Linux Sleep Command (Pause a Bash Script)

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sleep is a command-line utility that allows you to suspends the calling process for a specified time. In other words, the sleep command pauses the execution of the next command for a given number of seconds.

The sleep command is useful when used within a bash shell script, for example, when retrying a failed operation or inside a loop.

In this tutorial, we will show you how to use the Linux sleep command.

How to Use the sleep Command

The syntax for the sleep command is as follows:

sleep NUMBER[SUFFIX]...

The NUMBER may be a positive integer or a floating-point number.

The SUFFIX may be one of the following:

  • s - seconds (default)
  • m - minutes
  • h - hours
  • d - days

When no suffix is specified, it defaults to seconds.

When two or more arguments are given, the total amount of time is equivalent to the sum of their values.

Here are a few simple examples demonstrating how to use the sleep command:

  • Sleep for 5 seconds:

    sleep 5
  • Sleep for 0.5 seconds:

    sleep 0.5
  • Sleep for 2 minute and 30 seconds:

    sleep 2m 30s

Bash Script Examples

In this section, we’ll go over a few basic shell scrips to see how the sleep command is used.

#!/bin/bash

# start time
date +"%H:%M:%S"

# sleep for 5 seconds
sleep 5

# end time
date +"%H:%M:%S"

When you run the script, it will print the current time in HH:MM:SS format. Then the sleep command pauses the script for 5 seconds. Once the specified time period elapses, the last line of the script prints the current time.

The output will look something like this:

13:34:40
13:34:45

Let’s take a look at a more advanced example:

#!/bin/bash

while :
do
  if ping -c 1 ip_address &> /dev/null
  then
    echo "Host is online"
    break
  fi
  sleep 5
done

The script checks whether a host is online or not every 5 seconds. When the host goes online, the script will notify you and stop.

How the script works:

  • In the first line, we are creating an infinite while loop .
  • Then we are using the ping command to determine whether the host with IP address of ip_address is reachable or not.
  • If the host is reachable, the script will echo “Host is online” and terminate the loop.
  • If the host is not reachable, the sleep command pauses the script for 5 seconds, and then the loop starts from the beginning.

Conclusion

The sleep command is one of the simplest Linux commands. It is used to pause the execution of the next command for a given amount of time.

If you have any questions or feedback, feel free to leave a comment.