What is redirection in OS?⌗

Have you heard about redirection in OS? If not then this article is for you. In this article, we will learn about redirection in OS.

Introduce Standard Input, Output, and Error⌗

The photo is from here

Initially, The I/O only happened through a physically connected system console. (input via keyboard, output via monitor), As time passed, the I/O devices(input via mouse, or touch-pad, etc) were added to the system. So, the standard input, output, and error were introduced.

Standard Stream abstracts this aspect to satisfy the program’s needs to customize the input and output. The standard stream is a pre-connected input and output communication channel between a computer program and its environment when it begins execution. The three input/output (I/O) connections are called standard input (stdin), standard output (stdout), and standard error (stderr).

So, Today, we are going to learn about redirection in OS. Let’s get started.

What is redirection?⌗

Redirection is a feature in Linux such that when executing a command, you can change the standard input/output devices. If you do not understand what it is, then don’t worry. I’ll show you some examples.

What is my console’s standard output of the ls -a command? That might be a console.

As you can see, the standard output of ls -a command is a console. But, what if I want to save the standard output of ls -a command to a file? Then, I can use redirection.

ls -a > output.txt

As you can see, the standard output of ls -a command is saved to output.txt file. This is what redirection is.

Redirect Standard Input⌗

The standard input is the default source of data for a program or process. The standard input is usually the keyboard, but it depends on the system. The standard input is usually represented in a program by the file handle stdin.

I’ll show you how to redirect standard input. Let’s say I have an input.txt file that contains the following text.

Hello, World!

And I want to print the text in the input.txt file to the console. Then, I can use redirection.

cat < input.txt

I think you already understand what redirection is. Let’s move on to the next section. I guess you may want to learn about how it works under the hood. So, In the next post, I’m gonna show you about file descriptor.