text: STRSTR(3) BSD Programmer's Manual STRSTR(3)
  strstr, strcasestr - locate a substring in a string
  #include <string.h> char * strstr(const char *big, const char *little); char * strcasestr(const char *big, const char *little);
  The strstr() function locates the first occurrence of the NUL-terminated string little in the NUL-terminated string big. The strcasestr() function is similar to strstr() but ignores the case of both strings. If little is an empty string, big is returned; if little occurs nowhere in big, NULL is returned; otherwise a pointer to the first character of the first occurrence of little is returned.
  memchr(3), strchr(3), strcspn(3), strpbrk(3), strrchr(3), strsep(3), strspn(3), strtok(3)
  The strstr().