Question

There is a code snippet,

int matchhere(char *regexp, char  *text)
 {
    /* do sth */
    return    *test== '\0';
 }

I do not understand what does

return    *test== '\0';

mean. Or what it will return? How does “==” function here?

Answer 1

The *test part reads the first character for the C string (a C string is merely a bunch of characters starting at a given address, and the *foo operator looks at that address which happens to contain the first character). By definition, a C string ends with a null byte ('\0' or simply 0).

So this tests whether the first character is the end-of-string character. Or in other words: it tests whether the string is empty. That comparison result (1 if empty, 0 if non-empty) is returned.