NAME

       strstr, strcasestr - locate a substring

SYNOPSIS

       #include <string.h>

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

       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #include <string.h>

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

DESCRIPTION

       The  strstr()  function  finds  the first occurrence of the substring needle in the string
       haystack.  The terminating null bytes ('\0') are not compared.

       The strcasestr() function is like strstr(), but ignores the case of both arguments.

RETURN VALUE

       These functions return a pointer to the beginning of the located substring, or NULL if the
       substring is not found.

       If needle is the empty string, the return value is always haystack itself.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌────────────────────────────────────────────────────────┬───────────────┬────────────────┐
       │Interface                                               │ Attribute     │ Value          │
       ├────────────────────────────────────────────────────────┼───────────────┼────────────────┤
       │strstr()                                                │ Thread safety │ MT-Safe        │
       ├────────────────────────────────────────────────────────┼───────────────┼────────────────┤
       │strcasestr()                                            │ Thread safety │ MT-Safe locale │
       └────────────────────────────────────────────────────────┴───────────────┴────────────────┘

CONFORMING TO

       strstr(): POSIX.1-2001, POSIX.1-2008, C89, C99.

       The strcasestr() function is a nonstandard extension.

SEE ALSO

       index(3),   memchr(3),   memmem(3),   rindex(3),   strcasecmp(3),   strchr(3),  string(3),
       strpbrk(3), strsep(3), strspn(3), strtok(3), wcsstr(3)

COLOPHON

       This page is part of release 5.13 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at https://www.kernel.org/doc/man-pages/.