FILE *fp; 12 char s[128]; 13 char s1[128]={1,2,3}; 14 if (argc<2) 15 { 16 printf("canshu is error \n"); 17 return -1; 18 19 } 20 if((fp= fopen(argv[1],"a"))==NULL) 21 { 22 perror("fopen"); 23 return -1; 24 } 25 if(fwrite(s1,sizeof(char),128,fp)<0L) 26 { 27 perror("fwrite"); 28 return -1; 29 } 30 if(fseek(fp,0,SEEK_SET)<0) 31 { 32 perror("fseek"); 33 return -1; 34 } 35 36 if(fread(s,sizeof(char),128,fp)<0) 37 { 38 perror("fread"); 39 return -1; 40 } 41 puts(s); 42 printf("-----------------\n"); 43 puts(s1); 44 return 0; 45 } ~ 为啥还是打印不出来

这段代码中，打印不出来的原因可能是因为文件指针在写入数据后没有正确地定位到文件开头，或者读取的数据长度不够。可以在代码中加入以下语句来进行检查：

1. 检查文件指针是否在写入后正确地定位到文件开头：

long cur_pos = ftell(fp);
if (cur_pos != 0) {
    perror("ftell");
    return -1;
}

这样可以获取当前文件指针的位置，如果不是0，则说明文件指针没有正确地定位到文件开头。

2. 检查读取的数据是否够128个字节：

size_t read_bytes = fread(s, sizeof(char), 128, fp);
if (read_bytes < 128) {
    perror("fread");
    return -1;
}

这样可以获取实际读取的字节数，如果不够128个字节，则说明读取失败。

在加入上述代码后，可以检查一下输出的错误信息，以确定具体的问题所在。

相关问题

重新编写s0.c,s1.c,s2.c的代码

以下是 `s0.c`, `s1.c` 和 `s2.c` 的重新编写版本，保持原有功能的同时，进行了适当的优化和注释：

### s0.c: 初始状态设置进程

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define SEM_FILE "sem_name.tmp"
#define EMPTY_FILE "empty.txt"
#define CLIENT_FILE "pvh"
#define FULL_FILE "full.txt"

void sigint_handler(int);

int semid;
struct sembuf psembuf, vsembuf;

int main(int argc, char *argv[]) {
    int k = 10, buffer = 1;
    char filename[20];
    FILE *fempty, *full, *fp[k];
    key_t key;
    short initarray[3];

    signal(SIGINT, sigint_handler);

    // 创建并打开SEM_FILE
    fempty = fopen(SEM_FILE, "w");
    if (fempty == NULL) {
        perror("Error opening SEM_FILE for writing");
        return 1;
    }

    // 生成键值
    key = ftok(SEM_FILE, 'a');
    printf("Key = %u\n", key);
    if (key == -1) {
        perror("Error generating key");
        return 1;
    }

    // 获取信号量集
    semid = semget(key, 3, 0777 | IPC_CREAT);
    printf("Semaphore ID = %d\n", semid);
    if (semid == -1) {
        perror("Error getting semaphore");
        return 1;
    }

    // 初始化信号量
    initarray[0] = buffer;   // 缓冲池
    initarray[1] = k;        // 空缓冲区
    initarray[2] = 0;        // 满缓冲区
    if (semctl(semid, 0, SETALL, initarray) == -1) {
        perror("Error initializing semaphores");
        return 1;
    }

    // 验证初始化
    short outarray[3];
    if (semctl(semid, 0, GETALL, outarray) == -1) {
        perror("Error getting semaphore values");
        return 1;
    }
    printf("Semaphore initial values: %d, %d, %d\n", outarray[0], outarray[1], outarray[2]);

    // 关闭SEM_FILE
    fclose(fempty);

    // 创建EMPTY_FILE和FULL_FILE
    fempty = fopen(EMPTY_FILE, "w");
    full = fopen(FULL_FILE, "w");

    if (fempty == NULL || full == NULL) {
        perror("Error opening files for writing");
        return 1;
    }

    // 创建k个空文件并将文件名写入EMPTY_FILE
    for (int i = 0; i < k; i++) {
        sprintf(filename, "%s%03d.txt", CLIENT_FILE, i);
        fp[i] = fopen(filename, "w");
        if (fp[i] == NULL) {
            perror("Error creating client file");
            return 1;
        }
        fclose(fp[i]);
        fprintf(fempty, "%s\n", filename);
    }

    fclose(full);
    fclose(fempty);

    // 再次验证信号量值
    if (semctl(semid, 0, GETALL, outarray) == -1) {
        perror("Error getting semaphore values");
        return 1;
    }
    printf("Semaphore values: %d, %d, %d\n", outarray[0], outarray[1], outarray[2]);

    getchar();
    return 0;
}

void sigint_handler(int sig) {
    if (semctl(semid, 0, IPC_RMID, 0) == -1) {
        perror("Error removing semaphore");
    }
    exit(0);
}

### s1.c: 写者进程

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define SEM_FILE "sem_name.tmp"
#define EMPTY_FILE "empty.txt"
#define FULL_FILE "full.txt"

int semid;
unsigned int count;
struct sembuf psembuf[2], vsembuf[2];

typedef struct {
    char str[100];
    char num[6];
} Msg;

int main(int argc, char *argv[]) {
    int k = 10, area = 0, first = 1, second = 2;
    char emptyname[20], restname[k * 20];
    FILE *fempty, *full;
    key_t key;
    short outarray[3];
    Msg msg;

    // 初始化
    memset(emptyname, 0x00, 20);
    memset(restname, 0x00, k * 20);
    memset(msg.str, 0x00, sizeof(msg.str));
    memset(msg.num, 0x00, sizeof(msg.num));

    // 生成键值
    key = ftok(SEM_FILE, 'a');
    printf("Key = %u\n", key);
    if (key == -1) {
        perror("Error generating key");
        return 1;
    }

    // 获取信号量集
    semid = semget(key, 3, 0777);
    printf("Semaphore ID = %d\n", semid);
    if (semid == -1) {
        perror("Error getting semaphore");
        return 1;
    }

    // 设置P操作和V操作
    psembuf[0].sem_op = -1;
    psembuf[0].sem_flg = SEM_UNDO;
    vsembuf[0].sem_op = 1;
    vsembuf[0].sem_flg = SEM_UNDO;

    psembuf[1].sem_op = -1;
    psembuf[1].sem_flg = SEM_UNDO;
    vsembuf[1].sem_op = 1;
    vsembuf[1].sem_flg = SEM_UNDO;

    // 验证初始化
    if (semctl(semid, 0, GETALL, outarray) == -1) {
        perror("Error getting semaphore values");
        return 1;
    }
    printf("Semaphore initial values: %d, %d, %d\n", outarray[0], outarray[1], outarray[2]);

    for (count = 0;; count++) {
        psembuf[0].sem_num = area;
        psembuf[1].sem_num = first;

        // P操作
        if (semop(semid, psembuf, 2) == -1) {
            perror("Error in P operation");
            return 1;
        }

        // 验证信号量值
        if (semctl(semid, 0, GETALL, outarray) == -1) {
            perror("Error getting semaphore values");
            return 1;
        }
        printf("After P, semaphore values: %d, %d, %d\n", outarray[0], outarray[1], outarray[2]);

        // 读取EMPTY_FILE中的空缓冲区名称
        fempty = fopen(EMPTY_FILE, "r");
        full = fopen(FULL_FILE, "a");
        fread(emptyname, sizeof(char), 10, fempty);
        fwrite(emptyname, strlen(emptyname), sizeof(char), full);
        fclose(full);

        int i = 0;
        while (!feof(fempty)) {
            fread(restname + i * 10, sizeof(char), 10, fempty);
            i++;
        }
        printf("Rest restname: (%s)\n", restname);
        fclose(fempty);

        // 更新EMPTY_FILE
        fempty = fopen(EMPTY_FILE, "w");
        fwrite(restname, strlen(restname), sizeof(char), fempty);
        fclose(fempty);

        memset(restname, 0x00, sizeof(restname));

        // 构建消息
        sprintf(msg.str, "Hello, I am Writer_ pid: %d, msg_no: %d", getpid(), count);
        sprintf(msg.num, "%03d", 0); // 假设初始读者数量为0

        // 写入空缓冲区
        fempty = fopen(emptyname, "w");
        fwrite(msg.str, strlen(msg.str), sizeof(char), fempty);
        fwrite(msg.num, strlen(msg.num), sizeof(char), fempty);
        fclose(fempty);

        printf("%s\n", msg.str);
        printf("%s\n", msg.num);

        // 验证信号量值
        if (semctl(semid, 0, GETALL, outarray) == -1) {
            perror("Error getting semaphore values");
            return 1;
        }
        printf("Semaphore values: %d, %d, %d\n", outarray[0], outarray[1], outarray[2]);

        // 如果满缓冲区计数为0，唤醒读者
        if (outarray[2] == 0) {
            vsembuf[1].sem_num = second;
            vsembuf[0].sem_num = area;
            if (semop(semid, vsembuf, 2) == -1) {
                perror("Error in V operation");
                return 1;
            }
            if (semctl(semid, 0, GETALL, outarray) == -1) {
                perror("Error getting semaphore values");
                return 1;
            }
            printf("After V area and reader, semaphore values: %d, %d, %d\n", outarray[0], outarray[1], outarray[2]);
        } else {
            vsembuf[0].sem_num = area;
            if (semop(semid, vsembuf, 1) == -1) {
                perror("Error in V operation");
                return 1;
            }
            if (semctl(semid, 0, GETALL, outarray) == -1) {
                perror("Error getting semaphore values");
                return 1;
            }
            printf("After V area, semaphore values: %d, %d, %d\n", outarray[0], outarray[1], outarray[2]);
        }
    }

    return 0;
}

### s2.c: 读者进程

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define SEM_FILE "sem_name.tmp"
#define EMPTY_FILE "empty.txt"
#define FULL_FILE "full.txt"
#define MAX_MSG_NUM 10000

int semid;
unsigned int count;
struct sembuf psembuf[2], vsembuf[2];

typedef struct {
    char str[100];
    char num[6];
} Msg;

int main(int argc, char *argv[]) {
    int k = 10, n = 2, area = 0, first = 2, second = 1, msg_no = 0, readers = n, receive_msg_no = 0, has_read = 0, empty_add_num = 0;
    int Read = 0;
    char emptyname[20], restname[k * 20];
    FILE *fempty, *full, *fp;
    key_t key;
    Msg msg;
    char receive_msg[MAX_MSG_NUM][100];
    short outarray[3];

    // 初始化
    memset(emptyname, 0x00, 20);
    memset(restname, 0x00, k * 20);
    memset(msg.str, 0x00, sizeof(msg.str));
    memset(msg.num, 0x00, sizeof(msg.num));
    for (int i = 0; i < MAX_MSG_NUM; i++)
        memset(receive_msg[i], 0x00, 100);

    // 生成键值
    key = ftok(SEM_FILE, 'a');
    printf("Key = %u\n", key);
    if (key == -1) {
        perror("Error generating key");
        return 1;
    }

    // 获取信号量集
    semid = semget(key, 3, 0777);
    printf("Semaphore ID = %d\n", semid);
    if (semid == -1) {
        perror("Error getting semaphore");
        return 1;
    }

    // 设置P操作和V操作
    psembuf[0].sem_op = -1;
    psembuf[0].sem_flg = SEM_UNDO;
    vsembuf[0].sem_op = 1;
    vsembuf[0].sem_flg = SEM_UNDO;

    psembuf[1].sem_op = -1;
    psembuf[1].sem_flg = SEM_UNDO;
    vsembuf[1].sem_op = 1;
    vsembuf[1].sem_flg = SEM_UNDO;

    // 验证初始化
    if (semctl(semid, 0, GETALL, outarray) == -1) {
        perror("Error getting semaphore values");
        return 1;
    }
    printf("Semaphore initial values: %d, %d, %d\n", outarray[0], outarray[1], outarray[2]);

    for (count = 0;; count++) {
        empty_add_num = 0;
        printf("Count = %d, Receive message number = %d\n", count, receive_msg_no);

        psembuf[0].sem_num = area;
        psembuf[1].sem_num = first;

        // P操作
        if (semop(semid, psembuf, 2) == -1) {
            perror("Error in P operation");
            return 1;
        }

        // 验证信号量值
        if (semctl(semid, 0, GETALL, outarray) == -1) {
            perror("Error getting semaphore values");
            return 1;
        }
        printf("After P, semaphore values: %d, %d, %d\n", outarray[0], outarray[1], outarray[2]);

        // 读取FULL_FILE中的满缓冲区名称
        full = fopen(FULL_FILE, "r");
        if (full == NULL) {
            perror("Error opening full file");
            return 1;
        }

        int i = 0;
        memset(restname, 0x00, k * 20);
        size_t bytesRead = fread(restname, sizeof(char), 10, full);

        while (bytesRead > 0) {
            has_read = 0;
            fp = fopen(restname, "r");
            if (fp == NULL) {
                perror("Error opening temp file");
                continue;
            }

            fgets(msg.str, 100, fp);
            fgets(msg.num, 10, fp);

            printf("File: %s, Message: %s\n", restname, msg.str);
            printf("File: %s, Number: %s\n", restname, msg.num);

            for (int j = 0; j < receive_msg_no && !has_read; j++) {
                if (strcmp(receive_msg[j], msg.str) == 0) {
                    printf("The message has been read!\n");
                    has_read = 1;
                }
            }

            if (has_read) {
                memset(restname, 0x00, k * 20);
                bytesRead = fread(restname, sizeof(char), 10, full);
                fclose(fp);
                continue;
            } else {
                strcpy(receive_msg[(receive_msg_no++) % MAX_MSG_NUM], msg.str);
            }

            printf("Message number: %d\n", atoi(msg.num));

            if (atoi(msg.num) == 2495) {
                empty_add_num++;
                printf("I am the last reader for file: %s, I will empty it and add its name to file: %s!\n", restname, EMPTY_FILE);
                printf("%s\n", msg.str);
                printf("%s\n", msg.num);

                fclose(fp);
                fp = fopen(restname, "w");
                if (fp == NULL) {
                    perror("Error opening temp file for writing");
                    continue;
                }
                fclose(fempty);
                fempty = fopen(EMPTY_FILE, "a");
                if (fempty == NULL) {
                    perror("Error opening empty file for appending");
                    continue;
                }
                fwrite(restname, strlen(restname), sizeof(char), fempty);
                fclose(fempty);

                memset(restname, 0x00, k * 20);
                i = 0;
                bytesRead = fread(restname + i * 10, sizeof(char), 10, full);
                while (bytesRead > 0) {
                    i++;
                    bytesRead = fread(restname + i * 10, sizeof(char), 10, full);
                }
                printf("Rest restname: (%s)\n", restname);

                fclose(full);
                full = fopen(FULL_FILE, "w");
                if (full == NULL) {
                    perror("Error opening full file for writing");
                    continue;
                }
                fwrite(restname, strlen(restname),