Thread: Recognize if the floating number is valid or not in C

I can now validate whether a number is a valid float number or not but i'm having problems in getting the values from a text file. Can someone help me?

Code:

#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>

int check_floatnum(double *output)
{
	double floatnum;
	FILE *fp1;
	char *end, fnum[32];

	if(fgets(fnum, sizeof(fnum), stdin) && !isspace(*fnum) && (*output = strtod(fnum, &end)), ( *end == '\n' || *end == '\0' ))
		printf("VALID\n ");
	else
		printf("INVALID\n ");
}

int main(void)
{
	double floatnum = -12.3;

	do
	{
		fp1 = fopen("C:\\input.txt","r");


	}
	while (check_floatnum(fp1));

	fclose(fp1);
}