MPs queue: the parent process sends messages to the child process!

MPs queue: the parent process sends messages to the child process! -- Linux general technology-Linux programming and kernel information. The following is a detailed description. # Include
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Int main (int argc, char * argv [])
{
Int pfd [2];
Pid_t cpid;
Char buf;
Pipe (pfd); // Create an MPs queue
Cpid = fork (); // create a process
If (cpid = 0)
{
Close (pfd [1]); // close the Write file descriptor
While (read (pfd [0], & buf, 1)> 0) // read
Write (STDOUT_FILENO, & buf, 1 );
Write (STDOUT_FILENO, "\ n", 1 );
Close (pfd [0]);
Exit (0 );
}
Else if (cpid> 0)
{
Close (pfd [0]);
Write (pfd [1], argv [1], strlen (argv [1]);
Close (pfd [1]);
Wait (NULL );
Exit (0 );
}
Return 0;
}

Input:./pipetest abc
Output: abc
Question: After creating a child process, it is generally because the child process starts to execute (cpid = 0), but the parent process has not been written yet. if the while process in the child process ends, it exits first, after the parent process is executed, no results will be output because the child process has exited. why?