Mastering Linux: A Guide to Effective Conditional Statements（linux条件判断）
Linux is an open-source operating system that can do nearly anything. It powers everything from desktop computers and phones to web servers that serve websites, applications, and services across the world. Although it has a reputation for being a bit intimidating, it doesn’t have to be. One of the most powerful features of Linux is its ability to use conditional statements which allow you to automate certain tasks. In this guide, you will learn the basics of using conditional statements with Linux to save time and effort.
Conditional statements are programs that check and test certain conditions. Depending on the result of the test, one of two possible actions can be taken. For example, if the temperature is at or below zero, a script can be written to shut down a computer. The syntax and implementation of conditional statements in Linux is similar to other programming languages. It uses the following logic: if something is true, then do something.
The most common type of conditional statement used in Linux is the if-then statement. The simplest form of the if-then statement looks like this:
//conditional statement example
if (condition){
action;
}
The condition is the expression that is evaluated. If the condition evaluates to true, then the action will be performed. For example, if the temperature is at or below zero, then a script can be used to shut down a computer.
In addition to if-then statements, there are several other types of conditional statements that can be used in Linux. For example, the if-else statement allows you to perform different actions depending on the result of the condition. In the following example, if the temperature is at or below zero, then the computer will be shut down, if the temperature is above zero, then the computer will be left on:
//conditional statement example
if (temperature
//shut down computer
shutdown();
} else {
//leave computer on
leaveOn();
}
Conditional statements can also be used to loop through a list or array of data and perform an action. This is known as a ‘loop’ and can be useful when you need to iterate through a large amount of data. For example, let’s say you have a list of 1000 computer files and you want to delete any file over 1GB in size. In order to do this, you could use a loop to iterate through the list and delete any file over 1GB.
//conditional statement example
for (int i = 0; i
if (files[i].size > 1GB){
delete files[i];
}
}
These are just a few examples of how you can use conditional statements with Linux. In order to truly master this powerful tool, you will need to become familiar with the syntax and commands that are available. With practice and patience, you will be creating your own scripts in no time.
