NAME

strstr, strcasestr, strnstr — locate a substring in a string

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <string.h>

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

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

char *
strnstr(const char *haystack, const char *needle, size_t len);

#include <string.h>
#include <xlocale.h>

char *
strcasestr_l(const char *haystack, const char *needle, locale_t loc);

DESCRIPTION

The strstr() function locates the first occurrence of the null-terminated string needle in the null-terminated string haystack.

The strcasestr() function is similar to strstr(), but ignores the case of both strings.

The strnstr() function locates the first occurrence of the null-terminated string needle in the string haystack, where not more than len characters are searched. Characters that appear after a ‘\0’ character are not searched. Since the strnstr() function is a FreeBSD specific API, it should only be used when portability is not a concern.

While the strcasestr() function uses the current locale, the strcasestr_l() function may be passed a locale directly. See xlocale(3) for more information.

RETURN VALUES

If needle is an empty string, haystack is returned; if needle occurs nowhere in haystack, NULL is returned; otherwise a pointer to the first character of the first occurrence of needle is returned.

EXAMPLES

The following sets the pointer ptr to the "Bar Baz" portion of largestring:

const char *largestring = "Foo Bar Baz";
const char *smallstring = "Bar";
char *ptr;

ptr = strstr(largestring, smallstring);

The following sets the pointer ptr to NULL, because only the first 4 characters of largestring are searched:

const char *largestring = "Foo Bar Baz";
const char *smallstring = "Bar";
char *ptr;

ptr = strnstr(largestring, smallstring, 4);

SEE ALSO

memchr(3), memmem(3), strchr(3), strcspn(3), strpbrk(3), strrchr(3), strsep(3), strspn(3), strtok(3), wcsstr(3), xlocale(3)

STANDARDS

The strstr() function conforms to ISO/IEC 9899:1990 (“ISO C90”).