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strstr(3) Library Functions Manual strstr(3)

NAME

strstr - string search substring

LIBRARY

Standard C library (libc-lc)

SYNOPSIS

#include <string.h>
char *strstr(const char *haystack, const char *needle);

DESCRIPTION

strstr() finds the first occurrence of the substring needle in the string haystack.

The terminating null bytes ('\0') are not compared.

It is equivalent to


memmem(haystack, strlen(haystack), needle, strlen(needle))

RETURN VALUE

strstr(3) returns 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

STANDARDS

C11, POSIX.1-2008.

HISTORY

POSIX.1-2001, C89.

SEE ALSO

strcasestr(3), strchr(3), string(3), strpbrk(3), strsep(3), strspn(3), wcsstr(3)

2026-08-10 Linux man-pages 6.19