Error reading %f and %e from a file in C

Question

In the following excerpt of my code I have to read a function of a txt file and extract its coefficients. When I set the coefficients as integers and read them with %d works correctly, but when placing the coefficients with floating point or even whole and reading with %f or %e the number that is read is a totally random number, as if it were garbage. I would like to know why this.

Reading this 1x1+2x2 this way it works. (nVar is the number of variables that the function is formed, this number is informed by a row of the file)

while(indice < nVar)
{                           
    fscanf(fp,"%d",&i);
    c1 = fgetc(fp);
    c2 = fgetc(fp);
    printf("%d%c%c; ",i,c1,c2);
    indice++;
}

but reading the function 1.5x1+2.3x2 or even 1x1+2x2 as follows the variables and their contents are read correctly, but for the coefficients a random number as garbage is read

while(indice < nVar)
{                           
    fscanf(fp,"%f",&x);
    c1 = fgetc(fp);
    c2 = fgetc(fp);
    printf("%f%c%c; ",x,c1,c2);
    indice++;
}

Answer 1

I can’t seem to reproduce your mistake.

That code

#include <stdio.h>

int main() {
    /* int i; */
    float x;
    char c1, c2;
    int ind = 0;
    while (ind < 2) {
        /* fscanf(stdin,"%d",&i); */
        fscanf(stdin,"%f",&x);
        c1 = fgetc(stdin);
        c2 = fgetc(stdin);
        printf("%f%c%c; ",x,c1,c2);
        ++ind;
    }
    return 0;
}

when I pass as input 1x1+2x2 prints:

/tmp . /a. out
1x1+2x2 1.000000x1; 2.000000x2; %

Already when I take the comment from the first fscanf and comment on the second, it prints:

/tmp . /a. out
1x1+2x2 1x1; 2x2; %

If you can give me an example of different input I can try to better understand the problem. :|

Putting the input into a file:

#include <stdio.h>

int main() {
    int i;
    char c1, c2;
    int ind = 0;
    float x;
    FILE *f = fopen("test.txt", "r");
    while (ind < 2) {
        /* fscanf(f,"%d",&i); */
        fscanf(f,"%f",&x);
        c1 = fgetc(f);
        c2 = fgetc(f);
        printf("%f%c%c; ",x,c1,c2);
        ++ind;
    }
    fclose(f);
    return 0;
}

The way out is exactly the same.