redhat man page for strstr

STRSTR(3)						     Linux Programmer's Manual							 STRSTR(3)

NAME
       strstr - locate a substring

SYNOPSIS
       #include <string.h>

       char *strstr(const char *haystack, const char *needle);

DESCRIPTION
       The  strstr()  function finds the first occurrence of the substring needle in the string haystack.  The terminating `' characters are not
       compared.

RETURN VALUE
       The strstr() function returns a pointer to the beginning of the substring, or NULL if the substring is not found.

BUGS
       Early versions of Linux libc (like 4.5.26) would not allow an empty argument. Later versions  (like  4.6.27)  work  correctly,  and  return
       haystack when needle is empty.

CONFORMING TO
       ISO 9899

SEE ALSO
       index(3), memchr(3), rindex(3), strchr(3), strpbrk(3), strsep(3), strspn(3), strtok(3)

GNU
								    1993-04-12								 STRSTR(3)