Linux process communication of documents

Parent and child share files using open file descriptors ------ completion of inter-process communication.

/*** 
 fork_share_fd.c
 ***/
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/wait.h>


int main(void)
{
    int fd1, fd2; pid_t pid;
    char buf[1024];
    char *str = "---------test for shared fd in parent child process-----\n";


    pid = fork();
    if (pid < 0) {
        perror("fork error");
        exit(1);
    } else if (pid == 0) {
        fd1 = open("test.txt", O_RDWR);
        if (fd1 < 0) {
            perror("open error");
            exit(1);
        }
        write(fd1, str, strlen(str));
        printf("child wrote over...\n");

    } else{ 
        FD2 = Open ( " test.txt " , O_RDWR);
         IF (FD2 < 0 ) { 
            perror ( " Open error " ); 
            Exit ( . 1 ); 
        } 
        SLEEP ( . 1 );                    // ensure that the child process writes data 

        int len Read = (FD2, buf, the sizeof (buf)); 
        Write (STDOUT_FILENO, buf, len); 

        the wait (NULL); 
    } 

    return  0 ; 
}

operation result:

ubuntu1604 @ ubuntu: ~ / wangqinghe / linux / 20190806 $ ./fork_share_fd

child wrote over...

---------test for shared fd in parent child process-----