Exploring the functions of the Linux kernel: a detailed introduction to the five major parts

As the core part of the operating system, the Linux kernel is responsible for important functions such as managing hardware resources and providing system calls. This article will delve into the five major parts of the Linux kernel, including process management, file system, network communication, device driver and memory management, and provide a detailed introduction and code examples.

1. Process Management

Creation of Process

In the Linux kernel, the creation of a process is achieved through the fork() system call. Here is a simple example code:

#include <stdio.h>
#include <unistd.h>

int main() {
    pid_t pid = fork();
    
    if (pid < 0) {
        // error handling
        perror("fork failed");
    } else if (pid == 0) {
        // child process
        printf("Child process
");
    } else {
        // parent process
        printf("Parent process
");
    }

    return 0;
}

Scheduling of processes

The Linux kernel uses a scheduler to determine the running order of processes. Scheduling behavior can be affected by adjusting the priority of a process. The following is a sample code to modify the process priority:

#include <stdio.h>
#include <sys/resource.h>

int main() {
    int ret;
    const int priority = 10;
    
    ret = setpriority(PRIO_PROCESS, 0, priority);
    
    if (ret == 0) {
        printf("Set priority successfully
");
    } else {
        perror("setpriority failed");
    }

    return 0;
}

2. File system

Creation and writing of files

Linux kernel provides a series of system calls to create and write files, such asopen(), write(), etc. Here is a simple file writing example:

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
    int fd = open("test.txt", O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR);
    
    if (fd < 0) {
        perror("open failed");
        return -1;
    }

    const char* content = "Hello, Linux!";
    write(fd, content, strlen(content));

    close(fd);

    return 0;
}

Reading and closing files

Similarly, you can use the system call read() to read the file content, and use close() to close the file descriptor. Here is a simple file reading example:

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
    int fd = open("test.txt", O_RDONLY);
    
    if (fd < 0) {
        perror("open failed");
        return -1;
    }

    char buffer[100];
    read(fd, buffer, sizeof(buffer));
    printf("File content: %s
", buffer);

    close(fd);

    return 0;
}

3. Network communication

Socket programming

The Linux kernel supports Socket programming, and network communication can be carried out through Socket. Here is a simple TCP client example:

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>

int main() {
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);

    struct sockaddr_in server_addr;
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));

    const char* message = "Hello, Server!";
    send(sockfd, message, strlen(message), 0);

    close(sockfd);

    return 0;
}

4. Device driver

The device driver in the Linux kernel is an important part of realizing communication between the hardware and the kernel. Device drivers can be loaded by writing kernel modules. The following is a simple character device driver example:

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>

static int __init mydriver_init(void) {
    printk(KERN_INFO "My driver initialized
");
    return 0;
}

static void __exit mydriver_exit(void) {
    printk(KERN_INFO "My driver exited
");
}

module_init(mydriver_init);
module_exit(mydriver_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");

5. Memory management

Memory allocation and release

The Linux kernel provides kmalloc() and kfree() function to perform memory allocation and release operations. Here is a simple memory allocation example:

#include <linux/slab.h>

void* ptr = kmalloc(1024, GFP_KERNEL);
if (!ptr) {
    printk(KERN_ERR "Memory allocation failed
");
}

kfree(ptr);

The above is a detailed introduction to the five major parts of the Linux kernel, including process management, file system, network communication, device driver and memory management. Through the display of code examples, I hope readers can have a deeper understanding of the functions and implementation of the Linux kernel.

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