A variable without the dollar sign $ only provides the name of the variable.To get the value held in a variable, you have to provide the dollar sign $.Variables in quotation marks " are treated as variables.A variable in single quotes ' is treated as a literal string, and not as a variable.For now, here are some things to remember: We’ll talk about quoting variables later. So, you can use the same command that references the same variables and get different results if you change the values held in the variables. If you re-run the previous command, you now get a different result: echo "$my_boost is to $me as $his_boost is to $him (c) $this_year" To assign a new value to the variable, my_boost, you just repeat what you did when you assigned its first value, like so: my_boost=Tequila You can also change the values of variables. The values of the variables replace their names. Let’s use all of our variables at once: echo "$my_boost is to $me as $his_boost is to $him (c) $this_year" You must precede the variable name with a dollar sign $ whenever you reference the value it contains, as shown below: echo $my_name echo $my_boost echo $this_year To see the value held in a variable, use the echo command. We’ll create four string variables and one numeric variable, this_year: me=Dave my_boost=Linux him=Popeye his_boost=Spinach this_year=2019 Giving a variable a value is often referred to as assigning a value to the variable. Note there isn’t a space before or after the equals sign. The format is to type the name, the equals sign =, and the value. Apart from that, you can use any mix of upper- and lowercase alphanumeric characters. It can, however, start with an underscore. A variable name cannot start with a number, nor can it contain spaces.
Your variable names should be descriptive and remind you of the value they hold. To create a variable, you just provide a name and value for it. When you use them in commands and expressions, they are treated as if you had typed the value they hold instead of the name of the variable. Variables are named symbols that represent either a string or numeric value.
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