How can I read separate numbers/lines from a .txt and input them to 2 different arrays

Question

I am trying to write a program that reads lines from a .txt and inputs them to 2 different arrays.

So far I have this:

    #include <stdio.h>

    int main() {
        FILE * ifp = fopen("input.txt","r"); 
        FILE * ofp = fopen ("output.txt", "w"); 
        int participants = 0, i;  
        char name [10];
        float grade [10];
        float perc [10];

        fscanf(ifp, "%d", &participants);

        for (i=1; i<participants; i++) {
             fscanf(ifp, "%s", &name);

             fscanf(ifp, "%f", &grade);

        }

        printf( "%d\n", participants);
        printf( "%s\n", name);
        printf( "%f\n", grade);

        fclose(ifp);
        fclose(ofp);

        return 0;
    }

The txt I'm trying to read is:

My problem is that it picks up the first 2 lines but stops when it gets to the numbers. I'm trying to get the names into an array and all the numbers, in pairs in a different array. Right now I'm just trying to check to see if I am picking up the numbers in the array but its not picking them all up.

This is the output that I get:

    2
    Optimus
    0.000000

Any ideas?

EDIT

This is my new code after some changes:

    #include <stdio.h>

    int main() {
        FILE * ifp = fopen("input.txt","r");
        FILE * ofp = fopen ("output.txt", "w");
        int participants = 0, i , j; 
       char name [10];
        int grade [26];
        float perc [26];

        fscanf(ifp, "%d", &participants);

        for (i=1; i<participants; i++) {
             fscanf(ifp, " %s", name);
             fscanf(ifp, " %d", grade);

        }

        printf( "%d\n", participants);
        printf( "%s\n", name);
        printf( "%d\n", grade[0]);

        fclose(ifp);
        fclose(ofp);

      return 0;
    }

And my new output is :

    2
    Optimus
    45

EDIT 2

What I need to do with those numbers later is divide the first number in a line with the second number in that same line, multiply it by 10, and then have it display "*" according to the number. So it would print out like this:

    Optimus
    +:  *****
    -:  *****
    *:  ********
    /:  *******
    Megatron
    +:  ********
    -:  *******
    *:  *******
    /:  ********

"+" is the first line under a name. "-" is the second line under that same name. "*" for the third. "/" for the fourth.

teppic · Accepted Answer · 2013-03-23 00:53:37Z

1

This is your main problem:

    printf( "%f\n", grade);

You're trying to print a pointer as a float. You want grade[0].

In this line:

    fscanf(ifp, "%f", &grade);

This will work, but it's not correct. It should be &grade[0] or just plain grade.

Of course in your final version, you'll need to adjust the array subscripts. You'll also need to allocate more arrays for the name - you currently can only store one.

To read in the data you will need to change the program a lot. You could declare grade as grade[10][8] (assuming a maximum of 10 participants), and store each of the 8 integers in the array. A loop like this would process it:

   for (i = 0; i < participants; i++) {
      fscanf(ifp, "%s", name);             // read the name (you need to fix this)
      for (j = 0; j < 8; j++) {
        fscanf(ifp, "%d", &grade[i][j]);   // store each number
      }
   }

edited Mar 23, 2013 at 0:53

answered Mar 23, 2013 at 0:04

teppic

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7 Comments

user1944441 Over a year ago

fscanf(ifp, "%f", &grade); is technically correct as well. As &grade == grade.

teppic Over a year ago

@Armin, it's not. &grade is a pointer to an array, not to an element.

user1944441 Over a year ago

Go try it and check the addresses of &grade and grade, it is the same.

Drieke Over a year ago

Ok, so I changed it and now it picks up the first number but stops there. How can I make it so that it continues to pick up the other numbers and when it gets to the name, it adds that to the "name" array.

teppic Over a year ago

@Armin, I'm quite aware of that, but they're not the same type.

|

suspectus · Accepted Answer · 2013-03-23 00:01:28Z

0

name and grade are arrays - the address of the variable is implicit for an array. So the address operator should not be used for these variables.

fscanf(ifp, "%s", name);
fscanf(ifp, "%f", grade);

answered Mar 23, 2013 at 0:01

suspectus

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