Inputing a special text file into linked list and trying to print

Question

I'm trying to create a C program to read and input the available information from a file called records.txt into a linked list and trying to print it as a simple test, but I'm not sure where the program went wrong since it's not inputting or printing anything at all. Any suggestions would be extremely helpful.

records.txt goes by: data code(int), state(string), town name(string), population(int), area(float), longitude(float), latitude(float), travel code(int), and travel distance(float)

// The lines from records.txt file to input:

2564273NYKirby                                                 57      0.108676 43.803003-108.180310 6344  3.3662
7483946WYNewville                                            2085      2.435594 30.659203 -93.89685227591  0.9094
6394057HKickersville                                          520      1.963467 39.958220 -82.59599812626  0.2182
9174015ILWorkland Springs                                    1166      1.125451 42.091306 -88.850345 9110  7.4211
2373597NCFunland                                              579      8.390613 34.301093 -77.78746720394  3.5175
9533594WAKirkland                                           45054     10.675565 47.685821-122.191729  386  0.3655
7183994INHappy Mines                                          766      0.323048 40.193940 -86.36009213178  4.7952
0194152IAMoonville                                             76      0.285352 41.728980 -95.26655811596  5.1724

// The C Program so far:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <dlfcn.h>
#include <unistd.h>

// places record
typedef struct records{
    char state[2], name[30];
    int code, popul, interCode;
    float area, latit, longit, interDist;
} records;

// linked list with places record
typedef struct node{
    records data;
    struct node *next;
} node, *list;

// insert a record into list
void insert_list (list *L, records data) {
    node *p;
    
    // get a free node
    p = (node *) malloc (sizeof (node));
    
    // put the record in it
    p->data = data;
    
    // link it to the first node in the list
    p->next = *L;
    
    // make the first node equal to this one
    // (so now the former first, p->next, is the second)
    *L = p;
}

// create an empty list
void create_list (list *L) {
    *L = NULL;
}

// main program
int main () {
    list data;    // data list of records.txt
    records r, *p = NULL;
    FILE * fin;
    
    // open the file if possible otherwise error displayed
    fin = fopen ("records.txt", "r");
    if (!fin) {
        perror ("records.txt");
        exit (1);
    }
    
    // make an empty list
    create_list (&data);
    
    // read records, inserting them into the list
    while (1) {
        fscanf (fin, "%d %s %s %d %f %f %f %d %f",
                &r.code, r.state, r.name, &r.popul,
                &r.area, &r.latit, &r.longit, &r.interCode, &r.interDist);
        
        // if reached end of file get out of loop
        if (feof (fin)) break;
        insert_list (&data, r);
        
        // test print
        printf ("%d %s %s %d %f %f %f %d %f\n", p->code, p->state, p->name, p->popul,
                p->area, p->latit, p->longit, p->interCode, p->interDist);
    }
    fclose (fin);
    exit (0);
}

Answer 1

A major problem is that e.g. %s reads space-delimited "words". If you have e.g. NYKirby then that will be read as a single word.

Another major problem is that %s writes null-terminated byte strings to your arrays. And you need to reserve space for the null-terminator. A string of length 2 needs space for 3 characters.

The first problem can be solved by using field-width specifiers, like e.g. %2s to read only two characters.

The second problem can be solved by increasing the size of your arrays.

There's also a third problem, which is that you don't check what fscanf returns. You need to do this to check for errors.

---

This leaves you with the problem of reading strings containing space in them, like Workland Springs.

A potential way to solve it is to use the %[] format instead, to specify that only letters and spaces could be read by fscanf. Perhaps like %29[A-Za-z ]. It will however also read the trailing spaces after the name, which you then need to strip.