Demonstrating a Posix pipe writer being full and not being emptied

pipe_write_full.c

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>

#define PIPE_MAX (1 << 16)

int main() {
	int pipefd[2];
	
	if (pipe(pipefd) == -1) {
		perror("Pipe cannot be acquired");
		exit(EXIT_FAILURE);
	}

	int flags = fcntl(pipefd[1], F_GETFL, 0);
	if (flags == -1) {
		perror("File flags cannot be obtained");
		exit(EXIT_FAILURE);
	}
	if (fcntl(pipefd[1], F_SETFL, flags | O_NONBLOCK) == -1) {
		perror("File flags cannot be set");
		exit(EXIT_FAILURE);
	}

	char buffer[PIPE_MAX + 1];
	memset(buffer, 'x', PIPE_MAX + 1);

	int write_res = write(pipefd[1], buffer, PIPE_MAX + 1);
	printf("Written %d out of %d\n", write_res, PIPE_MAX + 1);
	// -> Written 65536 out of 65537

	int read_res = read(pipefd[0], buffer, 16);
	printf("Read %d\n", read_res);
	// -> Read 16

	int write_new_res = write(pipefd[1], buffer, 8);
	printf("Written %d out of %d\n", write_new_res, 8);
	// -> Written -1 out of 8
}