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Add a new libc function, strnstr(3), which allows one to limit the
number of characters that are searched. This is especially useful with file operations and non-NUL terminated strings. Silence from: -audit, -hackers MFC after: 5 days
This commit is contained in:
Mike Barcroft
parent
cabacc4a0a
commit
41036d782d
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=84699
@ -30,7 +30,8 @@
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)string.h 8.1 (Berkeley) 6/2/93
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* From: @(#)string.h 8.1 (Berkeley) 6/2/93
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* $FreeBSD$
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*/
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#ifndef _STRING_H_
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@ -87,6 +88,7 @@ size_t strlcat __P((char *, const char *, size_t));
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size_t strlcpy __P((char *, const char *, size_t));
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void strmode __P((int, char *));
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int strncasecmp __P((const char *, const char *, size_t));
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char *strnstr __P((const char *, const char *, size_t));
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char *strsep __P((char **, const char *));
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char *strsignal __P((int));
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char *strtok_r __P((char *, const char *, char **));
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@ -10,6 +10,7 @@ MISRCS+=bcmp.c bcopy.c bzero.c ffs.c index.c memccpy.c memchr.c memcmp.c \
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memcpy.c memmove.c memset.c rindex.c strcasecmp.c strcat.c strchr.c \
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strcmp.c strcoll.c strcpy.c strcspn.c strdup.c strerror.c \
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strlcat.c strlcpy.c strlen.c strmode.c strncat.c strncmp.c strncpy.c \
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strnstr.c \
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strpbrk.c strrchr.c strsep.c strsignal.c strspn.c strstr.c strtok.c \
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strxfrm.c swab.c wcscat.c wcschr.c wcscmp.c wcscpy.c wcscspn.c \
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wcslcat.c wcslcpy.c wcslen.c wcsncat.c wcsncmp.c wcsncpy.c wcspbrk.c \
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@ -36,6 +37,7 @@ MLINKS+=strcpy.3 strncpy.3
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MLINKS+=strerror.3 perror.3 strerror.3 sys_errlist.3 strerror.3 sys_nerr.3
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MLINKS+=strlcpy.3 strlcat.3
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MLINKS+=strtok.3 strtok_r.3
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MLINKS+=strstr.3 strnstr.3
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MLINKS+=wmemchr.3 wmemcmp.3 wmemchr.3 wmemcpy.3 \
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wmemchr.3 wmemmove.3 wmemchr.3 wmemset.3 \
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wmemchr.3 wcscat.3 wmemchr.3 wcschr.3 \
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70
lib/libc/string/strnstr.c
Normal file
70
lib/libc/string/strnstr.c
Normal file
@ -0,0 +1,70 @@
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/*-
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* Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Chris Torek.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__RCSID("@(#)strstr.c 8.1 (Berkeley) 6/4/93");
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__FBSDID("$FreeBSD$");
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#include <string.h>
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/*
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* Find the first occurrence of find in s, where the search is limited to the
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* first slen characters of s.
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*/
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char *
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strnstr(s, find, slen)
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const char *s;
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const char *find;
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size_t slen;
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{
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char c, sc;
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size_t len;
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if ((c = *find++) != '\0') {
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len = strlen(find);
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do {
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do {
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if ((sc = *s++) == '\0' || slen-- < 1)
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return (NULL);
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} while (sc != c);
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if (len > slen)
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return (NULL);
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} while (strncmp(s, find, len) != 0);
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s--;
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}
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return ((char *)s);
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}
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@ -1,3 +1,4 @@
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.\" Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
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.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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@ -40,7 +41,7 @@
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.Dt STRSTR 3
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.Os
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.Sh NAME
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.Nm strstr
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.Nm strstr , strnstr
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.Nd locate a substring in a string
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.Sh LIBRARY
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.Lb libc
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@ -48,6 +49,8 @@
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.In string.h
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.Ft char *
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.Fn strstr "const char *big" "const char *little"
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.Ft char *
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.Fn strnstr "const char *big" "const char *little" "size_t len"
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.Sh DESCRIPTION
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The
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.Fn strstr
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@ -56,22 +59,58 @@ locates the first occurrence of the null-terminated string
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.Fa little
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in the null-terminated string
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.Fa big .
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.Pp
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The
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.Fn strnstr
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function
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locates the first occurrence of the null-terminated string
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.Fa little
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in the string
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.Fa big ,
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where only the first number of characters, identified by
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.Fa len ,
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are searched.
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.Sh RETURN VALUES
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If
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.Fa little
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is the empty string,
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.Fn strstr
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returns
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.Fa big ;
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is an empty string,
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.Fa big
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is returned;
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if
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.Fa little
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occurs nowhere in
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.Fa big ,
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.Fn strstr
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returns NULL;
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otherwise
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.Fn strstr
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returns a pointer to the first character of the first occurrence of
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.Fa little .
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NULL is returned;
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otherwise a pointer to the first character of the first occurrence of
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.Fa little
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is returned.
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.Sh EXAMPLES
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The following sets the pointer
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.Va ptr
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to the
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.Dq Li Bar Baz
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portion of
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.Va largestring :
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.Bd -literal -offset indent
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const char *largestring = "Foo Bar Baz";
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const char *smallstring = "Bar";
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char *ptr;
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ptr = strstr(largestring, smallstring);
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.Ed
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.Pp
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The following sets the pointer
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.Va ptr
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to NULL, because only the first 4 characters of
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.Va largestring
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are searched:
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.Bd -literal -offset indent
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const char *largestring = "Foo Bar Baz";
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const char *smallstring = "Bar";
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char *ptr;
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ptr = strnstr(largestring, smallstring, 4);
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.Ed
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.Sh SEE ALSO
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.Xr memchr 3 ,
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.Xr strchr 3 ,
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