strstr works only if my substring is at the end of string

Question

I\'ve encountered a couple of problems with the program that i\'m writing now.

1. strstr outputs my substring only if it\'s at the end of my string

Answer 1

You read one string with fgets() and the other with getchar() upto the end of file. There is a trailing '\n' at the end of both strings, Hence strstr() can only match the substring if it is at the end of the main string. Furthermore, you do not store a final '\0' at the end of haystack. You must do this because haystack is a local array (automatic storage), and as such is not initialized implicitly.

You can correct the problem this way:

//getting my substring here (needle)
if (!fgets(needle, sizeof(needle), stdin)) {
    // unexpected EOF, exit
    exit(1);
}
needle[strcspn(needle, "\n")] = '\0';

//getting my string here (haystack)
if (!fgets(haystack, sizeof(haystack), stdin)) {
    // unexpected EOF, exit
    exit(1);
}
haystack[strcspn(haystack, "\n")] = '\0';