comparing floats in two structs - c

Question

I have a code that reads two .txt files and puts them into structs. Then, I want to compare the x value from each file and find matches. The type of these values is floats. I keep getting incorrect matches and line numbers and I'm not sure what to do. It works for the first few but then it just says there's a match when it is only a value in one file. Everything else works fine, so if anyone has suggestions on comparing the values that would be much appreciated. Thank you.
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
#define FLT_EPSILON 1.19209290E-07F
typedef struct fcat_s {
float x;
float y;
float a_j2000;
float b_j2000;
float mag;
} fcat_s;
typedef struct cat_s {
float num;
float x;
float y;
float xworld;
float yworld;
float flux_auto;
float mag_auto;
float awin;
float bwin;
} cat_s;
int main(void) {
float exptime = 0;
float F = 0;
float Mi = 0;
float Mcat = 0;
float FLUX_AUTO = 0;
float ZP = 0;
char fcatname[50];
char catname[50];
int fcatcount = 0;
int catcount = 0;
char fcat_c;
char cat_c;
float x;
char str[100];
int i = 0;
int j = 0;
float temp;
int match = 0;
printf("Please input the .fcat file name:\n");
scanf("%str", fcatname);
printf("Please input the .cat file name:\n");
scanf("%str", catname);
printf("Please input the exposure time:\n");
scanf("%f", &exptime);
fcat_s *f = (fcat_s *)malloc(sizeof(fcat_s));
cat_s *c = (cat_s *)malloc(sizeof(cat_s));
// .fcat file
FILE *fcat;
fcat = fopen(fcatname, "r");
if (fcat == NULL) {
printf("The input file does not exist\n");
} else {
for (fcat_c = getc(fcat); fcat_c != EOF; fcat_c = getc(fcat)) {
if (fcat_c == '\n')
fcatcount++;
if (fcatcount > 4) {
fscanf(fcat, "%f", &f[fcatcount-5].x);
fscanf(fcat, "%f", &f[fcatcount-5].y);
fscanf(fcat, "%f", &f[fcatcount-5].a_j2000);
fscanf(fcat, "%f", &f[fcatcount-5].b_j2000);
fscanf(fcat, "%f", &f[fcatcount-5].mag);
}
}
}
printf("\n");
printf("The .fcat file has %d lines. \n", fcatcount);
printf("\n");
printf("\n");
printf("FCAT CONTENTS\n");
for (i = 0; i < (fcatcount-5); i++) {
printf("%lf\t %lf\t %lf\t %lf\t %lf\n",
f[i].x, f[i].y, f[i].a_j2000, f[i].b_j2000, f[i].mag);
}
printf("\n");
printf("\n");
// .cat file
FILE *cat;
cat = fopen(catname, "r");
if (cat == NULL) {
printf("The input file does not exist\n");
} else {
for (cat_c = getc(cat); cat_c != EOF; cat_c = getc(cat)) {
if (cat_c == '\n')
catcount++;
if (catcount > 8) {
fscanf(cat, "%f", &c[catcount-9].num);
fscanf(cat, "%f", &c[catcount-9].x);
fscanf(cat, "%f", &c[catcount-9].y);
fscanf(cat, "%f", &c[catcount-9].xworld);
fscanf(cat, "%f", &c[catcount-9].yworld);
fscanf(cat, "%f", &c[catcount-9].flux_auto);
fscanf(cat, "%f", &c[catcount-9].mag_auto);
fscanf(cat, "%f", &c[catcount-9].awin);
fscanf(cat, "%f", &c[catcount-9].bwin);
}
}
}
printf("\n");
printf("The .cat file has %d lines. \n", catcount);
printf("\n");
printf("\n");
printf("CAT CONTENTS\n");
for (i = 0; (i < catcount-9); i++) {
printf("%lf\t %lf\t %lf\t %lf\t %lf\t %lf\t %lf\t %lf\t %lf\n",
c[i].num, c[i].x, c[i].y, c[i].xworld, c[i].yworld,
c[i].flux_auto, c[i].mag_auto, c[i].awin, c[i].bwin);
}
printf("\n");
printf("\n");
// searching in the files for a match
for (i = 0; (i <= (fcatcount-5)); i++){
for (j = 0; (j <= (catcount-9)); j++) {
if (fabs(f[i].x - c[j].x) < FLT_EPSILON && fabs(f[i].y - c[j].y) < FLT_EPSILON) {
printf("%f\t .fcat line: %d\t .cat line: %d\n", c[j].x, i, j);
match++;
}
}
}
printf("\n");
printf("\n");
printf("The files have %d matches. \n", match);
fclose(fcat);
fclose(cat);
free(f);
free(c);
return 0;
}

Answer 1

You only allocated space for one fcat_s:
fcat_s *f = (fcat_s*)malloc(sizeof(fcat_s));
But in your first loop, you are already treating f like an array:
...
fscanf(fcat, "%f", &f[fcatcount-5].x);
...
Unless I am missing something, it seems that you are reading and writing to unallocated memory. I am surprised your program doesn't segfault.