How to display countdown timer in bash shell script running on Linux/Unix

Posted on in Categories , , last updated June 24, 2017

I want to display a countdown before purging cache from CDN network. Is there an existing command to show a conuntdown from 30..1 as 30,29,28,…1 on Linux or Unix bash shell script?

There are various ways to show a countdown in your shell scripts.

First define your message:
msg="Purging cache please wait..."
Now clear the screen and display the message at row 10 and column 5 using tput:
clear
tput cup 10 5

Next you need to display the message:
echo -n "$msg"

Find out the length of string:
l=${#msg}
Calculate the next column:
l=$(( l+5 ))
Finally use a bash for loop to show countdown:
for i in {30..01}
do
tput cup 10 $l
echo -n "$i"
sleep 1
done
echo

Here is a complete shell script:

#!/bin/bash
# Purpose: Purge urls from Cloudflare Cache
# Author: Vivek Gite {www.cyberciti.biz} under GPL v2.x+
# --------------------------------------------------------
# Set me first #
zone_id="My-ID"
api_key="My_API_KEY"
email_id="My_EMAIL_ID"
row=2
col=2
urls="[email protected]"
countdown() {
        msg="Purging ${1}..."
        clear
        tput cup $row $col
        echo -n "$msg"
        l=${#msg}
        l=$(( l+$col ))
        for i in {30..1}
        do
                tput cup $row $l
                echo -n "$i"
                sleep 1
        done
}
# Do it
for u in $urls
do
     amp_url="${u}amp/"
     curl -X DELETE "https://api.cloudflare.com/client/v4/zones/${zone_id}/purge_cache" \
     -H "X-Auth-Email: ${email_id}" \
     -H "X-Auth-Key: ${api_key}" \
     -H "Content-Type: application/json" \
     --data "{\"files\":[\"${u}\",\"${amp_url}\"]}" &>/dev/null &&  countdown "$u"
 
done
echo

You can run it as follows:
./script.sh url1 url2

POSIX shell version

From this post:

countdown()
(
  IFS=:
  set -- $*
  secs=$(( ${1#0} * 3600 + ${2#0} * 60 + ${3#0} ))
  while [ $secs -gt 0 ]
  do
    sleep 1 &
    printf "\r%02d:%02d:%02d" $((secs/3600)) $(( (secs/60)%60)) $((secs%60))
    secs=$(( $secs - 1 ))
    wait
  done
  echo
)

It can be run as follows:
countdown "00:00:10" # 10 sec
countdown "00:00:30" # 30 sec
countdown "00:01:42" # 1 min 42 sec

Sample session:

Gif 01: countdown demo
Gif 01: countdown demo

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

4 comment

  1. How come you could escape double quotes inside double quote strings like that when it wasn’t possible before ?

      1. That never worked before (syntax error), had to use glueing like someone said to a question of escaping double quotes in a double quote string:

        echo "This is a "'"test"'"."

        Now it works. That was one of the stupidities of Bash, and only now they fixed it.

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