strstr

/* finds the next instance of needle in haystack 
   zbpos: the zero-based position to begin searching from
   haystack: the string to search in
   needle: the string that must be found
   returns the next match of `needle` in `haystack`, or -1 if not found
*/
int findnext(int zbpos, const char *haystack, const char *needle)
{
    char *p; 

    if (((p = strstr(haystack + zbpos, needle)) != NULL)
        return p - haystack;

    return -1;
}

strstr 在 needle（第一個）引數中搜尋 needle 指向的字串。如果找到，strstr 將返回事件的地址。如果找不到 needle，則返回 NULL。我們使用 zbpos，以便我們不會一遍又一遍地找到相同的針。為了跳過第一個例項，我們新增了 zbpos 的偏移量。記事本克隆可能會像這樣呼叫 findnext，以實現其查詢下一個對話方塊：

/*
    Called when the user clicks "Find Next"
    doc: The text of the document to search
    findwhat: The string to find
*/
void onfindnext(const char *doc, const char *findwhat)
{
    static int i;

    if ((i = findnext(i, doc, findwhat)) != -1)
        /* select the text starting from i and ending at i + strlen(findwhat) */
    else
        /* display a message box saying "end of search" */
}