Creating Doubly Linked List from text file on C

You want int and not int * in your data structure, and the temperature should be a float or double rather than an int (which greatly simplifies the input; otherwise, handling both 26.09 and 26.9 correctly is rather hard when you use two integers to input the temperature).

typedef struct tempdata tempdata;

struct tempdata
{
    int       hour;
    int       min;
    float     temp;
    tempdata *next;
    tempdata *prev;
};

Your header would be more convincing without the typo:

typedef struct templist templist;

struct templist
{
    tempdata *head;
    tempdata *tail;
    int size;
} templist;

Having an array of tempdata structures is actually more sensible than a doubly linked list, but it defeats the object of the exercise, I fear. You should probably be dynamically allocating the structures as you need them. I'd use fgets() plus sscanf(), but you are checking the result from fscanf() — which is good — but you could get stuck if the data is malformed because the file is not at EOF but doesn't contain a digit where fscanf() needs one. You should be checking that the return value is 3 (one for each converted field), and if not, breaking the loop.

To create a list, you will need a variable of type templist somewhere, appropriately initialized.

I've assembled the program below from your outline. Given the data file:

12:29 26.34
13:32 28.23
14:20 28.56
15:30 29.10
16:18 30.45
17:20 28.12
18:20 26.98
19:35 24.12

The output I got was:

Data: 12:29  26.34
Data: 13:32  28.23
Data: 14:20  28.56
Data: 15:30  29.10
Data: 16:18  30.45
Data: 17:20  28.12
Data: 18:20  26.98
Data: 19:35  24.12

Data entry complete:
Head: 0x102800BB0, Tail: 0x102800C90, Size: 8
Temp: 0x102800BB0: 12:29  26.34
Temp: 0x102800BD0: 13:32  28.23
Temp: 0x102800BF0: 14:20  28.56
Temp: 0x102800C10: 15:30  29.10
Temp: 0x102800C30: 16:18  30.45
Temp: 0x102800C50: 17:20  28.12
Temp: 0x102800C70: 18:20  26.98
Temp: 0x102800C90: 19:35  24.12

Code

#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct tempdata tempdata;

struct tempdata
{
    int       hour;
    int       min;
    float     temp;
    tempdata *next;
    tempdata *prev;
};

typedef struct templist templist;

struct templist
{
    tempdata *head;
    tempdata *tail;
    int size;
};

static void add_to_list(templist *list, tempdata *new_temp)
{
    assert(list != 0);
    assert(list->size >= 0);
    assert((list->head == 0 && list->tail == 0 && list->size == 0) ||
           (list->head != 0 && list->tail != 0 && list->size != 0));
    new_temp->prev = list->tail;
    new_temp->next = 0;
    list->size++;
    if (list->head == 0)
        list->head = new_temp;          /* New list */
    else
        list->tail->next = new_temp;    /* Add to tail of list */
    list->tail = new_temp;
}

static void print_temp(const tempdata *data)
{
    printf("%d:%d %6.2f\n", data->hour, data->min, data->temp);
}

static void print_list(const templist *list)
{
    const tempdata *data;
    assert(list != 0);
    assert(list->size >= 0);
    assert((list->head == 0 && list->tail == 0 && list->size == 0) ||
           (list->head != 0 && list->tail != 0 && list->size != 0));
    printf("Head: 0x%" PRIXPTR ", Tail: 0x%" PRIXPTR ", Size: %d\n",
            (uintptr_t)list->head, (uintptr_t)list->tail, list->size);
    for (data = list->head; data != 0; data = data->next)
    {
        printf("Temp: 0x%" PRIXPTR ": ", (uintptr_t)data);
        print_temp(data);
    }
}

int main(int argc, char **argv)
{
    FILE *ifp;
    templist list = { NULL, NULL, 0 };
    char line[2048];

    if (argc != 2)
    {
        fprintf(stderr, "Usage: %s filename\n", argv[0]);
        return(EXIT_FAILURE);
    }

    ifp = fopen(argv[1], "r");

    if (ifp == 0)
    {
        fprintf(stderr, "%s: could not open file %s (%d: %s)\n", argv[0], argv[1], errno, strerror(errno));
        return(EXIT_FAILURE);
    }

    while (fgets(line, sizeof(line), ifp) != 0)
    {
        tempdata  temp_val;
        tempdata *new_temp;

        if (sscanf(line, "%d:%d %f", &temp_val.hour, &temp_val.min, &temp_val.temp) != 3)
        {
            fprintf(stderr, "%s: failed to scan line - %s", argv[0], line);
            return(EXIT_FAILURE);
        }
        printf("Data: ");
        print_temp(&temp_val);
        if ((new_temp = malloc(sizeof(*new_temp))) == 0)
        {
            fprintf(stderr, "%s: failed to allocate memory (%zu bytes)\n", argv[0], sizeof(*new_temp));
            return(EXIT_FAILURE);
        }
        new_temp->hour = temp_val.hour;
        new_temp->min  = temp_val.min;
        new_temp->temp = temp_val.temp;
        new_temp->next = 0;
        new_temp->prev = 0;
        add_to_list(&list, new_temp);
        /*print_list(&list);*/
    }
    fclose(ifp);

    printf("\nData entry complete:\n");

    print_list(&list);
    return(EXIT_SUCCESS);
}