string cmparison

I have to search a specific string in a file.Here i am using 'strcmp' function but its not working properly.when am compiling it in linux using gcc it does not shows any error.i couldn't catch the mistake.

#include<stdio.h>
#include<string.h>
void main()
{
	FILE * fpi;
	int totallines=0,headerlines;
	char s1[100],s2[100],str1[]="END OF HEADER";
	fpi=fopen("rinexinput.txt","r");
	if(fpi==NULL)
	{
		printf("error in opening file");
	}
	while(!feof(fpi))
	{
		fgets(s1,100,fpi);
		totallines++;
		if(strcmp(str1,s1) == 0)
		{
			headerlines=totallines;
			exit(0);
		}
	}
	printf("%s %d\n",s1,headerlines);
}