In the Unix/Linux shell environment, it’s sometimes necessary to do nothing for an indefinite amount of time. This can be useful when we need to temporarily pause the execution of a script or keep a terminal session open.
Doing nothing may seem simple, but in the Unix/Linux environment, there are several ways to achieve this. In this tutorial, we’ll explore five methods for doing nothing in the shell for an indefinite amount of time.
2. sleep Command
Use the sleep command to pause the execution of a script for a specified amount of time. It can take a numerical argument, which specifies how long (in seconds) to sleep. Or we can pass the infinity argument to it, which essentially does what we want:
$ sleep infinity
This will keep the terminal session open until we manually terminate it.
3. yes Command
To keep a terminal session open indefinitely, we can use the yes command:
$ yes > /dev/null &
This sends the output to the null device and runs the command in the background, effectively discarding the output and keeping the terminal busy with a continuous stream of ‘y’ characters.
4. tail Command
The tail command is a useful tool for displaying the last few lines of a file. By using the command tail -f /dev/null, the terminal session can remain open indefinitely. This is because the -f option causes tail to follow the file until it’s manually terminated, which is useful for keeping a terminal session busy:
$ tail -f /dev/null
On the other hand, the yes method is less resource-intensive than the sleep and tail methods and is ideal for generating an endless stream of characters for use in another command. The sleep and tail methods are useful when waiting for a specified amount of time or continuously reading from a file.
5. while Loop
Let’s use a while loop to execute indefinitely without performing any action:
$ while true; do :; done
The loop will keep running the no-op command (:) until the user manually terminates it.
6. no-op Command
The no-op (no operation) command (:) is used to perform no action. To do nothing indefinitely, we can use it all by itself on the command line:
This is useful when we need to do nothing and keep a terminal session open.
In terms of performance, the no-op command is more efficient than the while loop as it is a simple built-in shell command that does nothing, whereas the while loop involves executing a set of commands repeatedly.
This article covered five simple methods to do nothing in the shell for an indefinite amount of time. We only need to choose the best method for our specific needs, and we can pause the execution of our script or keep a terminal session open with ease.
Whether we need to pause the execution of a script, keep a terminal session open, or need a moment to think, these methods will provide us with the tools we need to do nothing in the shell for an indefinite amount of time.