【嵌入式Linux应用开发基础】fork()函数

#include <unistd.h>
pid_t fork(void);

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>

#define PORT 8080

int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    int opt = 1;
    int addrlen = sizeof(address);

    // 创建套接字
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // 设置套接字选项
    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
        perror("setsockopt");
        exit(EXIT_FAILURE);
    }
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);

    // 绑定套接字
    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }
    // 监听连接
    if (listen(server_fd, 3) < 0) {
        perror("listen");
        exit(EXIT_FAILURE);
    }

    while (1) {
        if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
            perror("accept");
            continue;
        }
        pid_t pid = fork();
        if (pid < 0) {
            perror("fork failed");
        } else if (pid == 0) {
            // 子进程处理客户端请求
            close(server_fd);
            // 处理客户端请求的代码
            close(new_socket);
            exit(EXIT_SUCCESS);
        } else {
            // 父进程继续监听新连接
            close(new_socket);
        }
    }
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>

void create_daemon() {
    pid_t pid = fork();
    if (pid < 0) {
        perror("fork failed");
        exit(EXIT_FAILURE);
    }
    if (pid > 0) {
        // 父进程退出
        exit(EXIT_SUCCESS);
    }
    // 子进程继续执行
    // 创建新会话
    if (setsid() < 0) {
        perror("setsid failed");
        exit(EXIT_FAILURE);
    }
    // 改变工作目录
    if (chdir("/") < 0) {
        perror("chdir failed");
        exit(EXIT_FAILURE);
    }
    // 设置文件掩码
    umask(0);
    // 关闭标准输入、输出和错误输出
    close(STDIN_FILENO);
    close(STDOUT_FILENO);
    close(STDERR_FILENO);

    // 守护进程的工作逻辑，例如日志记录
    while (1) {
        // 日志记录代码
        sleep(1);
    }
}

int main() {
    create_daemon();
    return 0;
}

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

int main() {
    pid_t pid = fork();
    if (pid < 0) {
        perror("fork failed");
        exit(EXIT_FAILURE);
    } else if (pid == 0) {
        // 子进程执行外部程序
        char *args[] = {"ls", "-l", NULL};
        if (execvp("ls", args) == -1) {
            perror("execvp failed");
            exit(EXIT_FAILURE);
        }
    } else {
        // 父进程等待子进程结束
        wait(NULL);
    }
    return 0;
}

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

#define MATRIX_SIZE 100
#define NUM_PROCESSES 4

// 矩阵乘法函数
void matrix_multiplication(int start, int end) {
    // 执行矩阵乘法的代码
    for (int i = start; i < end; i++) {
        for (int j = 0; j < MATRIX_SIZE; j++) {
            // 计算矩阵元素
        }
    }
}

int main() {
    pid_t pid;
    int i;
    int chunk_size = MATRIX_SIZE / NUM_PROCESSES;

    for (i = 0; i < NUM_PROCESSES; i++) {
        pid = fork();
        if (pid < 0) {
            perror("fork failed");
            exit(EXIT_FAILURE);
        } else if (pid == 0) {
            int start = i * chunk_size;
            int end = (i == NUM_PROCESSES - 1) ? MATRIX_SIZE : (i + 1) * chunk_size;
            matrix_multiplication(start, end);
            exit(EXIT_SUCCESS);
        }
    }

    // 父进程等待所有子进程结束
    for (i = 0; i < NUM_PROCESSES; i++) {
        wait(NULL);
    }

    return 0;
}

pid_t pid = fork();
if (pid == -1) {
    // 处理错误
} else if (pid == 0) {
    // 子进程代码
} else {
    // 父进程代码
}

if (pid == -1) {
    perror("fork failed");
    exit(EXIT_FAILURE);
}