Updates basics_of_linux.md

## 2. Editing text

First let's just clear out something about **standard streams**. Standard streams are the streams that are used to interact between the human computer-user and the machine. There are three standard streams: standard input (stdin), standard output (stdout), and standard error (stderr).

First let's just clear out something about **standard streams**, or **I/O**-streams. Standard streams are the streams that are used to interact between the human computer-user and the machine. There are three standard streams: standard input (stdin), standard output (stdout), and standard error (stderr).

### Stdin

Stdin is the data that gets inputed into the program. An example of a program that requires stdin data is `cp`. In order for the program to do anything it needs input data. For example `cp file1 copy_of_file1`. Here `file1` and `copy_of_file1` is the stdin.

### Stdout

Stdout is the data that get ouputed from the program.

For example, when you use the command `cat file1` that data/text that gets outputed is the stdout. Not all programs have stdout. For example when you use `mv` or `cp` successfully you get no stdout back from the program.

For example, when you use the command `cat file1` that data/text that gets outputed is the stdout The same with the program `ls`. Not all programs have stdout. For example when you use `mv` or `cp` successfully you get no stdout back from the program.

The stdout can be redirected to another file by using these symbols `>` and `>>`. So now we can do the following:

```

ls > result_of_ls.txt

# now the result will be written to the file result_of_ls.txt

ls >> result_of_ls.txt

# This will append the data to the bottom of the file result_of_ls.txt

```

The file descriptor for **stdout** is: **1**