How do I Sleep in a Bash Script?

When you create your Bash scripts, their functionality is such that you have to wait for some function within it to complete its processing before proceeding further. The wait within a Bash script is introduced with the “sleep” command. The sleep command in Bash allows you to wait for as long as you want before doing any further processing. This functionality finds a special use case while dealing with clients and servers in Linux.

Multiple clients can connect to a single server depending upon its request handling capacity in a client-server model. A client always initiates a connection request, whereas a server listens to this request. However, at times, a server might be busy processing other requests. Therefore, there should be a time duration defined for the client for which that client should wait before canceling the connection initiation request. This time duration can be defined while making use of the sleep command.

This was just a simple use case of the sleep command with the client-server model; however, this command can also serve other different purposes within this model. Our motive is to learn how we can sleep in a Bash script in Ubuntu 20.04. For doing that, we have designed this tutorial so that you will get the maximum benefit out of it once you follow the examples shared in it.

How do I Sleep in a Bash Script in Ubuntu 20.04?

For sleeping within a Bash script, the command that is used is known as “sleep”. For your ease, the syntax of this command is stated below:

Here, duration refers to the number of seconds, minutes, hours, or days for which you want your program to sleep. The default sleep duration is in seconds, which means that if you execute the command “sleep 2”, your program will simply sleep for 2 seconds. However, if you want your program to sleep for minutes, hours, or days, then you will have to use the “m”, “h”, or “d” characters after the sleep duration for specifying the minutes, hours, or days respectively.

Now, to understand the working of the sleep command in a better way, you will have to read through the following examples that we have especially designed for you to get your hands on the usage of the sleep command in Bash in Ubuntu 20.04.

Example # 1: Simple Usage of the Sleep Command in Bash:

The first example is the simplest one of all in which we just intended to teach you how you can create a Bash script that uses the sleep command. The sample Bash script is shown below:

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We have just used the sleep command in this script followed by the sleep duration, which in our case was 2. It means that our script will sleep for two seconds before doing any further processing. After sleeping for two seconds, we wanted our script to print a random message on the terminal with the help of the “echo” command.

Now, to execute this script through the Ubuntu 20.04 terminal, we will run the subsequent command in it:

Sleep.sh is the file’s name in which our Bash script for this specific example is written.

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Once this command was executed, our terminal waited for 2 seconds before displaying the message stated in our script on the terminal, as shown in the image below:

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You will verify it once you create a similar Bash script and execute it on your Ubuntu 20.04 system.

Example # 2: Using the Sleep Command to Compare Two Different Times in Bash:

Now we want to take you a little further with the usage of the sleep command in Bash in Ubuntu 20.04. For that, you should first take a look at the following Bash script that we have designed:

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In this Bash script, we first used the date command to print the current system time in the “hours, minutes, seconds” format. After that, we have used the sleep command for putting the script to sleep for 2 seconds. Then again, we have used the date command to print the current system time. Basically, we wanted to compare the two different times, or in other words, we wanted to check whether our sleep command has actually put our script to sleep for 2 seconds or not.

This Bash script can be executed with the same command that we used in our first example. We have displayed the output of this script in the image shown below:

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In this output, you can notice the difference between the two times. The first time was 18:26:06, after which our Bash script slept for 2 seconds. The second time was 18:26:08. Both times differ exactly by 2 seconds which implies that our sleep command has been executed correctly.

Example # 3: Using the Sleep Command within a For Loop in Bash:

Finally, we will now design an example Bash script that will use the sleep command within the “for loop”. You can first take a look at the following Bash script that we have designed for this purpose:

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This Bash script starts with declaring an array named “numbers,” and three values, i.e., 1, 2, and 3 were assigned to this array, meaning that the declared array has three elements. Then, we have a variable to which we have assigned the length of this array so that our “for loop” can easily iterate through this array. Then, we have our “for loop,” which will have a total of three iterations since it iterates through the length of the “numbers” array, which is 3. Within this “for loop,” we wanted to print the elements of our “numbers” array one by one with 1 -the second pause before printing the next value. That is why we have first used the “echo” command to print the array index value followed by a random message. Then our script will sleep for one second, after which the next value will be printed.

This script will be executed in the same manner as we executed our first two example scripts. The output of this Bash script is shown in the image below:

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You can easily visualize from the output shown above that our Bash script slept exactly for a second after printing each index value of our “numbers” array.

Conclusion:

This article started with a brief description of the sleep command in Bash in Ubuntu 20.04 system, followed by its general syntax. Then, we shared three different examples that use this command within a Bash script with you. These examples started with a very easy to complexity level and rose to a relatively difficult complexity level. However, our main goal was to show you how to use the sleep command in a Bash script on Ubuntu 20.04 system. Hopefully, by going through this tutorial, you will be able to use the sleep command within your Bash scripts very efficiently.