How to read space-separated values in C?

Question

I have a .txt file that I am using to learn some basic C.

Here is the txt file:

8
12  48  15  65  16  82  9   72

Here is my C program:

#include <stdio.h>
#include <stdlib.h>



int main(int argc, char** argv){

        char num = 0;
        //int[] arr = 0;


        if (argc != 2){
                return 0;
        }

        FILE *inputFile = fopen(argv[1], "r");

        if (inputFile == NULL){
                printf("Error1\n");
                return 0;
        }

        while(!feof(inputFile)){
                num = fgetc(inputFile);
                printf("%c\n",num);
        }

        if(!feof(inputFile)){
                printf("error");
                return 0;
        }

}

My goal is the get an array of the second line, based on the amount of values in the first line.... essentially, we want an array with 8 values, that stores {12, 48, ....}

Please see [Why is “while ( !feof (file) )” always wrong?](http://stackoverflow.com/questions/5431941/why-is-while-feof-file-always-wrong), and `char num` should be `int num`. Blame your tutor. — Weather Vane, Oct 01 '17 at 20:56
Use `fscanf` with `malloc`. like [this](https://ideone.com/KKK4dd) — BLUEPIXY, Oct 01 '17 at 20:59

score 4 · Accepted Answer · answered Oct 01 '17 at 21:01

You are using a wrong function to read integers: in spite of returning an int, function fgetc is reading individual characters (why getchar returns an int?).

In order to read space-separated integers, use fscanf instead, and check the return value to decide that you have reached the end of file:

int n;
while (fscanf(inputFile, " %d", &n) == 1) {
    printf("%d\n", n);
}

Note that the loop above avoids using feof to detect the end of file condition (why using feof is wrong?)

score 1 · Answer 2 · answered Oct 01 '17 at 21:02

If you aim to read a series of numbers (and nothing else), regardless of the number of line breaks in between, you could simply use fscanf as follows:

    int num;
    while(fscanf(inputFile, "%d", &num) == 1) {
            printf("%d\n",num);
    }

Note that fscanf returns the number of values successfully read in according to the format specifier, i.e. it returns 1 as long as an integral value could have been read in (and 0 otherwise).

How to read space-separated values in C?

2 Answers2