warning: more '%' conversions than data arguments

I'm new to C and I'm trying to write a program as an assignment. The user should input 7 floats which will then be stored in an array.

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

int main() {
  float data[32];
  printf("Instert 7 values, separated by spaces: ");
  scanf("%f %f %f %f %f %f %f", data);

  return 0;
}

And I keep getting the error

warning: more '%' conversions than data arguments [-Wformat]
scanf("%f %f %f %f %f %f %f", data);

I tried to look for a solution online but I couldn't figure it out, what am I doing wrong?

3 answers

  • answered 2018-11-08 00:14 Yastanub

    It tells you what is wrong it is just unfortunate that your variable name matches the error messages words. scanf wants a variable for every % there is in the format string. That means in yout example it expects 7 variables but only gets 1.

  • answered 2018-11-08 00:16 Swordfish

    You could use a loop:

    for (int i = 0; i < 7; ++i)
        scanf("%f", &data[i]);
    

    With error detection:

    #include <stdio.h>
    #include <stdlib.h>
    
    // ...
    
    int num_values_read = 0;
    for (; num_values_read < 7 && scanf("%f", &data[num_values_read]) == 1;
         ++num_values_read);
    
    if (num_values_read != 7) {
        fputs("Input error :(\n\n", stderr);
        return EXIT_FAILURE;
    }
    

  • answered 2018-11-08 00:16 Judismar Arpini Junior

    This

    scanf("%f %f %f %f %f %f %f", data);
    

    should be like this

    scanf("%f %f %f %f %f %f %f", &data[0], &data[1], &data[2], &data[3], &data[4], &data[5], &data[6]);
    

    The scanf function requires, for each %-something on the initial string, a pointer to a variable where you'll be storing the input value.

    You could alternatively write like this:

    scanf("%f %f %f %f %f %f %f", data, data+1, data+2, data+3, data+4, data+5, data+6);
    

    Your array's base memory address/pointer is data. When you sum it with an i where i is a positive integer, you get the pointer to the ith position in the array.