Create a script for PlayOnLinux - Chapter 3: The variables

A variable? It's a new insult?

No, it isn't an insult. The variable is an essential element in programming. It is defined by a name and a value. This value will can vary during the execution of the script.

If you don't understand, read what follows and you will quickly see how it works.

Declaring a variable

There is two possibilities to declare a variable in bash:

1st case:

MY_VARIABLE="My value"

2nd case:

export MY_VARIABLE="My value"

In the first case, the current script only will be able to read the variable. In the second case, all the programs and scripts opened from yours will be able to read this variable

And what is the usefulness of this difference?

Answer in the next paragraph

Reading a variable

Just put a "$" before the name of the variable to read it.

Here is an example of code:

PSEUDO="Tinou"
message "$PSEUDO is the best"

Result:

You can use the variables in all the functions. Whether it's echo, message, question, menu, ...

Sending a command's result in a variable

Do you remember this code?

menu "What do you want to eat this evening?" "Carrots Potatoes Chips"

The result was displayed in the console, but there is a way to don't loose this result in bash. Here is the syntax:

MY_VARIABLE=$(my_command)

Which becomes:

MY_MEAL=$(menu "What do you want to eat this evening?" "Carrots Potatoes Chips")

If we use the previous chapter's code:

MY_MEAL=$(menu "What do you want to eat this evening?" "Carrots Potatoes Chips")
message "This evening, we eat some $MY_MEAL"

I let you try this code by yourself. You can grab the result of "text_field", "question", and even the result of system commands such as "ls", "uname -a", "lspci" in the same way. We will talk about it again in the next chapters