Programming

//parent.cpp
//Check for fork error
 if ( (pid = fork()) < 0 )
{
    cerr << "FORK ERROR" << endl;
    return -3;
}
else  if (pid == 0)  // Child 
{
    close(fd1[1]);//Close parent's stdout-write
    close(fd2[0]);//Close child's stdin-read
    if (fd1[0] != STDIN_FILENO)//Make sure file desc. matches
    {
        if (dup2(fd1[0], STDIN_FILENO) != STDIN_FILENO)
        {
            cerr << "dup2 error to stdin" << endl;
        }
        close(fd1[0]);
    }
    if (fd2[1] != STDOUT_FILENO)//Make sure file desc. mathces
    {
        if (dup2(fd2[1], STDOUT_FILENO) != STDOUT_FILENO)
        {
            cerr << "dup2 error to stdout" << endl;
        }
        close(fd2[1]);
    }
    if ( execl("./child", "child", (char *)0) < 0 )
    {
        cerr << "system error" << endl;
        return -4;
    }
    return 0;
}//end of child
else //parent
{
    int rv;
   close(fd1[0]);//Close parent's read
   close(fd2[1]);//close child's write
   if ( write(fd1[1], buffer, strlen(buffer)) != strlen(buffer))
    {
        cerr << "Write ERROR FROM PIPE" << endl;
    }
    if ( (rv = read(fd2[0], buffer, MAXLINE)) < 0 )
    {
        cerr << "READ ERROR FROM PIPE" << endl;
    }
    else if (rv == 0)
    {
        cerr << "Child Closed Pipe" << endl;
        return 0;
    }
    cout << "Output of child is: " << buffer;
    return 0;
}//end of parent

//child.cpp
char line[1000];
int MAXLEN=1001;    
read(STDIN_FILENO, line, MAXLEN);