C：“写：管道损坏”错误

Question

I want to try Pipe communication with child and parent process. Parent process write to pipe and child process read this but my program get error "write: Broken pipe". How can I change this code? Thnks.

#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <termios.h>
#include <errno.h>
#include <fcntl.h>


int main(void)
{
    int i=0;
    int child=5;
    int fdp;
    int fds[2];
    int controlRead;
    int controlWrite;
    char pathName[30] = {"Trying Pipe Communication\n"};


    if(pipe(fds) < 0)
    {
        perror("pipe");
        exit(EXIT_FAILURE);
    }

    do{

        if(child == 0)
        {
            close(fds[1]);
            if( (controlRead = read(fds[0],pathName,sizeof(pathName)) ) <= 0)
            {
                perror("read");
                exit(EXIT_FAILURE);
            }
            close(fds[0]);

            printf("boru :%s\n",pathName);
            wait();
        }
        else
        {

            printf("Parent process\n");
            close(fds[0]);
            if( (controlWrite = write(fds[1],&pathName,sizeof(pathName))) <= 0)
            {
                perror("write");
                exit(EXIT_FAILURE);
            }
            close(fds[1]);


        }
        i++;
        child = fork();
    }while(i<3);

    return 0;
}

Answer 1

error "write: Broken pipe". How can I change this code?

Don't break the pipe before you write to it. On the first pass through your do/while loop, the parent closes the read end and then writes to the remaining pipe fd. Kablam. EPIPE.

Answer 2

Your read loop shall count number of bytes read before closing the socket. Otherwise it is terminated too early.

Pipes are not packet transport, and single read/write is actually a series of operations. So when you are writing an array, it is wrong to assume it will come in one piece.