What is the principle of linux operating system

Title: In-depth exploration of the principles and code examples of the Linux operating system

Introduction: The Linux operating system has been widely used in the computer field due to its advantages such as stability, security, and open source. This article will deeply explore the principles of the Linux operating system, including process management, file system, memory management, etc., and attach specific code examples to help readers better understand the working principle of the Linux operating system.

1. Process Management

The process is the basic unit that runs as a program in the Linux operating system. Linux ensures the reasonable allocation and scheduling of system resources through process management.

1. Process creation:

Process creation involves the fork() system call, which creates a child process by copying the address space, file descriptor, etc. of the parent process. The specific sample code is as follows:

#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

int main()
{
    pid_t pid;
    pid = fork();
    if (pid < 0)
    {
        fprintf(stderr, "Fork failed");
        exit(-1);
    }
    else if (pid == 0)
    {
        printf("This is child process
");
    }
    else
    {
        printf("This is parent process
");
    }
    return 0;
}

2. Process scheduling:

The Linux scheduler determines the currently running process based on the priority and scheduling policy of the process. Process scheduling is done through the scheduler kernel module. The following is a simple multi-process scheduling sample code:

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

void signal_handler(int signum)
{
    printf("Received signal: %d
", signum);
}

int main()
{
    signal(SIGINT, signal_handler);
    signal(SIGQUIT, signal_handler);
    while (1)
    {
        sleep(1);
    }
    return 0;
}

2. File system

The file system is the mechanism used to manage files and directories in the Linux operating system. Linux uses a tree-like file system structure, starting from the root directory and organizing files through the directory structure.

1. File reading:

File reading is performed by opening a file descriptor and reading the file content. The following is a simple sample code for file reading:

#include <stdio.h>

int main()
{
    FILE *fp;
    char c;

    fp = fopen("test.txt", "r");
    if (fp == NULL)
    {
        printf("Error opening file
");
        return -1;
    }

    while ((c = fgetc(fp)) != EOF)
    {
        printf("%c", c);
    }

    fclose(fp);
    return 0;
}

2. File writing:

File writing is by opening a file descriptor and writing the file content. ongoing. The following is a simple file writing sample code:

#include <stdio.h>

int main()
{
    FILE *fp;

    fp = fopen("test.txt", "w");
    if (fp == NULL)
    {
        printf("Error opening file
");
        return -1;
    }

    fprintf(fp, "Hello World!");

    fclose(fp);
    return 0;
}

3. Memory Management

Memory management is the mechanism used in the Linux operating system to manage system memory. Linux provides a larger memory space through virtual memory and uses page tables for address translation and protection.

1. Memory allocation:

Linux provides a variety of memory allocation functions, such as malloc, calloc, etc. The following is a simple dynamic memory allocation example code:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int *ptr;
    ptr = (int *)malloc(10 * sizeof(int));
    if (ptr == NULL)
    {
        printf("Error allocating memory
");
        return -1;
    }

    // 使用分配的内存
    for (int i = 0; i < 10; i++)
    {
        ptr[i] = i;
    }

    free(ptr);
    return 0;
}

2. Memory protection:

Linux provides protection for process memory through page tables, including reading, Write, execute and other permissions. The following is a simple memory protection sample code:

#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>

int main()
{
    int *ptr;
    ptr = mmap(NULL, sizeof(int) * 10, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    if (ptr == MAP_FAILED)
    {
        printf("Error mapping memory
");
        return -1;
    }

    // 使用内存
    for (int i = 0; i < 10; i++)
    {
        ptr[i] = i;
    }

    // 设置只读权限
    if (mprotect(ptr, sizeof(int) * 10, PROT_READ) == -1)
    {
        printf("Error protecting memory
");
        return -1;
    }

    munmap(ptr, sizeof(int) * 10);
    return 0;
}

Conclusion:

This article briefly introduces the principles of the Linux operating system, including process management, file system and memory management, and attaches the corresponding code example. An in-depth understanding of the principles of the Linux operating system is crucial for development and operation and maintenance personnel. I hope this article can be helpful to readers.

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