perl571delta.1

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.\" ========================================================================
.\"
.IX Title "PERL571DELTA 1"
.TH PERL571DELTA 1 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
perl571delta \- what's new for perl v5.7.1
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This document describes differences between the 5.7.0 release and the
5.7.1 release.
.PP
(To view the differences between the 5.6.0 release and the 5.7.0
release, see perl570delta.)
.SH "Security Vulnerability Closed"
.IX Header "Security Vulnerability Closed"
(This change was already made in 5.7.0 but bears repeating here.)
.PP
A potential security vulnerability in the optional suidperl component
of Perl was identified in August 2000.  suidperl is neither built nor
installed by default.  As of April 2001 the only known vulnerable
platform is Linux, most likely all Linux distributions.  \s-1CERT\s0 and
various vendors and distributors have been alerted about the vulnerability.
See http://www.cpan.org/src/5.0/sperl\-2000\-08\-05/sperl\-2000\-08\-05.txt
for more information.
.PP
The problem was caused by Perl trying to report a suspected security
exploit attempt using an external program, /bin/mail.  On Linux
platforms the /bin/mail program had an undocumented feature which
when combined with suidperl gave access to a root shell, resulting in
a serious compromise instead of reporting the exploit attempt.  If you
don't have /bin/mail, or if you have 'safe setuid scripts', or if
suidperl is not installed, you are safe.
.PP
The exploit attempt reporting feature has been completely removed from
all the Perl 5.7 releases (and will be gone also from the maintenance
release 5.6.1), so that particular vulnerability isn't there anymore.
However, further security vulnerabilities are, unfortunately, always
possible.  The suidperl code is being reviewed and if deemed too risky
to continue to be supported, it may be completely removed from future
releases.  In any case, suidperl should only be used by security
experts who know exactly what they are doing and why they are using
suidperl instead of some other solution such as sudo
( see http://www.courtesan.com/sudo/ ).
.SH "Incompatible Changes"
.IX Header "Incompatible Changes"
.IP "\(bu" 4
Although \*(L"you shouldn't do that\*(R", it was possible to write code that
depends on Perl's hashed key order (Data::Dumper does this).  The new
algorithm \*(L"One-at-a-Time\*(R" produces a different hashed key order.
More details are in \*(L"Performance Enhancements\*(R".
.IP "\(bu" 4
The list of filenames from \fIglob()\fR (or <...>) is now by default sorted
alphabetically to be csh-compliant.  (\fIbsd_glob()\fR does still sort platform
natively, \s-1ASCII\s0 or \s-1EBCDIC\s0, unless \s-1GLOB_ALPHASORT\s0 is specified.)
.SH "Core Enhancements"
.IX Header "Core Enhancements"
.Sh "\s-1AUTOLOAD\s0 Is Now Lvaluable"
.IX Subsection "AUTOLOAD Is Now Lvaluable"
\&\s-1AUTOLOAD\s0 is now lvaluable, meaning that you can add the :lvalue attribute
to \s-1AUTOLOAD\s0 subroutines and you can assign to the \s-1AUTOLOAD\s0 return value.
.Sh "PerlIO is Now The Default"
.IX Subsection "PerlIO is Now The Default"
.IP "\(bu" 4
\&\s-1IO\s0 is now by default done via PerlIO rather than system's \*(L"stdio\*(R".
PerlIO allows \*(L"layers\*(R" to be \*(L"pushed\*(R" onto a file handle to alter the
handle's behaviour.  Layers can be specified at open time via 3\-arg
form of open:
.Sp
.Vb 1
\&   open($fh,\*(Aq>:crlf :utf8\*(Aq, $path) || ...
.Ve
.Sp
or on already opened handles via extended \f(CW\*(C`binmode\*(C'\fR:
.Sp
.Vb 1
\&   binmode($fh,\*(Aq:encoding(iso\-8859\-7)\*(Aq);
.Ve
.Sp
The built-in layers are: unix (low level read/write), stdio (as in
previous Perls), perlio (re-implementation of stdio buffering in a
portable manner), crlf (does \s-1CRLF\s0 <=> \*(L"\en\*(R" translation as on Win32,
but available on any platform).  A mmap layer may be available if
platform supports it (mostly UNIXes).
.Sp
Layers to be applied by default may be specified via the 'open' pragma.
.Sp
See \*(L"Installation and Configuration Improvements\*(R" for the effects
of PerlIO on your architecture name.
.IP "\(bu" 4
File handles can be marked as accepting Perl's internal encoding of Unicode
(\s-1UTF\-8\s0 or UTF-EBCDIC depending on platform) by a pseudo layer \*(L":utf8\*(R" :
.Sp
.Vb 1
\&   open($fh,">:utf8","Uni.txt");
.Ve
.Sp
Note for \s-1EBCDIC\s0 users: the pseudo layer \*(L":utf8\*(R" is erroneously named
for you since it's not \s-1UTF\-8\s0 what you will be getting but instead
UTF-EBCDIC.  See perlunicode, utf8, and
http://www.unicode.org/unicode/reports/tr16/ for more information.
In future releases this naming may change.
.IP "\(bu" 4
File handles can translate character encodings from/to Perl's internal
Unicode form on read/write via the \*(L":\fIencoding()\fR\*(R" layer.
.IP "\(bu" 4
File handles can be opened to \*(L"in memory\*(R" files held in Perl scalars via:
.Sp
.Vb 1
\&   open($fh,\*(Aq>\*(Aq, \e$variable) || ...
.Ve
.IP "\(bu" 4
Anonymous temporary files are available without need to
\&'use FileHandle' or other module via
.Sp
.Vb 1
\&   open($fh,"+>", undef) || ...
.Ve
.Sp
That is a literal undef, not an undefined value.
.IP "\(bu" 4
The list form of \f(CW\*(C`open\*(C'\fR is now implemented for pipes (at least on \s-1UNIX\s0):
.Sp
.Vb 1
\&   open($fh,"\-|", \*(Aqcat\*(Aq, \*(Aq/etc/motd\*(Aq)
.Ve
.Sp
creates a pipe, and runs the equivalent of exec('cat', '/etc/motd') in
the child process.
.IP "\(bu" 4
The following builtin functions are now overridable: \fIchop()\fR, \fIchomp()\fR,
\&\fIeach()\fR, \fIkeys()\fR, \fIpop()\fR, \fIpush()\fR, \fIshift()\fR, \fIsplice()\fR, \fIunshift()\fR.
.IP "\(bu" 4
Formats now support zero-padded decimal fields.
.IP "\(bu" 4
Perl now tries internally to use integer values in numeric conversions
and basic arithmetics (+ \- * /) if the arguments are integers, and
tries also to keep the results stored internally as integers.
This change leads into often slightly faster and always less lossy
arithmetics. (Previously Perl always preferred floating point numbers
in its math.)
.IP "\(bu" 4
The \fIprintf()\fR and \fIsprintf()\fR now support parameter reordering using the
\&\f(CW\*(C`%\ed+\e$\*(C'\fR and \f(CW\*(C`*\ed+\e$\*(C'\fR syntaxes.  For example
.Sp
.Vb 1
\&    print "%2\e$s %1\e$s\en", "foo", "bar";
.Ve
.Sp
will print \*(L"bar foo\en\*(R"; This feature helps in writing
internationalised software.
.IP "\(bu" 4
Unicode in general should be now much more usable.  Unicode can be
used in hash keys, Unicode in regular expressions should work now,
Unicode in tr/// should work now (though tr/// seems to be a
particularly tricky to get right, so you have been warned)
.IP "\(bu" 4
The Unicode Character Database coming with Perl has been upgraded
to Unicode 3.1.  For more information, see http://www.unicode.org/ ,
and http://www.unicode.org/unicode/reports/tr27/
.Sp
For developers interested in enhancing Perl's Unicode capabilities:
almost all the \s-1UCD\s0 files are included with the Perl distribution in
the lib/unicode subdirectory.  The most notable omission, for space
considerations, is the Unihan database.
.IP "\(bu" 4
The Unicode character classes \ep{Blank} and \ep{SpacePerl} have been
added.  \*(L"Blank\*(R" is like C \fIisblank()\fR, that is, it contains only
\&\*(L"horizontal whitespace\*(R" (the space character is, the newline isn't),
and the \*(L"SpacePerl\*(R" is the Unicode equivalent of \f(CW\*(C`\es\*(C'\fR (\ep{Space}
isn't, since that includes the vertical tabulator character, whereas
\&\f(CW\*(C`\es\*(C'\fR doesn't.)
.Sh "Signals Are Now Safe"
.IX Subsection "Signals Are Now Safe"
Perl used to be fragile in that signals arriving at inopportune moments
could corrupt Perl's internal state.
.SH "Modules and Pragmata"
.IX Header "Modules and Pragmata"
.Sh "New Modules"
.IX Subsection "New Modules"
.IP "\(bu" 4
B::Concise, by Stephen McCamant, is a new compiler backend for
walking the Perl syntax tree, printing concise info about ops.
The output is highly customisable.
.Sp
See B::Concise for more information.
.IP "\(bu" 4
Class::ISA, by Sean Burke, for reporting the search path for a
class's \s-1ISA\s0 tree, has been added.
.Sp
See Class::ISA for more information.
.IP "\(bu" 4
Cwd has now a split personality: if possible, an extension is used,
(this will hopefully be both faster and more secure and robust) but
if not possible, the familiar Perl library implementation is used.