Read floats from file

wsduvall · 03-10-2009, 09:53 AM

Hey guys.I've been working on this for quite some time, and I feel like I shouldn't be having this much trouble. I have a list of newline separated floats. The following code will read a float from a file "myfile.txt"

Code:

#include <stdio.h>

int main ()
{
  float f;
  FILE *fp;

  fp = fopen ("myfile.txt","r");
  fscanf (fp, "%f", &f);
  fclose (fp);
  printf ("I have read: %f\n",f);
  return 0;
}

What I cannot figure out how to do is make a loop which will read the list of floats into an array. Any help would be greatly appreciated!

wsduvall · 03-10-2009, 10:10 AM

Looks like I figured it out on my own. This code works:

Code:

#include <stdio.h>

int main ()
{
  int i;
  float f[100];
  FILE *fp;

  fp = fopen ("myfile.txt","r");
  for( i = 0; i < 50; i++ ) {
    if(fscanf (fp, "%f\n", &f[i]) !=1) {
      break;
    }
  }
  fclose (fp);
  printf ("I have read: %f and %f and %f\n",f[0],f[1],f[2]);
  return 0;
}

But there is one strange problem.

Code:

[wsduvall@Asar mpi]$ ./a.out 
I have read: 3.141600 and 23.120001 and 12.143000
[wsduvall@Asar mpi]$ cat myfile.txt
3.141600
23.12
12.143

Notice the difference between what the program is reading and what is actually in the file? It might have something to do with the precision... any ideas?

wsduvall · 03-10-2009, 10:18 AM

And I fixed that problem too... just changed float to double and all the %f's to %lf. Its only a shame I can't thank myself...