Linux Application Development

Michael K. Johnson Erik W. Troan

mpx-nonblock.c

/* mpx-nonblock.c -- reads input from pipes p1, p2 using nonblocking i/o */

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

int main(void) {
    int fds[2];
    char buf[4096];
    int i;
    int fd;

    /* open both pipes in nonblocking mode */
    if ((fds[0] = open("p1", O_RDONLY | O_NONBLOCK)) < 0) {
        perror("open p1");
        return 1;
    }

    if ((fds[1] = open("p2", O_RDONLY | O_NONBLOCK)) < 0) {
        perror("open p2");
        return 1;
    }

    fd = 0;
    while (1) {
	/* if data is available read it and display it */
        i = read(fds[fd], buf, sizeof(buf) - 1);
        if ((i < 0) && (errno != EAGAIN)) {
            perror("read");
            return 1;
        } else if (i > 0) {
            buf[i] = '\0';
            printf("read: %s", buf);
        }

	/* read from the other file descriptor */
        fd = (fd + 1) % 2;
    }
}