How to do shell scripting?

With the continuous development of computer technology, Shell scripting language is becoming more and more popular among programmers. Shell scripting language can help programmers realize automated operations, batch processing and other functions, greatly improving programmers' work efficiency and work quality. However, for some novices, the operation of Shell script language may be difficult. Here is an introduction to how to operate Shell script.

First of all, what is a shell script?

Shell script is a text file that can be executed in the Shell (operating system command interpreter). It is usually used for script programming in operating systems such as Linux and Unix, and can implement various functions such as loops, conditional branches, and functions.

Then, the prerequisite for learning Shell scripts is to be familiar with the basic commands of operating systems such as Linux and Unix.

Next, we will introduce the operation of Shell script:

1. Create Shell script

In Linux and Unix, we usually use a text editor Such as vim, gedit, etc. to create Shell scripts. Enter the following command on the command line to create a script named test.sh:

$ vim test.sh

2. Add command

After creating the Shell script, we need to add Some commands to achieve certain functions. In a Shell script, each command requires a separate line. The first character in the command line must be "#" or a space, otherwise the content written in the line will be treated as a command. Here is a simple example:

#!/bin/bash
echo "Hello World"

This is a simple Shell script consisting of two lines. The first line specifies using bash as the Shell interpreter; the second line uses the echo command to output the Hello World string.

3. Give the script execution permission

After creating the Shell script, we need to give it execution permission. In Linux and Unix, use the chmod command to give the script execution permission:

$ chmod +x test.sh

4. Run the Shell script

After giving the script execution permission, we can run the Shell script . Enter the following command on the command line to run the test.sh script:

$ ./test.sh

5. Diagnostic Shell Script

In the process of running the Shell script, we may encounter Some bugs and issues. In order to better diagnose the Shell script, you can use the set command to turn on the debugging mode. In the debugging mode, you can output more detailed information:

#!/bin/bash
set -x
echo "Hello World"
set +x

In this example, we turn on the debugging mode through the set -x command. You can see more detailed information before outputting Hello World to facilitate troubleshooting. The set command can also enable other debugging modes. For example, set -e can automatically exit when the script execution fails.

6. Loops and conditional branches

In addition to simple command operations, Shell scripts also support advanced operations such as loops and conditional branches. For example, you can use a for loop to traverse an array:

#!/bin/bash
fruits=("apple" "banana" "orange")
for fruit in "${fruits[@]}"
do
    echo "I like $fruit"
done

In this example, we define an array fruits, and use a for loop to output the contents of each element in the array.

Shell scripts also support conditional branch statements such as if and else, for example:

#!/bin/bash
password="123456"
if [ "$password" == "admin" ]
then
    echo "Welcome"
else
    echo "Access Denied"
fi

In this example, if $password is equal to admin, Welcome is output, otherwise Access Denied is output.

Summary

Shell script is a very practical programming language that can help programmers realize various functions such as automated operations and batch processing. Of course, to learn the Shell scripting language well, you need to have a certain understanding of the basic commands of operating systems such as Linux and Unix. By learning the above methods of Shell script operation, I believe that readers have a certain understanding and mastery. I hope everyone can learn the Shell scripting language well and improve their work efficiency and work quality.

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