C语言字符串查找替换

void str_run(char *primary_str, char *lookup_str, char* replace_str, char* new_str)

{        //功能是在primary_str中查找lookup_str, 找到lookup_str则替换成replace_str, 否则不替换, 返回新的new_str

int cn = 0, cL = 0;

char  *pPstr = primary_str, *pLstr = lookup_str, *pRstr = replace_str, *pNew_str