how do I read a long list of data from a file?

I am practicing C with a periodic table project. I have this .txt file that contains all the elements in this order:
atomic_number name symbol mass_number.

My program was supposed to populate an array of structures with the data (for easy searching).
The problem is my program doesn't go all the way to the last element (atomic_number = 118) it just stops at 54 and doesn't print further. It also does not populate the array beyond 54.

Here is how I have tried to tackle the problem

file: populate.c

#include "periodic_table.h"

int populate(void)
{
    struct element
    {
        int atomic_num;
        char name[15];
        char symbol[5];
        float mass_num;
    };

    // Array to hold the elements
    struct element e[118];

    // checks that the file exists
    FILE *ptr = fopen("periodic_table.txt", "r");
    if (ptr == NULL)
    {
        printf("No file to read from.\nExiting...\n");
        return 1;
    }

    int line;   // first line of the txt file
    for (line = 1; line <= 118; line++)
    {
        if (fscanf(ptr, "%d %s %s %f", &e
.atomic_num, &e
.name, &e
.symbol, &e
.mass_num))
        {
            //print is just for debugging purpose
            printf("%d record: %d %s %s %.2f\n", line, e
.atomic_num, e
.name, e
.symbol, e
.mass_num);
        }
        fflush(stdin);
    }

    fclose(ptr);
    return (0);
}

My text file looks like this

1 Hydrogen H 1.01
2 Helium He 4.00
3 Lithium Li 6.94
.
.
.
116 Livermorium Lv 293.00
117 Tennesine Ts 294.00
118 Oganesson Og 294.00

There are multiple problems in your program:

• the definition for struct element and the array e is local to the populate function, so the data will be unavailable once the function returns.

• the index variable line should run from 0 to 117 as it is used to index the e[118] array. accessing e[118] has undefined behavior.

• you should read one line at a time and use sscanf() to parse the line, and report conversion errors along with the line contents for easier debugging.

• the test if (fscanf(...)) is incorrect: the return value should be 4 if all 4 conversions succeeded. any other result should be considered an error.

• %s is a risky conversion specifier as fscanf() can cause a buffer overflow if the file contents has words longer than expected.

• you should not use & for destination variables that are arrays.

• fflush(stdin); is useless and actually has undefined behavior.

Here is a modified version:

#include "periodic_table.h"

// these definitions should be moved to "periodic_table.h"
struct element {
    int atomic_num;
    char name[15];
    char symbol[5];
    float mass_num;
};

// Array to hold the elements
struct element e[118];

int populate(void) {
    // checks that the file exists
    FILE *ptr = fopen("periodic_table.txt", "r");
    if (ptr == NULL) {
        fprintf(stderr, "No file to read from.\nExiting...\n");
        return 1;
    }

    int line;   // first line of the txt file
    for (line = 0; line < 118; line++) {
        char buffer[128];
        int pos;
        if (!fgets(buffer, sizeof buffer, ptr)) {
            fprintf(stderr, "cannot read element %d\n", line + 1);
            break;
        }
        if (sscanf(buffer, "%d%14s%4s%f%n", &e
.atomic_num, e
.name,
                   e
.symbol, &e
.mass_num, &pos) == 4) {
            //print is just for debugging purpose
            printf("%d record: %d %s %s %.2f\n",
                   line + 1, e
.atomic_num, e
.name,
                   e
.symbol, e
.mass_num);
            if (buffer[pos] != '\n') {
                fprintf(stderr, "line %d: extra data: %s\n", line + 1, buffer + pos);
            }
        } else {
            fprintf(stderr, "line %d: invalid data: %s\n", line + 1, buffer);
        }
    }

    fclose(ptr);
    return 0;
}