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Add description of rawmemchr().

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Michael Kerrisk 2008-07-08 12:08:16 +00:00
parent 5e5c87978d
commit 2a8bb904db
1 changed files with 60 additions and 5 deletions
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man3/memchr.3
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@ -1,4 +1,6 @@
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\" and Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
.\" <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
@ -23,18 +25,29 @@
.\" Modified Mon Apr 12 12:49:57 1993, David Metcalfe
.\" Modified Sat Jul 24 18:56:22 1993, Rik Faith (faith@cs.unc.edu)
.\" Modified Wed Feb 20 21:09:36 2002, Ian Redfern (redferni@logica.com)
.\" 2008-07-09, mtk, add rawmemchr()
.\"
.TH MEMCHR 3 2003-11-01 "" "Linux Programmer's Manual"
.TH MEMCHR 3 2008-07-09 "" "Linux Programmer's Manual"
.SH NAME
memchr, memrchr \- scan memory for a character
memchr, memrchr, rawmemchr \- scan memory for a character
.SH SYNOPSIS
.nf
.B #include <string.h>
.sp
.BI "void *memchr(const void *" s ", int " c ", size_t " n );
.sp
.BI "void *memrchr(const void *" s ", int " c ", size_t " n );
.BI "void *rawmemchr(const void *" s ", int " c );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR rawmemchr ():
_GNU_SOURCE
.SH DESCRIPTION
The
.BR memchr ()
@ -49,7 +62,39 @@ function is like the
.BR memchr ()
function,
except that it searches backwards from the end of the \fIn\fP bytes
pointed to by \fIs\fP instead of forwards from the front.
pointed to by \fIs\fP instead of forwards from the beginning.
The
.BR rawmemchr ()
function is similar to
.BR memchr ():
it assumes (i.e., the programmer knows for certain)
that the character
.I c
lies somewhere in the string
.IR s ,
and so performs an optimized search
for the character
.IR c
(i.e., no checking for the terminating null byte, or use of an argument,
.IR n ,
to limit the range of the search).
If the chararacter
.I c
is not in the string
.IR s ,
then
.BR rawmemchr ()
may proceeed to search beyond the end of the string,
and the result is unspecified.
The folowing call is a fast means of locating a string's
terminating null byte:
.in +4n
.nf
char *p; rawmemchr(s,\ '\\0');
.fi
.in
.SH "RETURN VALUE"
The
.BR memchr ()
@ -58,13 +103,23 @@ and
functions return a pointer
to the matching byte or NULL if the character does not occur in
the given memory area.
The
.BR rawmemchr ()
function returns a pointer to the matching byte, if one is found.
If no matching byte is found, the result is unspecified.
.SH "CONFORMING TO"
The
.BR memchr ()
function conforms to SVr4, 4.3BSD, C89, C99, POSIX.1-2001.
The
.BR memrchr ()
function is a GNU extension, available since glibc 2.1.91.
The
.BR rawmemrchr ()
function is a GNU extension, available since glibc 2.1.
.SH "SEE ALSO"
.BR index (3),
.BR rindex (3),