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Custom Operation Scripts and Function Development

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1. What is a Script?

A script is a programming language used for automating tasks. It is generally simpler and more focused on specific types of tasks than a full programming language.

Scripting languages are typically interpreted rather than compiled, meaning that scripts are translated into machine code at runtime. This feature makes scripting languages very useful for rapid development and task automation.

2. The Use of Scripts in System Operations

In system operations, scripts are used to automate various repetitive and scheduled tasks, such as system backups, log analysis, software deployment, and monitoring system status.

Using scripts can significantly reduce the need for manual operations, improve efficiency, reduce errors, and make complex tasks easier to manage.

3. Common Scripting Languages

Common scripting languages include:

  • Shell Scripts (e.g., Bash): Used for automation in Linux and Unix systems.
  • Python: Due to its simplicity and strong library support, it is very suitable for complex system management tasks.
  • Perl: Although less commonly used now, Perl was once very popular for text processing and system management.
  • PowerShell: Very powerful in Windows environments for automation and configuration management.

4. How to Write a Shell Script?

Writing a Shell script typically follows these steps:

  • Define the Interpreter: Specify the interpreter in the first line of the script file (e.g., #!/bin/bash).
  • Write Commands: Write Shell commands as you would enter them in the command line.
  • Add Control Structures: Such as loops (for, while) and conditional statements (if-else) to control the flow of the script.
  • Variables and Parameters: Define variables to store data and pass data to the script through parameters.
  • Error Handling: Add error detection and handling mechanisms to ensure the robustness of the script.
  • Testing and Debugging: Run the script under different conditions to ensure it works as expected.

Each step requires some knowledge of Shell programming, but even beginners can gradually master it through practice and learning.

5. Basic Knowledge of Shell Scripts

Mastering the basic knowledge and commands of Shell scripts is very important. Here are some essential knowledge points and commonly used commands:

  1. Command Line Basics: Understand how to execute commands in the Command Line Interface (CLI).
  2. File and Directory Operations: Familiarize yourself with how to navigate the file system in Shell, such as creating, deleting, moving, and copying files and directories.
  3. File Permissions and Ownership: Understand how to view and modify the permissions and ownership of files and directories.
  4. Environment Variables: Understand the concept of environment variables and how to use them.
  5. Text Processing: Familiarize yourself with basic text processing tools for text files.

6. Common Shell Commands

  1. Navigation Commands: cd (change directory), pwd (print working directory), ls (list directory contents).
  2. File Operations: touch (create an empty file), cp (copy files or directories), mv (move/rename files or directories), rm (remove files or directories).
  3. View and Edit Files: cat (view file content), more/less (paginate file content), nano, vi (text editors).
  4. File Permissions: chmod (change file permissions), chown (change file owner).
  5. Text Processing: grep (text search), awk (text processing), sed (stream editor), cut, sort, uniq.
  6. Pipes and Redirection: Understand how to use pipes (|) to pass the output of one command as input to another, and how to use redirection (>, >>, <) to change the direction of input and output.
  7. Basic Script Writing: Learn how to write simple Shell scripts, including variable declarations, loops (for, while), conditional statements (if-else), and functions.

Advanced Knowledge:

  • Process Management: Understand how to use commands like ps, top, kill, etc., to manage system processes.
  • Network Commands: Understand how to use commands like ping, netstat, ssh, scp, etc., for basic network operations.
  • System Monitoring: Learn to use commands like df, du, free, uptime, etc., to monitor system resources.

By mastering these basic knowledge points and commands, beginners can build a fundamental understanding of Shell scripts and gradually learn more advanced features and techniques.

7. Shell Script Examples

Batch Rename Files: 

#!/bin/bash

# Set file extension
extension=".txt"

# Iterate over all files in the current directory
for file in *${extension}
do
  # Get the filename (excluding the extension)
  filename=$(basename "${file}" "${extension}")
  # Rename the file
  mv "${file}" "${filename}_new${extension}"
done
  • Knowledge Points:
    • Defining and using variables
    • for loop statement
    • mv command

Find and Delete Files with a Specific Name: 

#!/bin/bash

# Set filename
filename="example.txt"

# Find and delete the file
find . -name "${filename}" -delete
  • Knowledge Points:
    • find command

Batch Change File Permissions: 

#!/bin/bash

# Set directory path
dir_path="/path/to/dir"

# Set file permissions (in octal)
permission="644"

# Batch change file permissions
find ${dir_path} -type f -exec chmod ${permission} {} \;
  • Knowledge Points:
    • find command
    • chmod command
    • How to define file permissions

References: