fifo2.c

《Beginning Linux Programming》书的配置实例源代码。

// Let's start with the header files, a #define and the check that the correct number
// of command-line arguments have been supplied.

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>

#define FIFO_NAME "/tmp/my_fifo"

int main(int argc, char *argv[])
{
    int res;
    int open_mode = 0;
    int i;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s <some combination of\
               O_RDONLY O_WRONLY O_NONBLOCK>\n", *argv);
        exit(EXIT_FAILURE);
    }

// Assuming that the program passed the test, we now set the value of open_mode
// from those arguments.

    for(i = 1; i < argc; i++) {
        if (strncmp(*++argv, "O_RDONLY", 8) == 0)
             open_mode |= O_RDONLY;
        if (strncmp(*argv, "O_WRONLY", 8) == 0)
             open_mode |= O_WRONLY;
        if (strncmp(*argv, "O_NONBLOCK", 10) == 0)
             open_mode |= O_NONBLOCK;
     }

// We now check whether the FIFO exists and create it if necessary.
// Then the FIFO is opened and output given to that effect while the program
// catches forty winks. Last of all, the FIFO is closed.

    if (access(FIFO_NAME, F_OK) == -1) {
        res = mkfifo(FIFO_NAME, 0777);
        if (res != 0) {
            fprintf(stderr, "Could not create fifo %s\n", FIFO_NAME);
            exit(EXIT_FAILURE);
        }
    }

    printf("Process %d opening FIFO\n", getpid());
    res = open(FIFO_NAME, open_mode);
    printf("Process %d result %d\n", getpid(), res);
    sleep(5);
    if (res != -1) (void)close(res);
    printf("Process %d finished\n", getpid());
    exit(EXIT_SUCCESS);
}