Fwrite（）结构数组到c中的文件

Question

fwrite() does not match input from array of structs.

Tried: binary files, printing fields of struct elements prior to fwrite.

FILE *currentPartition;

    struct FAT {
    char *filename;
    int file_length;
    int blockPtrs[10];
    int current_location;       
    } fat[20];`

    for (int i=0;i<20;i++)
     {
      printf("Appending fat index: %d\n",i);
      printf("filename: %s\n",fat[i].filename);
      printf("file length: %d\n",fat[i].file_length);

      printf("current location: %d\n",fat[i].current_location);

      fwrite(fat,sizeof(struct FAT),1,currentPartition);}

When I later fread, this code does not return what i originally fwrote into the file.

Answer 1

Your struct contains a pointer to filename , which is an address of data allocated at the time or write. You did not write the string which represents the name, just the pointer to it.

When you read it, your program would read the same pointer, but where does it point to? There is probably no string, or it is at a completely different address. So, you need to make sure that the string is written. The easiest way is to have a char filename[LEN]; as your struct field, where LEN is a big enough number. Otherwise, you need to write the string separately and then restore it as a separate entity.