Why do I get Segmentation fault (core dumped)?

Question

I am a C beginner. After going through many tutorials I am not sure why am I getting the segmentation fault. I get this error on both my functions write_new_file and search_by_firstname. I think the problem lies within the argument type PERSON *inrecord in my function write_new_file. I have already tried changing it from a pointer to inrecord and changed all variables accordingly but the problem still existed. I have asked fellow class mates and no solution yet.

//------TYPEDEFS------
typedef struct{
    char firstname[20];
    char famname[20];
    char pers_number[13]; //yyyymmddnnnc
}PERSON;

void write_new_file(PERSON *inrecord){
    FILE *ptr_myfile;
    ptr_myfile=fopen("test.bin","w");
    if (ptr_myfile==NULL)
    {
        printf("Unable to open file!");
        exit(0);
    }
    strcpy(inrecord->firstname,"Name",20);
    strcpy(inrecord->famname, "surname",20);
    strncpy(inrecord->pers_number, "880192234",13);
    fwrite(&inrecord, sizeof(PERSON), 1, ptr_myfile);
    fclose(ptr_myfile);

}
void search_by_firstname(char *name){
    FILE *ptr_myfile;
    ptr_myfile=fopen("test.bin","r");
    PERSON *temp=NULL;
    if (ptr_myfile==NULL)
    {
        printf("Unable to open file!");
        exit(0);
    }

        fread(temp,sizeof(PERSON),1,ptr_myfile);
        if(strcmp(temp->firstname,name)!=0){
            printf("Not found");
            }else{
               printf("found");
            }

    fclose(ptr_myfile);
}

int main(void){
    PERSON *ppost=NULL;
    write_new_file(ppost);
    search_by_firstname("Neda");
    return(0);
}

Answer 1

1. You derefernce a NULL pointer, in

   void write_new_file(PERSON *inrecord)
   {
       FILE *ptr_myfile;
   
       ptr_myfile = fopen("test.bin","w");
       if (ptr_myfile == NULL)
       {
           printf("Unable to open file!");
           exit(0);
       }
       strcpy(inrecord->firstname, "Name", 20);
       strcpy(inrecord->famname, "surname", 20);
       strncpy(inrecord->pers_number, "880192234", 13);
       fwrite(&inrecord, sizeof(PERSON), 1, ptr_myfile);
       fclose(ptr_myfile);
   }
   

   you don't need to pass a pointer to the write file function, what you need is

   void write_new_file()
   {
       FILE *ptr_myfile;
       PERSON person;
   
       ptr_myfile = fopen("test.bin","w");
       if (ptr_myfile == NULL)
       {
           printf("Unable to open file!");
           exit(0);
       }
       strcpy(person.firstname, "Name", 20);
       strcpy(person.famname, "surname", 20);
       strncpy(person.pers_number, "880192234", 13);
   
       fwrite(&person, sizeof(PERSON), 1, ptr_myfile);
   
       fclose(ptr_myfile);
   }
   

   and in your main you would do this

   int main(void) {
       write_new_file();    
       search_by_firstname("Neda");
       return(0);
   }
   

2. You don't allocate space for temp, here you attempt to access temp

    fread(temp,sizeof(PERSON),1,ptr_myfile);
   

   but you didn't allocate space for it, you don't need pointer here either, instead

    PERSON temp;
    fread(&temp, sizeof(PERSON), 1, ptr_myfile);
   

   would do a better job, you might also want to check that you fread() succeeded, before trying to dereference temp because otherwise it will lead to undefined behavior.