
done
printf "\e[0m\n"