pipe管道

pipe()学习

例1: 进程内读写管道,代码如下:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <signal.h>

int main(int argc, char *argv[])
{
    int fd[2];

    pipe(fd);
    char s[100] = "hello pipe....";

    while(1)
    {
        write(fd[1],s,100);
        bzero(s,100);
        read(fd[0],s,100);
        puts(s);
        sleep(1);
    }
    
    return 0;
}

编译/链接执行后的结果如下:

例2: 进程间读写管道,代码如下:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <signal.h>
void child_rw_pipe(int rfd,int wfd)
{
    char msg[] = "from child process!!!\n";
    write(wfd,msg,sizeof(msg));

    char msg2[100];
    read(rfd,msg2,100);
    printf("child read from pipe:  %s\n",msg2);
}

void parent_rw_pipe(int rfd,int wfd)
{
    char msg[] = "from parent process!!!\n";
    write(wfd,msg,sizeof(msg));

    char msg2[100];
    read(rfd,msg2,100);
    printf("parent read from pipe:  %s\n",msg2);
}


int main(int argc, char *argv[])
{
    int fd1[2];
    int fd2[2];

    pipe(fd1);
    pipe(fd2);

    pid_t pid = fork();
    if(pid == 0)
    {
        close(fd1[1]);
        close(fd2[0]);
        child_rw_pipe(fd1[0],fd2[1]);
        exit(0);
    }

    close(fd1[0]);
    close(fd2[1]);
    parent_rw_pipe(fd2[0],fd1[1]);
    wait(NULL);

    return 0;
}

 

父子进程分别向管道写数据, 从管道读数据. 编译/链接/执行,结果如下:

 

例3: 父子进程间读写管道:

父进程将命令行数据写入管道, 代码如下:

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include <termios.h>
#include <signal.h>
int main(int argc,char *argv[])
{
    int fd[2];
    pid_t pid;
    
    pipe(fd);
    pid = fork();
    if(pid == 0)
    {
        close(fd[1]);        
        close(0);
        dup(fd[0]);
        
        execl("process","process",NULL);
        exit(0);
    }

    close(fd[0]);  
    write(fd[1],argv[1],strlen(argv[1]));  
    wait(NULL);

    return 0;
}

子进程读出管道内容(前面代码dup(fd[0])将文件描述符STDIN_FILENO重定向到管道的读端), 代码如下:

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include <termios.h>
#include <signal.h>
int main(int argc,char *argv[])
{
    while(1)
    {
        char buf[100];
        int ret = read(STDIN_FILENO,buf,100);
        if(ret > 0)
        {
            buf[ret] = 0;
            printf("process receive:  %s\n",buf);
            if(strcmp(buf,"exit") == 0)
                exit(0);
            if(strcmp(buf,"getpid") == 0)
            {
                printf("child pid = %d\n",getpid());
                exit(0);
            }
        }
    }

    return 0;
}

编译/链接/执行, 结果如下: