fprintf 有问题

Question

我正在尝试编写一个模拟反病毒扫描的代码，它扫描 5 个特定文件，然后创建一个名为 AntiVirusLog.txt 的文件。在此文件中，它会写入结果，例如PSY.avi INFECTED。受感染文件是包含文件youtubesign 中的字符串的文件。

我的问题是，当我尝试将结果打印到文件 AntiVirusLog.txt 时，它不会打印任何内容并将文件留空。

我的代码：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<dirent.h>
#define BUZZ_SIZE 1024
int fast_scan(char *fname, char *str, FILE *fs);
int slow_scan(char *fname, char *str, FILE *fs);
int main(int argc, char *argv[])
{
    char name[100];
    char choice[5];
    char buff[BUZZ_SIZE];
    FILE *f7, *f2;
    struct dirent *de;
    DIR *dr = opendir(argv[1]);
    if (dr == NULL)  // opendir returns NULL if couldn't open directory
    {
        printf("Could not open current directory");
        return 0;
    }
    f2 = fopen(argv[2], "rb");
    f7 = fopen("AntiVirusLog.txt", "wt");
    printf("Welcome to Amnon's Anti-Virus program\n which scan would you like to choose?:\n");
    printf("Fast: check only the first and the last 20% of the file\n Slow: Checks the entire file\n");
    printf("Enter fast for a fast scan and slow for a slow scan\n");
    scanf("%s", choice);
    if ((strcmp(choice, "slow"))==0)
    {
        while ((de = readdir(dr)) != NULL)
        {
            strcpy(name, argv[1]);
            strcat(name, de->d_name);
            if((fgets(buff, BUZZ_SIZE, f2)) != NULL)
            {
                slow_scan(name, buff, f7);
            }
        }
    }
    if ((strcmp(choice, "fast")) == 0)
    {
        while ((de = readdir(dr)) != NULL)
        {
            strcpy(name, argv[1]);
            strcat(name, de->d_name);
            if ((fgets(buff, BUZZ_SIZE, f2)) != NULL)
            {
                fast_scan(name, buff, f7);
            }
        }
    }
    printf("The scan was made successfuly, check the file AntiVirusLog.txt to see the results\n");
    closedir(dr);
    fclose(f2);
    fclose(f7);
    system("PAUSE");
    return (0);
}
int slow_scan(char *fname, char *str, FILE *fs)
{
    int findres = 0;
    FILE *fp;
    char temp[BUZZ_SIZE];
    if ((fopen_s(&fp, fname, "rb")) != NULL)
    {
        return(-1);
    }
    while ((fgets(temp, BUZZ_SIZE, fp)) != NULL)
    {
        if ((strstr(temp, str)) != NULL)
        {
            fprintf(fs, "%s INFECTED\n", fname);
            findres++;
        }
    }
    if (findres==0)
    {
        fprintf(fs, "%s NOT INFECTED\n", fname);
    }
    fclose(fp);
    return(0);
}
int fast_scan(char *fname, char *str, FILE *fs)
{
    int findres=0;
    int i, j, len, partlen;
    FILE *fp;
    if ((fopen_s(&fp, fname, "rb")) != NULL)
    {
        return(-1);
    }
    fseek(fp, 0, SEEK_END);
    len = ftell(fp);
    partlen = (len * 20) / 100;
    char *temp=malloc(partlen);
    while ((fgets(temp, BUZZ_SIZE, fp)) != NULL)
    {
        for (i = 0; i < partlen; i++)
        {
            if (temp[i]=str[i])
            {
                findres++;
            }
            if (temp[i] != str[i])
            {
                i = partlen + 1;
            }
            if (findres == partlen)
            {
                fprintf(fs, "%s INFECTED\n", fname);
                i = partlen + 1;
            }
        }
        for (j = len - partlen; j < len; j++)
        {
            if (temp[j] = str[j])
            {
                findres++;
            }
            if (temp[j] != str[j])
            {
                j = partlen + 1;
            }
            if (findres == partlen)
            {
                fprintf(fs, "%s INFECTED\n", fname);
                j = partlen + 1;
            }
        }
    }
    if (findres!= partlen)
    {
        fprintf(fs, "%s NOT INFECTED\n", fname);
    }
    fclose(fp);
    return(0);
}

Answer 1

我听了一些建议，并找到了自己的一些修复方法，现在它可以完美运行了！更新后的代码如下所示：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define BUZZ_SIZE 1024
int search_sign(char *fname, char *str, FILE *fs);
int main(int argc, char *argv[])
{
    char buff[BUZZ_SIZE];
    FILE *f,*f7;
    f7 = fopen("AntiVirusLog.txt", "wt");
    f = fopen(argv[1], "rb");
    if ((fgets(buff, BUZZ_SIZE, f)) != NULL)
    {
        search_sign(argv[2], buff, f7);
        search_sign(argv[3], buff, f7);
        search_sign(argv[4], buff, f7);
        search_sign(argv[5], buff, f7);
        search_sign(argv[6], buff, f7);
    }
    printf("The scan was made successfuly, check the file AntiVirusLog.txt to see the results\n");
    fclose(f);
    fclose(f7);
    system("PAUSE");
    return (0);
}
int search_sign(char *fname, char *str, FILE *fs)
{
    int findres = 0;
    FILE *fp;
    char temp[BUZZ_SIZE];
    if ((fopen_s(&fp, fname, "rb")) != NULL)
    {
        return(-1);
    }
    while ((fgets(temp, BUZZ_SIZE, fp)) != NULL)
    {
        if ((strstr(temp, str)) != NULL)
        {
            fprintf(fs, "%s INFECTED\n", fname);
            findres++;
        }
    }
    if (findres==0)
    {
        fprintf(fs, "%s NOT INFECTED\n", fname);
    }
    fclose(fp);
    return(0);
}

Answer 2

您的代码主要有两个主要问题

• 第 1 点：在您的代码中，对于类似的一系列调用

   search_sign(argv[1], buff, f7);
  

  您正在使用未初始化的buff。然后将buff 作为search_sign() 的第二个参数（被接受为str）传递，该参数再次用作strstr() 中的搜索字符串。

  由于buff 是一个自动 局部变量，初始内容（值）是垃圾（不确定），因此，当用作strstr() 中的搜索键时，将调用undefined behaviour .

• 第 2 点：也就是说，as my previous comment，在进一步使用返回的文件指针之前，您应该始终检查 fopen() 调用是否成功。