TCP/IP网络编程-进程篇学习笔记

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

int gval = 10;
int main()
{
    pid_t pid;
    int lval = 20;
    gval++, lval += 5;

    pid = fork();

    //子进程
    if (pid == 0)
    {
        gval += 2, lval += 2;
    }
    else
    {
        gval -= 2, lval -= 2;
    }

    //子进程
    if (pid == 0)
    {
        printf("子进程[%d,%d]\n", gval, lval);
    }
    else
    {
        sleep(30);
        printf("父进程[%d,%d]\n", gval, lval);
    }


    printf("猜猜我是啥[%d,%d]\n", gval, lval);
}

#include <sys/wait.h>
pid_t wait(int * statloc);

成功时返回终止的子进程ID, 失败时返回 -1

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

int main()
{
    pid_t pid;
    int status;

    pid = fork();

    //子进程
    if (pid == 0)
    {
        sleep(10);
        return 44;
    }
    else
    {
        wait(&status);
        //正常退出
        if(WIFEXITED(status)){
            printf("获取子进程返回值%d\n", WEXITSTATUS(status));
        }
    }

    printf("猜猜我是啥\n");
}

取子进程返回值44
猜猜我是啥

#include <sys/wait.h>
pid_t waitpid(pid_t pid, int * statloc, int options)

成功时返回终止的子进程ID(或0), 失败时返回 -1

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

int main()
{
    pid_t pid;
    int status;

    pid = fork();

    //子进程
    if (pid == 0)
    {
        return 44;
    }
    else
    {
        while (!waitpid(-1, &status, WNOHANG))
        {
            sleep(3);
            printf("非阻塞等待\n");
        }
        //正常退出
        if (WIFEXITED(status))
        {
            printf("获取子进程返回值%d\n", WEXITSTATUS(status));
        }
    }

    printf("猜猜我是啥\n");
}

非阻塞等待
获取子进程返回值44
猜猜我是啥

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

void keycontrol(int sig)
{
    if (sig == SIGINT)
    {
        puts("CTRL+C pressed.");
    }
}

void child(int sig)
{
    int status;

    waitpid(-1, &status, WNOHANG);
    if (WIFEXITED(status))
    {
        printf("%d\n", WEXITSTATUS(status));
    }
}

int main()
{
    int i;
    pid_t pid;

    signal(SIGINT, keycontrol);
    signal(SIGCHLD, child);

    //假装在运行
    for (i = 0; i < 2; i++)
    {
        pid = fork();
        if (pid == 0)
        {
            puts("我是子进程");
            return 88;
        } else {
            puts("wait...");
            sleep(10);
        }
    }
    return 0;
}

wait...
我是子进程
88
wait...
我是子进程
88

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

#define BUF_SIZE 1024

void read_childproc(int sig)
{
    pid_t pid;
    int status;

    pid = waitpid(-1, &status, WNOHANG);
    printf("removed proc id: %d\n", pid);
}

int main()
{

    //注册子进程信号
    struct sigaction act;
    act.sa_sigaction = read_childproc;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
    sigaction(SIGCHLD, &act, 0);

    int serv_sock = socket(PF_INET, SOCK_STREAM, 0);

    //初始化地址
    struct sockaddr_in serv_addr;
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(9200);

    if (bind(serv_sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1)
    {
        printf("绑定地址失败 \n");
        exit(1);
    }

    if (listen(serv_sock, 5) == 1)
    {
        printf("绑定端口失败 \n");
        exit(1);
    }

    ////////接收请求///////////
    struct sockaddr_in clnt_adr;
    int clnt_sock, adr_sz, str_len;
    pid_t pid;
    char buf[BUF_SIZE];

    while (1)
    {
        adr_sz = sizeof(clnt_adr);
        clnt_sock = accept(serv_sock, (struct sockaddr *)&clnt_adr, &adr_sz);
        if (clnt_sock == -1)
        {
            continue;
        }
        else
        {
            puts("new client connected...");
        }

        pid = fork();
        if (pid == -1)
        {
            puts("-1  -1  -1");
            close(clnt_sock);
            continue;
        }

        //子进程处理
        if (pid == 0)
        {
            //关闭复制到的父文件号
            close(serv_sock);
            while ((str_len = read(clnt_sock, buf, BUF_SIZE)) != 0)
                write(clnt_sock, buf, str_len);

            close(clnt_sock);
            puts("子进程受理");
            //正常退出子进程
            return 0;
        }
        else
        {
            puts("父进程不处理 clnt_sock");
            close(clnt_sock);
        }
    }

    close(serv_sock);
    return 0;
}

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

#define BUF_SIZE 5

int main(int argc, char *argv[])
{
    char message[BUF_SIZE];
    int str_len, recv_len, recv_cnt, i;

    struct sockaddr_in serv_addr, clnt_addr;

    int serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    if (serv_sock == -1)
    {
        printf("socket() error");
        exit(1);
    }

    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    serv_addr.sin_port = htons(9200);

    if (connect(serv_sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1)
    {
        printf("connect() error");
        exit(1);
    }

    while (1)
    {
        fputs("请输入您的信息,按Q键退出\n", stdout);
        fgets(message, 1024, stdin);

        //因为fgets会保留输入中换行符,故判断加\n
        if (!strcmp(message, "q\n") || !strcmp(message, "Q\n"))
        {
            break;
        }

        write(serv_sock, message, strlen(message));
        str_len = read(serv_sock, message, BUF_SIZE);

        printf("Message from server: %s\n", message);
    }

    close(serv_sock);
    return 0;
}