nbtest.c

Linux 设备驱动 Edition 3,书中的例题

/*
 * nbtest.c: read and write in non-blocking mode
 * This should run with any Unix
 *
 * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
 * Copyright (C) 2001 O'Reilly & Associates
 *
 * The source code in this file can be freely used, adapted,
 * and redistributed in source or binary form, so long as an
 * acknowledgment appears in derived source files.  The citation
 * should list that the code comes from the book "Linux Device
 * Drivers" by Alessandro Rubini and Jonathan Corbet, published
 * by O'Reilly & Associates.   No warranty is attached;
 * we cannot take responsibility for errors or fitness for use.
 */

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

char buffer[4096];

int main(int argc, char **argv)
{
	int delay = 1, n, m = 0;

	if (argc > 1)
		delay=atoi(argv[1]);
	fcntl(0, F_SETFL, fcntl(0,F_GETFL) | O_NONBLOCK); /* stdin */
	fcntl(1, F_SETFL, fcntl(1,F_GETFL) | O_NONBLOCK); /* stdout */

	while (1) {
		n = read(0, buffer, 4096);
		if (n >= 0)
			m = write(1, buffer, n);
		if ((n < 0 || m < 0) && (errno != EAGAIN))
			break;
		sleep(delay);
	}
	perror(n < 0 ? "stdin" : "stdout");
	exit(1);
}