c - How to malloc linked list node while reading file -

i've posted question similar this, able further narrow down issue. i'm pretty sure know problem is, i've been stuck figuring out how solve it.

//assuming typedef struct person person;   struct person{      char first_n[100];      char last_n[100];       char middle_n[100];      struct person* next; };   void open_file_and_read(char* file){      file* fp = fopen(file_name, "r");      if (fp != null){          while (!feof(fp)){                person* person = malloc(sizeof(person));                person->next = null;                while (fscanf(fp, "%s %s %s", person->first_n, person->last_n, person->middle_n) == 3){                    add_to_contacts(person);                }          }       } }    void open_write_file(char* file){     file* filep = fopen(file, "w");     person* copy;     (copy = front; copy != null; copy=copy->next){             fprintf(filep, "%s %s %s\n", copy->last_n, copy->first_n, copy->middle_n);     }     fclose(filep); 

}

void add_to_contacts(person* person){     printf("last_name: %s", person->last_name);     if (head == null){         person->next = head;         head = person;     else{         person->next = head;         head = person;     } }   int main(int argc, char * argv[]) { char* inputfilename = argv[1]; if (inputfilename == null){     inputfilename = "myrolodex"; } open_read_file(inputfilename); char command; while (command != 'q' && command != 'q'){     printf("starting read command\n");     command = read_command(inputfilename);     evaluate_command(command); } open_write_file(inputfilename);  clear_rolodex(); 

the printf prints out in file 1 node. ex: file contains:
bob lee steve
mike steven noel first, last, middle
james nguyen lee

the printf prints out leestevennguyen. these should separate.

i believe problem has malloc being called once, when need called each time scanf. can't move person* person = malloc(sizeof(person)); under while...fscanf loop because fscanf dependent on having person created. how go mallocing each new person. similar assignment due in couple of hours , i've spent last 10 hours trying work , believe big part.

thank you

edit more detail: have print statement in add_to_contacts function prints out node->lasts_name. added print statement before sorting function(not posted) , prints infinitely

there several ways resolve this.

the 1 think directly matches want is:

               person* person = malloc(sizeof(person));                person->next = null;                while (fscanf(fp, "%s %s %s", person->first_n, person->last_n, person->middle_n) == 3){                    add_to_contacts(person);                    person = malloc(sizeof(person));                    person->next = null;                }                free(person); 

this assumes add_to_contacts inserts malloc'd pointer data structure, need next fscanf put data in different location.

having done this, there 1 person* allocated @ end not ever passed add_to_contacts, can , should free pointer when loop exits.

a slight variation is

               person* person = malloc(sizeof(person));                while (fscanf(fp, "%s %s %s", person->first_n, person->last_n, person->middle_n) == 3){                    person->next = null;                    add_to_contacts(person);                    person = malloc(sizeof(person));                }                free(person); 

(the idea there thing needs person->next = null; here presumably add_to_contacts(person), , postponing person->next = null; until last moment don't have call outside loop inside loop.)

an alternative (quite different) approach declare local variables, let fscanf write them, , copy them newly allocated person inside loop.

a third approach make person stack-allocated (not malloc'd) variable, , make add_to_contacts make own malloc'd copy of in order insert copy in data structure.

but these last 2 options involve fscanf writing data 1 place , having copy in order put in larger structure. seems may want avoid copy.