list.c

#include <stdio.h>
#include <stdlib.h>

struct element{
  struct element *prev;
  struct element *next;
  char *text;

};
  typedef struct element linked_list;


linked_list empty_linked_list(){

  linked_list kopf  = {NULL,NULL,NULL};//malloc(sizeof(linked_list));
  return kopf;
}

int append(linked_list *liste,char* text){

 linked_list *ele = malloc(sizeof(linked_list));
  if(ele != NULL){
    ele->text = text;

    if(liste->next == NULL){//liste = leer
      liste->prev = ele;
      liste->next = ele;
      //return 1;
    }else{
      liste->prev = ele; //letzte element
      ele->prev = liste;//letzte element in der Liste
      //return 11;
    }
    return 1;
  }else{
    return 0;
  }
}

void worka(char* t){
  printf("%s\n",t);
}

void visit_all(linked_list *liste, void (*work)(char* t)){

  while(liste->next != NULL){
    work(liste->text);
    //printf("%s\n",liste->text);
    liste = liste->next;
  }

}

int main(){

  linked_list li = empty_linked_list();

  char *bla = "hallo";
  char *bla2 = "Welt";

  printf("%d\n", append(&li,bla));
  printf("%d\n", append(&li,bla));
  // printf("%d\n", insert(&li,bla2,2));
   visit_all(&li,&worka);

  return 0;
}