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.

ATTRIBUTES

  Multithreading (see pthreads(7))
The strstr() function is thread-safe.

The strcasestr() function is thread-safe with exceptions. It can be safely used in multithreaded applications, as long as setlocale(3) is not called to change the locale during its execution.

CONFORMING TO
The strstr() function conforms to C89 and C99. The strcasestr() function is a nonstandard extension.

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

SEE ALSO
index(3), memchr(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 3.65 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.