FIFO例子

###################    fifo.h  #################

#ifndef FIFO_H
#define FIFO_H

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define SERVER_FIFO "fifo_server"
#define FIFOMODE (O_CREAT | O_RDWR | O_NONBLOCK | S_IRUSR | S_IWUSR)
#define UMASK 0

struct simple_message {
    pid_t sm_clientpid;
    char sm_data[100];
};
#endif


###############   server.c        #####################
#include "fifo.h"

int main()
{
    int fd_server, fd_client, fd_server_w=-1, i;
    ssize_t nread;
    struct simple_message msg;
    char fifo_name[100];

    printf("server started\n");
    if (mkfifo(SERVER_FIFO, UMASK | FIFOMODE)==-1 && errno!=EEXIST) {
        perror("make fifo error\n");
        exit(0);
    }
    
    if ((fd_server = open(SERVER_FIFO, O_RDONLY)) < 0) {
        perror("open error\n");
        exit(1);
    }
    if ((fd_server_w = open(SERVER_FIFO, O_WRONLY)) < 0) {
        perror("open error\n");
        exit(1);
    }   

    while(1) {
        if ((nread = read(fd_server, &msg, sizeof(msg))) < 0) {
            perror("read error\n");
            exit(2);
        }
        for (i=0; msg.sm_data[i] != '\0'; i++)
            msg.sm_data[i] = toupper(msg.sm_data[i]);
        snprintf(fifo_name, sizeof(fifo_name), "fifo%ld", (long)msg.sm_clientpid);
        if ((fd_client = open(fifo_name, O_WRONLY)) < 0) {
            perror("open error\n");
            exit(1);
        }
        if (write(fd_client, &msg, sizeof(msg)) < 0) {
            perror("write error");
            exit(1);
        }
        if (close(fd_client) < 0) {
            perror("close error\n");
            exit(1);
        }
    }
    if (close(fd_client) < 0 || close(fd_server_w) < 0) {
        perror("close error\n");
        exit(1);
    }

    return 0;
}


###############      client.c   #################################3
#include "fifo.h"

int main()
{
    int fd_server, fd_client = -1, i, fd_client_w=-1;
    ssize_t nread;
    struct simple_message msg;
    char fifo_name[100];
    char *work[] = {
        "appleasauce",
        "tiger",
        "mountain",
        NULL
    };

    printf("client %ld started\n", (long)getpid());

    msg.sm_clientpid = getpid();
    snprintf(fifo_name, sizeof(fifo_name), "fifo%ld", (long)msg.sm_clientpid);
    if (mkfifo(fifo_name, UMASK | FIFOMODE)==-1 && errno != EEXIST) {
        perror("make fifo error\n");
        exit(0);
    }
    if ((fd_server = open(SERVER_FIFO, O_WRONLY)) < 0) {
        perror("open error\n");
        exit(1);
    }

    for (i=0; work[i]!=NULL; i++) {
        strcpy(msg.sm_data, work[i]);
        if (write(fd_server, &msg, sizeof(msg)) < 0) {
            perror("write error\n");
            exit(1);
        }
        if (fd_client == -1) {
            if ((fd_client = open(fifo_name, O_RDONLY)) < 0) {
                perror("open error\n");
                exit(1);
            }
        }
        if (fd_client_w == -1) {
            if ((fd_client_w = open(fifo_name, O_WRONLY)) < 0) {
                perror("open error\n");
                exit(1);
            }
        }
        if ((nread = read(fd_client, &msg, sizeof(msg))) < 0) {
            perror("read error\n");
            exit(1);
        }
        printf("client %ld: %s ----> %s\n", (long)getpid(), work[i], msg.sm_data);
    }
    if (close(fd_server)<0 || close(fd_client_w)<0 || close(fd_client)<0 || unlink(fifo_name)<0) {
        perror("close error\n");
        exit(1);
    }
    printf("Client %ld done\n", (long)getpid());

    return 0;
}