The sleep command won’t let your Linux computer do anything. Counterintuitive maybe, but sometimes a period of inactivity is just the thing. This article will teach you how to use this bash shell command effectively.

Using sleep is simple. Enter on the command line sleep , a space, a number, and then press Enter.

                      sleep 5
                    

The cursor disappears for five seconds and then returns. What happened? Using sleep on the command line, instructs Bash to suspend processing for the length of time you specify. In our example that was five seconds.

We can last surrender to sleep in days, hours and minutes as well as in seconds. To do this, add a suffix to either d, h, m, or s with duration. To pause sleep for a day, four hours, seven minutes, and five seconds, use a command like this:

                      sleep 1d 4h 7m 5s
                    

the s Suffix (for seconds) is optional. Without a suffix, sleep treats each duration as seconds. Suppose you wanted to have sleep Pause for five minutes and twenty seconds. A correct format for this command is:

                      sleep 5m 20
                    

If you forget to indicate that m Suffix for the minute, you will instruct sleep pause for five seconds and then again for twenty seconds. So sleep will pause for 25 seconds.

Many commands require you to specify parameters in a specific order, but sleep is very forgiving. You can deploy them in any order and sleep will make sense of them. You can also specify a floating point number as a parameter. To the example, 0.5h is a valid option to indicate your request sleep pause for half an hour.

Tell all of the following (increasingly eccentric) commands sleep Pause for 10 seconds.

                      sleep 10
                    

                      sleep 5 5s
                    

                      Sleep 1 1 1s 1 1 1s 1 2
                    

                      sleep 0.16667m
                    

Use hibernation to pause before a command

the sleep Command can be used to pause before executing a command. This command would pause for 15 seconds and then give a beep.

                      sleep 15 && echo -en '�07'
                    

Use sleep mode to pause between commands

You can use sleep to put a pause between two commands. This command would list the files in your Documents directory, pause for five seconds, and then change the current working directory to your home directory:

                      ls -R ~/Documents && sleep 5 && cd ~
                    

Use sleep mode to pause a script from running

You can use the … sleep Command in shell scripts to pause script execution for a specified time. Typically, you would do this to give a process enough time to complete before the script continues processing. You can also use it to limit the rate at which a script requests another resource.

To demonstrate exactly that, here is a script that can be run using. calls a Google web service curl . If you use the web service with the ISBN Number of a book, it replies with a dump of the JSON data for this book. We can analyze this data by going through the jq Utility to get the title of the book. So that the script doesn’t load the web service, it sleeps for a second between web requests.

Create a file with the following text and save it as check_book.sh .

                      #!/bin/bash

for book in `cat $1`
do
 echo $book":"
 curl -s https://www.googleapis.com/books/v1/volumes?q=isbn:$book | jq '.items | .[] | .volumeInfo.title'
 echo ""
 sleep 1
done

echo "All done."
                    

Enter the following command to set execute permissions and make the script executable.

                      chmod +x check_book.sh
                    

The script requires the curl and jq Utilities. Use apt-get to install these packages on your system if you are using Ubuntu or any other Debian based distribution. For other Linux distributions, use your Linux distribution’s package management tool instead.

                      sudo apt-get install curl
                    

                      sudo apt-get install jq
                    

Create a text file with the following numbers and save it as books.txt .

                      9781565921276
9781874416685
9781565921672
9780521431088
9781491941591
                    

Run the check_book.sh Script and pass that books.txt File as a parameter.

                      ./check_book.sh books.txt
                    

The inquiries are sent to the Google web service every second. The title of the book appears shortly after each ISBN number is queried.

That’s all there is sleep . The inner workings of the check_book.sh Scripting is beyond the scope of this article. The script was chosen solely to ensure valid use of the sleep Command. If you want to learn more about the two main components of the script, check out the curl Project page and the jq Online manual .

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