Using Bash to display a progress indicator

In this example using SCP, I'm demonstrating how to grab the process id (pid) and then do something while that process is running.

This displays a simple spinnng icon.

/usr/bin/scp [email protected]:file somewhere 2>/dev/null &
pid=$! # Process Id of the previous running command

spin[0]="-"
spin[1]="\\"
spin[2]="|"
spin[3]="/"

echo -n "[copying] ${spin[0]}"
while [ kill -0 $pid ]
do
  for i in "${spin[@]}"
  do
        echo -ne "\b$i"
        sleep 0.1
  done
done

---

William Pursell's solution

/usr/bin/scp [email protected]:file somewhere 2>/dev/null &
pid=$! # Process Id of the previous running command

spin='-\|/'

i=0
while kill -0 $pid 2>/dev/null
do
  i=$(( (i+1) %4 ))
  printf "\r${spin:$i:1}"
  sleep .1
done

This is a pretty easy technique:
(just replace sleep 20 with whatever command you want to indicate is running)

#!/bin/bash

sleep 20 & PID=$! #simulate a long process

echo "THIS MAY TAKE A WHILE, PLEASE BE PATIENT WHILE ______ IS RUNNING..."
printf "["
# While process is running...
while kill -0 $PID 2> /dev/null; do 
    printf  "▓"
    sleep 1
done
printf "] done!"

The output looks like this:

> THIS MAY TAKE A WHILE, PLEASE BE PATIENT WHILE ______ IS RUNNING...
> [▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓] done!

It adds a ▓ (high density dotted) every second until the process is complete.

If you have a way to estimate percentage done, such as the current number of files processed and total number, you can make a simple linear progress meter with a little math and assumptions about screen width.

count=0
total=34
pstr="[=======================================================================]"

while [ $count -lt $total ]; do
  sleep 0.5 # this is work
  count=$(( $count + 1 ))
  pd=$(( $count * 73 / $total ))
  printf "\r%3d.%1d%% %.${pd}s" $(( $count * 100 / $total )) $(( ($count * 1000 / $total) % 10 )) $pstr
done

Or instead of a linear meter you could estimate time remaining. It's about as accurate as other similar things.

count=0
total=34
start=`date +%s`

while [ $count -lt $total ]; do
  sleep 0.5 # this is work
  cur=`date +%s`
  count=$(( $count + 1 ))
  pd=$(( $count * 73 / $total ))
  runtime=$(( $cur-$start ))
  estremain=$(( ($runtime * $total / $count)-$runtime ))
  printf "\r%d.%d%% complete ($count of $total) - est %d:%0.2d remaining\e[K" $(( $count*100/$total )) $(( ($count*1000/$total)%10)) $(( $estremain/60 )) $(( $estremain%60 ))
done
printf "\ndone\n"

Referred from here is a nice spinner function (with slight modification), will help your cursor to stay in original position also.

spinner()
{
    local pid=$!
    local delay=0.75
    local spinstr='|/-\'
    while [ "$(ps a | awk '{print $1}' | grep $pid)" ]; do
        local temp=${spinstr#?}
        printf " [%c]  " "$spinstr"
        local spinstr=$temp${spinstr%"$temp"}
        sleep $delay
        printf "\b\b\b\b\b\b"
    done
    printf "    \b\b\b\b"
}

with usage:

(a_long_running_task) &
spinner