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); |
![[Note]](../stylesheet/note.png) |
Note | ||
|---|---|---|---|
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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, '\0');
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)