#include <stdio.h>

#include <stdlib.h>

int main() {

    printf("hello ,\n");

    printf("world\n");

    

    // 使用 exit(0) 结束进程

    exit(0);

}

#include <stdio.h>

#include <unistd.h>

int main() {

    printf("hello ,\n");

    printf("world\n");

    

    // 使用 _exit(0) 结束进程，不会执行标准I/O缓冲区的清理操作

    _exit(0);

}

#include <stdio.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <unistd.h>

int main() {

    pid_t pid;

    int status;

    // 创建子进程

    pid = fork();

    if (pid < 0) {

        perror("Fork failed");

        exit(1);

    }

    if (pid == 0) {

        // 子进程

        printf("Child process: pid = %d\n", getpid());

        // 子进程使用 exit(3) 结束

        exit(3);

    } else {

        // 父进程

        printf("Parent process: Child's pid = %d\n", pid);

        // 等待子进程退出并获取其退出状态

        pid_t child_pid = wait(&status);

        if (child_pid == -1) {

            perror("Wait failed");

            exit(1);

        }

        // 使用宏来检查子进程的退出状态

        if (WIFEXITED(status)) {

            int exit_status = WEXITSTATUS(status);

            printf("Child process %d exited with status %d\n", child_pid, exit_status);

        } else {

            printf("Child process %d did not exit normally\n", child_pid);

        }

    }

    return 0;

}

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

int main() {

    // 输出主进程运行标志

    printf("Main process is running\n");

    // 创建子进程

    pid_t pid = fork();

    if (pid < 0) {

        perror("Fork failed");

        exit(1);

    }

    if (pid == 0) {

        // 子进程

        printf("Child process is running\n");

        // 列出当前文件夹下的所有目录和文件

        char *args[] = {"ls", "-l", NULL};

        execvp("ls", args);

        // 如果exec函数调用失败，输出错误信息

        perror("Exec failed");

        exit(1);

    } else {

        // 等待子进程执行完毕

        wait(NULL);

        // 输出主进程运行标志

        printf("Main process is running again\n");

    }

    return 0;

}