Question

Why does this particular piece of code return false on the strstr() if I input “test”?

char input[100];

int main()
{
    fgets(input, 100, stdin);
    printf("%s", input);

    if(strstr("test message", input))
    {
        printf("strstr true");

    }


}

I thought strstr searched the first param for instances of the second param? It works when I replace input with some text or just assign it something directly, but it seems to not work with fgets.

Answer 1

It’s because fgets stores the newline character so when strstr does a comparison it fails.

From the man page:

fgets() reads in at most one less than size characters from stream
and stores them into the buffer pointed to by s. Reading stops after
an EOF or a newline. If a newline is read, it is stored
into the buffer. A ‘\0’ is stored after the last character in the buffer.