Bash var doc update (bobbyiliev#113)

* Update 004-bash-variables.md

Another Hacktober Fest PR! I think that inputs in the commandline should also be mentioned!

* Update 004-bash-variables.md

Hello again ^^ another Hacktober Fest PR! I think that reading inputs in the Command Line should also be mentioned!

* Update 004-bash-variables.md

Hello again ^^ another Hacktober Fest PR! I think that reading inputs in the Command Line should also be mentioned!

Author: siwar9

ebook/en/content/004-bash-variables.md

@@ -82,5 +82,52 @@ You would see the following output on your screen:
 ```bash
 Hello DevDojo
 ```
-
 Note that you don't necessarily need to add semicolon `;` at the end of each line. It works both ways, a bit like other programming language such as JavaScript!
+
+
+You can also add variables in the Command Line outside the Bash script and they can be read as parameters:
+
+```bash
+./devdojo.sh Bobby buddy!
+```
+This script takes in two parameters `Bobby`and `buddy!` seperated by space. In the `devdojo.sh` file we have the following:
+
+```bash
+#!/bin/bash
+
+echo "Hello there" $1
+
+```
+`$1` is the first input (`Bobby`) in the Command Line. Similarly, there could be more inputs and they are all referenced to by the `$` sign and their respective order of input. This means that `buddy!` is referenced to using `$2`. Another useful method for reading variables is the `$@` which reads all inputs.
+
+So now let's change the `devdojo.sh` file to better understand: 
+
+```bash
+#!/bin/bash
+
+echo "Hello there" $1
+
+# $1 : first parameter
+
+echo "Hello there" $2
+
+# $2 : second parameter
+
+echo "Hello there" $@
+
+# $@ : all
+```
+The ouput for:
+
+```bash
+./devdojo.sh Bobby buddy!
+``` 
+Would be the following:
+
+```bash
+Hello there Bobby
+Hello there buddy!
+Hello there Bobby buddy!
+```
+
+