检查文件是否包含来自另一个文件 C 的内容

Question

所以我正在做一个项目，我需要检查某个文件是否包含另一个文件的内容。
我在 c 中创建了一个函数（它不是 c++）来尝试它，但它似乎进入了一个无限循环并且无法整体工作，我尝试使用 Visual Studio 调试器，但它没有给我更多信息。

注意：我包括stdlib.h

代码：

int findFileInFile(const char* wherePath, const char* whatPath)
{
    FILE* fpBigger = fopen(wherePath, "r");
    FILE* fpSmaller = fopen(whatPath, "r");

    if (fpBigger != NULL && fpSmaller != NULL)
    {
        unsigned char cs = 0;
        unsigned char cb = 0;

        while ((cb = fgetc(fpBigger)) != EOF)
        {
            cs = fgetc(fpSmaller);

            if (cs == EOF)
                return 1;

            if (cs != cb)
            {
                fseek(fpSmaller, 0L, SEEK_SET);
            }
        }

        return 0;
    }
    else
    {
        printf("File names are wrong!\n");
        exit(-1);
    }
}

谢谢。

Answer 1

我想这就是你要找的东西：

#include <stdio.h>
#include <stdlib.h>
int findFileInFile(const char *wherePath, const char *whatPath)
{
  FILE *fpBigger = fopen(wherePath, "rb");
  FILE *fpSmaller = fopen(whatPath, "rb");

  if (fpBigger != NULL && fpSmaller != NULL)
  {
    unsigned char cs = 0;
    unsigned char cb = 0;
    int s;
    int b;
    while (1)
    {
      b = fgetc(fpBigger);
      s = fgetc(fpSmaller);
      if (s == EOF && b == EOF) //if both return values from fgetc are EOF, it means you've reached the end of the file which wouldn't have been possible if both of the files weren't equal
      {
        return 1;
      }
      else if (s == EOF || b == EOF)
      {
        return 0;
      }
      cs=(unsigned char)s; //casting the int to unsigned char
      cb=(unsigned char)b; //casting the int to unsigned char
      if (cs != cb) //compare the characters gotten from the files, if not equal, return 0
      {
        return 0;
      }
    }
  }
  else
  {
    printf("File names are wrong!\n");
    exit(-1);
  }
}
int main()
{
  printf("%d", findFileInFile("file1.txt", "file2.txt"));
}

最后但并非最不重要的一点是，您还可以使用feof() 检查是否已到达文件流的末尾。

编辑：（这可能不是最佳解决方案，但它会检查较大的文件是否包含较小的文件）

#include <stdio.h>
#include <stdlib.h>
int findFileInFile(const char *wherePath, const char *whatPath)
{
  FILE *fpBigger = fopen(wherePath, "rb");
  FILE *fpSmaller = fopen(whatPath, "rb");

    unsigned char cs = 0;
    unsigned char cb = 0;
    int s;
    int b;
    int loc;
    if (fpBigger != NULL && fpSmaller != NULL)
    {
      s = fgetc(fpSmaller);
      cs=(unsigned char)s;
      while((b=fgetc(fpBigger))!=EOF){ //checks for the first instance of the first character of the smaller file in the bigger file
        cb=(unsigned char)b;
        if(cs==cb){
            loc=ftell(fpBigger)-1; //set loc to the position where the first character of the smaller file is found in the bigger file
            break;
        }
      }
      if(b==EOF){ //if the character is not found, return 0
          return 0;
      }
      fseek(fpBigger,loc,SEEK_SET);
      rewind(fpSmaller);
      while((b=fgetc(fpBigger))!=EOF){
          if((s=fgetc(fpSmaller))==EOF){ //check if the end of smaller file is reached, and return 1 if true
              return 1;
          }
          cs=(unsigned char)s;
          cb=(unsigned char)b;
          if(cs!=cb){
              rewind(fpSmaller); //if the characters gotten from both the files are not equal, go to the very beginning of smaller file
              loc++; //increase the position to start the search from in the bigger file by 1
              fseek(fpBigger,loc,SEEK_SET);
          }
      }
      if(b==EOF&&fgetc(fpSmaller)==EOF){
        return 1;
      }
      return 0;
    }
  else
  {
    printf("File names are wrong!\n");
    exit(-1);
  }
}
int main()
{
  printf("%d", findFileInFile("file1.txt", "file2.txt"));
}