Segmentation Fault when printf string from a textfile

Hi! I have a struct

Code:

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struct Human {
  char *name;
  int age;
};

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I am trying to save and then read from textfile. I am doing this:

Code:

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struct Human human= {"Carl",30};
printf("%s", human.name);



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... Then I am saving it using

Code:

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fwrite(&human, sizeof(Human), 1, outfile);

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I am getting a resut as I am expecting and the printf works fine.
However, If I load from file using similar fread(). Then do the same printf, then I get the segmetation fault! Also This happens surely because of the string, not the integer, integers still gest outputted correctly if I get rid of string output.
Thank you!

The problem is that fwrite writes the struct object member-wise, so if it has a pointer member, it writes the value of the pointer, i.e., an address, not what the pointer points to. You could change the pointer to char to be an array of char, but then you would be limited by the array size. If you want to keep it as a pointer, then you would be better off writing to file in a different way, e.g., a text format (or later I would recommend SQLite).

Change your structure to

Code:

---

struct Human {
  char name[30];
  int age;
};

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Pointers have to be dealt with separately when it comes to reading and writing to files.

Code:

---

struct Human {
  char *name;
  int age;
};

struct Human human= {"Carl",30};

// save
size_t len = strlen(human.name);
fwrite(&len, sizeof(len), 1, outfile);  // the length of the name
fwrite(human.name, len, 1, outfile); // the name, excluding the \0
fwrite(&human.age, sizeof(human.age), 1, outfile); // the age


// load
size_t len;
fread(&len, sizeof(len), 1, infile);  // the length of the name
human.name = malloc(len+1);  // make space for the chars, and a \0
fread(human.name, len, 1, infile); // the name, excluding the \0
human.name[len] = '\0';
fread(&human.age, sizeof(human.age), 1, infile); // the age

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Serialization - Wikipedia is the rabbit hole to go down if you want more.