LIUNX系统编程：进程间通信-管道（2）

news2024/12/29 9:32:45

1.管道通信的4种情况

1.1管道内没有数据&&写端不关闭

1.2管道内数据被写满&&写端不关闭

1.3写端写了一部分，关闭写端

1.4读端不读直接关闭，写端再写

1.管道通信的4种情况

1.1管道内没有数据&&写端不关闭

代码验证

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

void Write(int fd)
{
    char buffer[128];
    int cnt = 0;
    while(1)
    {
        sleep(1000);//sleep不向管道写入
        sprintf(buffer,"I am childProcess,I'm writing pid:%d cnt = %d\n",getpid(),cnt);
        write(fd,buffer,sizeof(buffer));
        cnt++;
    }
}

void Read(int fd)
{
    char buffer[1024];
    while(1)
    {
        read(fd,buffer,sizeof(buffer)-1);
        printf("i am father process,I am reading\nmessage:%s\n",buffer);
    }

}


int main()
{
   int fdarry[2] = {0};
    int ret = pipe(fdarry);
    if(ret == -1)
    {
        printf("Create pipe fail");
        return -1;
    }

    pid_t pid = fork();

    if(pid == 0)
    {
        //子进程写
        close(fdarry[0]);
        Write(fdarry[1]);
    }
    close(fdarry[1]);
    Read(fdarry[0]);
    wait(NULL);
    return 0;
}

运行结果

什么也没读出来，说明读端一直在阻塞等待。

1.2管道内数据被写满&&写端不关闭

同上，什么也读不出来，管道写满，写端阻塞等待。

1.3写端写了一部分，关闭写端

代码验证

#include<stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<unistd.h>
#include<string.h>
#include<sys/wait.h>

void Write(int fd)
{
    char buffer[128];
    int cnt = 0;
    while(1)
    {
        sprintf(buffer,"I am childProcess,I'm writing pid:%d cnt = %d\n",getpid(),cnt);
        write(fd,buffer,sizeof(buffer));
        if(cnt == 10)
        {
            break;
        }
        cnt++;
        sleep(1);
    }
    printf("close write\n");
    close(fd);
}

void Read(int fd)
{
    char buffer[1024];
    
    while(1)
    {   
        size_t n =  read(fd,buffer,sizeof(buffer)-1);
        if(n > 0)
        {
            printf("i am father process,I am reading\nmessage:%s\n",buffer);
        }
        else if(n == 0)
        {
            printf("read end\n");
            break;
        }
        else
        {
            printf("read error\n");
            break;
        }
    }

}


int main()
{
    int fdarry[2] = {0};
    int ret = pipe(fdarry);
    if(ret == -1)
    {
        printf("Create pipe fail\n");
        return -1;
    }

    pid_t pid = fork();

    if(pid == 0)
    {
        //子进程写
        close(fdarry[0]);
        Write(fdarry[1]);
        _exit(0);
    }

    close(fdarry[1]);
    Read(fdarry[0]);
    int status = 0;
    pid_t rid = waitpid(pid,&status,0);
    if(rid = pid)
    {
        printf("pid:%d exitsignal:%d exitcode:%d\n",rid,status&0x7f,WEXITSTATUS(status));
    }
    return 0;
}

运行结果