MEMCHR
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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NAME
memchr, memrchr, rawmemchr - scan memory for a character
SYNOPSIS
#include <string.h>
void *memchr(const void *s, int c, size_t n);
void *memrchr(const void *s, int c, size_t n);
void *rawmemchr(const void *s, int c);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
memrchr(),
rawmemchr():
_GNU_SOURCE
DESCRIPTION
The
memchr()
function scans the initial
n
bytes of the memory
area pointed to by
s
for the first instance of
c.
Both
c
and the bytes of the memory area pointed to by
s
are interpreted as
unsigned char.
The
memrchr()
function is like the
memchr()
function,
except that it searches backward from the end of the
n
bytes pointed to by
s
instead of forward from the beginning.
The
rawmemchr()
function is similar to
memchr():
it assumes (i.e., the programmer knows for certain)
that an instance of
c
lies somewhere in the memory area starting at the location pointed to by
s,
and so performs an optimized search for
c
(i.e., no use of a count argument to limit the range of the search).
If an instance of
c
is not found, the results are unpredictable.
The following call is a fast means of locating a string's
terminating null byte:
char *p = rawmemchr(s, aq\0aq);
RETURN VALUE
The
memchr()
and
memrchr()
functions return a pointer
to the matching byte or NULL if the character does not occur in
the given memory area.
The
rawmemchr()
function returns a pointer to the matching byte, if one is found.
If no matching byte is found, the result is unspecified.
VERSIONS
rawmemchr()
first appeared in glibc in version 2.1.
memrchr()
first appeared in glibc in version 2.2.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
memchr(),
memrchr(),
rawmemchr()
| Thread safety | MT-Safe
|
CONFORMING TO
memchr():
POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
The
memrchr()
function is a GNU extension, available since glibc 2.1.91.
The
rawmemchr()
function is a GNU extension, available since glibc 2.1.
SEE ALSO
bstring(3),
ffs(3),
index(3),
memmem(3),
rindex(3),
strchr(3),
strpbrk(3),
strrchr(3),
strsep(3),
strspn(3),
strstr(3),
wmemchr(3)
COLOPHON
This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- VERSIONS
-
- ATTRIBUTES
-
- CONFORMING TO
-
- SEE ALSO
-
- COLOPHON
-
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