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

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)

GNU                                                                            2021-08-27                                                                      STRSTR(3)