Reading lines from a text file in C

Question

This question already has answers here: question from:https://stackoverflow.com/questions/65947165/reading-lines-from-a-text-file-in-c

Answer 1

You can use fscanf to read in floating point numbers directly, without the need to call atof. Assuming you have a file called numbers.txt with the content:

3.14159
2.877
91.3
-1392.22
0.1234

The following program will read them in and store them in an array of floats. Take care though, the array is only large enough to hold 5 numbers. If you need a variable amount of numbers, then you must dynamically allocate an array to hold them.

#include <stdio.h>
#include <string.h>

int main(void) {
    int i = 0;
    float numbers[5] = {0};

    FILE *fp = fopen("numbers.txt", "rb");
    if (!fp) {
        puts("could not open file");
        return 1;
    }

    for (;;) {
        if (fscanf(fp, "%f
", &numbers[i]) != 1) {
            break;
        }
        i++;
    }

    fclose(fp);
    return 0;
}