strstr(3)                  Library Functions Manual                  strstr(3)

NAME
       strstr, strcasestr - locate a substring

LIBRARY
       Standard C library (libc, -lc)

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 |
       +-------------------------------------+---------------+----------------+
STANDARDS
       strstr()
              C11, POSIX.1-2008.

       strcasestr()
              GNU.

HISTORY
       strstr()
              POSIX.1-2001, C89.

       strcasestr()
              GNU.

SEE ALSO
       memchr(3), memmem(3), strcasecmp(3), strchr(3), string(3), strpbrk(3),
       strsep(3), strspn(3), strtok(3), wcsstr(3)

Linux man-pages 6.7               2023-10-31                         strstr(3)