I'm trying to learn how to work with dynamic lists in C, but can't seem to wrap my head around it - so help would be appreaciated. I've got a struct that has some info that i'm reading from a txt file in the command line and would need to add the info to a dynamic list..
this is what i have so far. I'm at a loss with pointers and don't know if the arguments are correct and where to go from there.
Have spent the better part of the weekend looking for a way to get this done. It isn't hard as I get the concept, just that the nuts and bolts of it are just eluding me...
#include <stdio.h>
#include <stdlib.h>
#define SIZE_MAX 20
#define BUFFER_MAX 256
FILE *file;
/*struct*/
struct student {
char name[SIZE_MAX];
int grade;
struct student *next;
};
typedef struct student Student;
int addToList(Student **head, char *, int);
void printList(Student **head);
void releaseMem(Student **head);
/*functions*/
void addToList(Student **head, char *name, int grade ){
//???
}
/*Main*/
int main (int argc, char *argv[]){
Student *head=NULL,*tail=NULL;
int grade = 100 ;
char buffer [BUFFER_MAX];
char name[SIZE_MAX];
/*opening file*/
file = fopen(argv[1], "r");
if (file == NULL){
printf("\n\tWARNING: No data found.\n");
exit(1);
}
else{
printf("Reading file %s \n",argv[1]);
}
/*creating first node*/
Student* new_student(Student*)malloc(sizeof(Student));
while(fgets(buffer, BUFFER_MAX,file)!= NULL){
sscanf(buffer,"%s%d",name,&grade);
//printf("%s %d\n",string, grade);
addToList(&head,name,grade);
}
return 0;
}
Edit: So far I've managed to add the data from the file to a dynamic list (thank you for the help). Here is what I have:
#include <stdio.h>
#include <stdlib.h>
#define SIZE_MAX 20
#define BUFFER_MAX 256
FILE *file;
/*Struct*/
struct student {
char name[SIZE_MAX];
int grade;
struct student *next;
};
typedef struct student Student;
int addToList(Student **head, char *, int);
void printList(Student *head);
void releaseMem(Student *head);
/*functions*/
int addToList(Student **head, char *name, int grade ){
Student *new_student = malloc( sizeof( Student ) );
{
Student *new_student = malloc( sizeof( Student ) );
int success = new_student != NULL;
if ( success )
{
strcpy( new_student->name, name );
new_student->grade = grade;
new_student->next = *head;
*head = new_student;
}
return success;
}
}
void printList(Student *head){
Student * current = head;
int i = 1;
while (current != NULL) {
printf("%d. Student: %s grade %d\n",i,current->name ,current->grade);
i++;
current = current->next;
}
}
void releaseMem(Student *head){
Student * current = head;
while (current != NULL) {
free(current);
current = current->next;
}
printf("mem cleared.\n");
}
/*Main*/
int main (int argc, char *argv[]){
Student *head=NULL,*first=NULL, *temp = NULL;
int grade = 100 ;
char buffer [BUFFER_MAX];
char name[SIZE_MAX];
/*opening file*/
file = fopen(argv[1], "r");
if (file == NULL){
printf("\n\tWARNING: No data found.\n");
exit(1);
}
else{
printf("reading file %s. \n",argv[1]);
}
printf("data added to list.\n");
while(fgets(buffer, BUFFER_MAX,file)!= NULL){
sscanf(buffer,"%s%d",name,&grade);
addToList(&head,name,grade);
}
printList(head);
releaseMem(head);
return 0;
}
Works (almost) like i'd like it to work. For some reason the printList function prints the content of the file in reverse order and after fiddling with it for some time I don't know how to print it from the beginning to the end instead from the end to the beginning. I suppose it has to do with pointers but more than that i'm at a loss what to do... What am I missing here? How would I go about reversing the printing order with keeping the (formatting) as it currently is?
