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Flow control in a script is handled by comparisons and test statements.

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Let's look how to write some comparison using if statement here is a basic structure of an if statement

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we are using keyboard.

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If and inside the brackets we are putting some condition here is important to have space between brackets

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and condition.

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Otherwise it is an error.

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If that condition is true script will continue with the block of code after then.

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Keyboard by using keyboard f I will be telling the script that if statement ends here and we can continue

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with code which is not part of that if statement

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if we want to tell what statements should be executed when the condition is false we can use keyboard.

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Else In some cases we might want to specify if statement flow based on more conditions.

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So in such cases we are using Elif keyboard basically the flow is following a first condition is true.

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Do some statements and exit if statement errors.

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If second condition is true do some statements and exit.

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If structure.

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Else if cert condition is true.

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Do some statement and exit.

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If structure otherwise continue with statements under else keyboard.

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Some people don't like to put the keyboard down on the next new line so they putting it after the brackets

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that it is necessary to put semicolon after bracket and then the keyboard then this style of writing

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can save us numerous lines of code in our scripts as you see now in the example

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if you want to evaluate more conditions we can use double Ampersand or double bypass if you use double

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ampersand.

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Statements are a process when both conditions are true.

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If you use double type statements are a process.

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If at least the one of the statement is true

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when we want to negate if condition we are using exclamation mark.

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We can put it into brackets on the beginning or we can put it in front of brackets.

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Also there is necessary to have space between exclamation mark and condition and also between exclamation

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mark and bracket

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as a condition we can use fuel types of comparison.

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Mathematical comparison string comparison and file system related test.