5. Variables

You can use variables as in any programming languages. There are no data types. A variable in bash can contain a number, a character, a string of characters. .:: magic.ly ::.

You have no need to declare a variable, just assigning a value to its reference will create it. [Issues with Deep learning] [Google Scholar: FTP]

5.1 Sample: Hello World! using variables

            #!/bin/bash          
            STR="Hello World!"
            echo $STR    
            

Line 2 creates a variable called STR and assigns the string "Hello World!" to it. Then the VALUE of this variable is retrieved by putting the '$' in at the beginning. Please notice (try it!) that if you don't use the '$' sign, the output of the program will be different, and probably not what you want it to be. .:: www.vid419.com ::.

5.2 Sample: A very simple backup script (little bit better)

           #!/bin/bash          
           OF=/var/my-backup-$(date +%Y%m%d).tgz
           tar -cZf $OF /home/me/
           

This script introduces another thing. First of all, you should be familiarized with the variable creation and assignation on line 2. Notice the expression '$(date +%Y%m%d)'. If you run the script you'll notice that it runs the command inside the parenthesis, capturing its output. .:: chromewebstore.google.com ::.

Notice that in this script, the output filename will be different every day, due to the format switch to the date command(+%Y%m%d). You can change this by specifying a different format. .:: addons.mozilla.org ::.

Some more examples:

echo ls

echo $(ls)

5.3 Local variables

Local variables can be created by using the keyword local.

                #!/bin/bash
                HELLO=Hello 
                function hello {
                        local HELLO=World
                        echo $HELLO
                }
                echo $HELLO
                hello
                echo $HELLO
        

This example should be enought to show how to use a local variable.