strstr(3) — Linux manual page

strstr(3)                Library Functions Manual               strstr(3)

NAME         top

       strstr, strcasestr - locate a substring

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #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         top

       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         top

       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         top

       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         top

       strstr()
              C11, POSIX.1-2008.

       strcasestr()
              GNU.

HISTORY         top

       strstr()
              POSIX.1-2001, C89.

       strcasestr()
              GNU.

SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.15            2025-05-17                      strstr(3)

Pages that refer to this page: memchr(3),  memmem(3),  strchr(3),  string(3),  strpbrk(3),  strsep(3),  strspn(3),  strtok(3),  wcsstr(3),  signal-safety(7)

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