Write to file descriptor and immediately read from it

Question

Today I have encountered some weird looking code that at first glance it's not apparent to me what it does.

  send(file_desc,"Input \'y\' to continue.\t",0x18,0);
  read(file_desc,buffer,100);
  iVar1 = strcmp("y",(char *)buffer);
  if (iVar1 == 0) {
    // some more code
  }

It seems that a text string is being written into the file descriptor. Immediately then after that it reads from that file descriptor into a buffer. And it compares if the text written into the buffer is a "y".

My understanding (please correct me if I am wrong), is that it writes some data which is a text string into the file descriptor, and then the file descriptor acts as a temporary storage location for anything you write to it. And after that it reads that data from the file descriptor into the buffer. It actually is the same file descriptor. It seems as a primitive way of using a file descriptor to copy data from the text string into the buffer. Why not just use a strcpy() instead?

What would be the use case of writing to a file descriptor and then immediately read from it? It seems like a convoluted way to copy data using file descriptors. Or maybe I don't understand this code well enough, what this sequence of a send() and a read() does?

And assuming that this code is instead using the file descriptor to copy the text string "Input \'y\' to continue.\t" into the buffer, why are they comparing it with the string "y"? It should probably be false every single time.

I am assuming that any data written into a file descriptor stays in that file descriptor until it is read from. So here it seems that send() is being used to write the string into, and read() is used to read it back out.

In man send it says:

 The only difference between send() and write(2) is the presence of flags.  With a zero
       flags argument, send() is equivalent to write(2).

why would they use send() instead of write()? This code is just so mind boggling.

---

Edit: here's the full function where this code is originally from:

void send_read(int file_desc)

{
  int are_equal;
  undefined2 buffer [8];
  char local_28 [32];

                    /* 0x6e == 110 == 'n' */
  buffer[0] = 0x6e;
  send(file_desc,"Input \'y\' to continue.\t",0x18,0);
  read(file_desc,buffer,100);
  are_equal = strcmp("y",(char *)buffer);
  if (are_equal == 0) {
    FUN_00400a86(file_desc,local_28);
  }
  else {
    close(file_desc);
  }
  return;
}

Answer 1

The send() and recv() functions are for use with sockets (send: send a message on a socket — recv: receive a message from a connected socket). See also the POSIX description of Sockets in general.

Socket file descriptors are bi-directional — you can read and write on them. You can't read what you wrote, unlike with pipe file descriptors. With pipes, the process writing to the write end of a pipe can read what it wrote from the read end of the pipe — if another process didn't read it first. When a process writes on a socket, that information goes to the peer process and cannot be read by the writer.