Write untill i find an empty line in C

I'm trying to find all data for a day (Monday, Tuesday...) and write the data below. My txt document is written as:

Monday .......
..............
..............

Tuesday.......
..............
..............

Monday........
..............
..............

The only thing that is separating days is an empty line. I successfully find the day in a file, the problem is that I need to print all the data until an empty line occurs. For instance, if I select Monday(selectedday="Monday"), my output should be:

Monday .......
..............
..............

Monday .......
..............
..............

The code I've tried:

    int main()
    {
        char string[100], selectedday[] = "monday"; //for Monday
        FILE* openbill;
        openbill= fopen("bill.txt", "r");
        if (openbill== NULL)
        {
            printf("Failed to open bill\n");
            return NULL;
        }
        while (fscanf(openbill, "%s", string) == 1)
        {
            if (strstr(openbill, selectedday) != 0)
            {
                printf("%s", string);
               
            }
        }
    }

Thank you for your help.

The scanset %2[\n] tells fscanf to scan up to two characters and only scan newlines.
The format string "%99s" tells fscanf to scan up to 99 non-whitespace characters into string. This allows room for the terminating zero.
output is a flag that is set to 1 when the day is found and set to 0 when a pair of newlines is scanned. A 1 enables output and string will be printed.

#include <stdio.h>
#include <string.h>

void showday ( char *selectedday) {
    char string[100] = "";
    char newline[3] = "";
    int result = 0;
    int output = 0;
    FILE* openbill = NULL;

    openbill = fopen ( "bill.txt", "r");
    if ( openbill == NULL) {
        perror ( "bill.txt");
        return;
    }
    do {
        string[0] = 0;//set empty string
        if ( 1 == ( result = fscanf ( openbill, "%2[\n]", newline))) {
            if ( output) {//enabled
                printf ( "%s", newline);
            }
            if ( '\n' == newline[1]) {//two newlines
                output = 0;//disable
            }
        }
        else {
            result = fscanf ( openbill, "%99s", string);
            if ( strstr ( string, selectedday)) {
                output = 1;//enable
            }
        }
        if ( output && string[0]) {//enabled and string not empty
            printf ( "%s ", string);
        }
    } while ( EOF != result);

    fclose ( openbill);

}

int main ( void) {

    showday ( "monday");

    return 0;
}