perlfaq3.pod

来自「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.」· POD 代码 · 共 1,055 行 · 第 1/3 页

=over 4

=item Elvis

ftp://ftp.cs.pdx.edu/pub/elvis/ http://www.fh-wedel.de/elvis/

=item Vile

http://dickey.his.com/vile/vile.html

=item Vim

http://www.vim.org/

=back

For vi lovers in general, Windows or elsewhere:

	http://www.thomer.com/thomer/vi/vi.html

nvi ( http://www.bostic.com/vi/ , available from CPAN in src/misc/) is
yet another vi clone, unfortunately not available for Windows, but in
UNIX platforms you might be interested in trying it out, firstly because
strictly speaking it is not a vi clone, it is the real vi, or the new
incarnation of it, and secondly because you can embed Perl inside it
to use Perl as the scripting language.  nvi is not alone in this,
though: at least also vim and vile offer an embedded Perl.

The following are Win32 multilanguage editor/IDESs that support Perl:

=over 4

=item Codewright

http://www.borland.com/codewright/

=item MultiEdit

http://www.MultiEdit.com/

=item SlickEdit

http://www.slickedit.com/

=back

There is also a toyedit Text widget based editor written in Perl
that is distributed with the Tk module on CPAN.  The ptkdb
( http://ptkdb.sourceforge.net/ ) is a Perl/tk based debugger that
acts as a development environment of sorts.  Perl Composer
( http://perlcomposer.sourceforge.net/ ) is an IDE for Perl/Tk
GUI creation.

In addition to an editor/IDE you might be interested in a more
powerful shell environment for Win32.  Your options include

=over 4

=item Bash

from the Cygwin package ( http://sources.redhat.com/cygwin/ )

=item Ksh

from the MKS Toolkit ( http://www.mks.com/ ), or the Bourne shell of
the U/WIN environment ( http://www.research.att.com/sw/tools/uwin/ )

=item Tcsh

ftp://ftp.astron.com/pub/tcsh/ , see also
http://www.primate.wisc.edu/software/csh-tcsh-book/

=item Zsh

http://www.zsh.org/

=back

MKS and U/WIN are commercial (U/WIN is free for educational and
research purposes), Cygwin is covered by the GNU Public License (but
that shouldn't matter for Perl use).  The Cygwin, MKS, and U/WIN all
contain (in addition to the shells) a comprehensive set of standard
UNIX toolkit utilities.

If you're transferring text files between Unix and Windows using FTP
be sure to transfer them in ASCII mode so the ends of lines are
appropriately converted.

On Mac OS the MacPerl Application comes with a simple 32k text editor
that behaves like a rudimentary IDE.  In contrast to the MacPerl Application
the MPW Perl tool can make use of the MPW Shell itself as an editor (with
no 32k limit).

=over 4

=item Affrus

is a full Perl development environment with full debugger support
( http://www.latenightsw.com ).

=item Alpha

is an editor, written and extensible in Tcl, that nonetheless has
built in support for several popular markup and programming languages
including Perl and HTML ( http://www.his.com/~jguyer/Alpha/Alpha8.html ).

=item BBEdit and BBEdit Lite

are text editors for Mac OS that have a Perl sensitivity mode
( http://web.barebones.com/ ).


=back

Pepper and Pe are programming language sensitive text editors for Mac
OS X and BeOS respectively ( http://www.hekkelman.com/ ).

=head2 Where can I get Perl macros for vi?

For a complete version of Tom Christiansen's vi configuration file,
see http://www.cpan.org/authors/Tom_Christiansen/scripts/toms.exrc.gz ,
the standard benchmark file for vi emulators.  The file runs best with nvi,
the current version of vi out of Berkeley, which incidentally can be built
with an embedded Perl interpreter--see http://www.cpan.org/src/misc/ .

=head2 Where can I get perl-mode for emacs?

Since Emacs version 19 patchlevel 22 or so, there have been both a
perl-mode.el and support for the Perl debugger built in.  These should
come with the standard Emacs 19 distribution.

In the Perl source directory, you'll find a directory called "emacs",
which contains a cperl-mode that color-codes keywords, provides
context-sensitive help, and other nifty things.

Note that the perl-mode of emacs will have fits with C<"main'foo">
(single quote), and mess up the indentation and highlighting.  You
are probably using C<"main::foo"> in new Perl code anyway, so this
shouldn't be an issue.

=head2 How can I use curses with Perl?

The Curses module from CPAN provides a dynamically loadable object
module interface to a curses library.  A small demo can be found at the
directory http://www.cpan.org/authors/Tom_Christiansen/scripts/rep.gz ;
this program repeats a command and updates the screen as needed, rendering
B<rep ps axu> similar to B<top>.

=head2 How can I write a GUI (X, Tk, Gtk, etc.) in Perl?
X<GUI> X<Tk> X<Wx> X<WxWidgets> X<Gtk> X<Gtk2> X<CamelBones> X<Qt>

(contributed by Ben Morrow)

There are a number of modules which let you write GUIs in Perl. Most
GUI toolkits have a perl interface: an incomplete list follows.

=over 4

=item Tk

This works under Unix and Windows, and the current version doesn't
look half as bad under Windows as it used to. Some of the gui elements
still don't 'feel' quite right, though. The interface is very natural
and 'perlish', making it easy to use in small scripts that just need a
simple gui. It hasn't been updated in a while.

=item Wx

This is a Perl binding for the cross-platform wxWidgets toolkit 
L<http://www.wxwidgets.org>. It works under Unix, Win32 and Mac OS X,
using native widgets (Gtk under Unix). The interface follows the C++
interface closely, but the documentation is a little sparse for someone
who doesn't know the library, mostly just referring you to the C++
documentation.

=item Gtk and Gtk2

These are Perl bindings for the Gtk toolkit L<http://www.gtk.org>. The
interface changed significantly between versions 1 and 2 so they have
separate Perl modules. It runs under Unix, Win32 and Mac OS X (currently
it requires an X server on Mac OS, but a 'native' port is underway), and
the widgets look the same on every plaform: i.e., they don't match the
native widgets. As with Wx, the Perl bindings follow the C API closely,
and the documentation requires you to read the C documentation to
understand it.

=item Win32::GUI

This provides access to most of the Win32 GUI widgets from Perl.
Obviously, it only runs under Win32, and uses native widgets. The Perl
interface doesn't really follow the C interface: it's been made more
Perlish, and the documentation is pretty good. More advanced stuff may
require familiarity with the C Win32 APIs, or reference to MSDN.

=item CamelBones

CamelBones L<http://camelbones.sourceforge.net> is a Perl interface to
Mac OS X's Cocoa GUI toolkit, and as such can be used to produce native
GUIs on Mac OS X. It's not on CPAN, as it requires frameworks that
CPAN.pm doesn't know how to install, but installation is via the
standard OSX package installer. The Perl API is, again, very close to
the ObjC API it's wrapping, and the documentation just tells you how to
translate from one to the other.

=item Qt

There is a Perl interface to TrollTech's Qt toolkit, but it does not
appear to be maintained.

=item Athena

Sx is an interface to the Athena widget set which comes with X, but
again it appears not to be much used nowadays.

=back

=head2 How can I make my Perl program run faster?

The best way to do this is to come up with a better algorithm.  This
can often make a dramatic difference.  Jon Bentley's book
I<Programming Pearls> (that's not a misspelling!)  has some good tips
on optimization, too.  Advice on benchmarking boils down to: benchmark
and profile to make sure you're optimizing the right part, look for
better algorithms instead of microtuning your code, and when all else
fails consider just buying faster hardware.  You will probably want to
read the answer to the earlier question "How do I profile my Perl
programs?" if you haven't done so already.

A different approach is to autoload seldom-used Perl code.  See the
AutoSplit and AutoLoader modules in the standard distribution for
that.  Or you could locate the bottleneck and think about writing just
that part in C, the way we used to take bottlenecks in C code and
write them in assembler.  Similar to rewriting in C, modules that have
critical sections can be written in C (for instance, the PDL module
from CPAN).

If you're currently linking your perl executable to a shared
I<libc.so>, you can often gain a 10-25% performance benefit by
rebuilding it to link with a static libc.a instead.  This will make a
bigger perl executable, but your Perl programs (and programmers) may
thank you for it.  See the F<INSTALL> file in the source distribution
for more information.

The undump program was an ancient attempt to speed up Perl program by
storing the already-compiled form to disk.  This is no longer a viable
option, as it only worked on a few architectures, and wasn't a good
solution anyway.

=head2 How can I make my Perl program take less memory?

When it comes to time-space tradeoffs, Perl nearly always prefers to
throw memory at a problem.  Scalars in Perl use more memory than
strings in C, arrays take more than that, and hashes use even more.  While
there's still a lot to be done, recent releases have been addressing
these issues.  For example, as of 5.004, duplicate hash keys are
shared amongst all hashes using them, so require no reallocation.

In some cases, using substr() or vec() to simulate arrays can be
highly beneficial.  For example, an array of a thousand booleans will
take at least 20,000 bytes of space, but it can be turned into one
125-byte bit vector--a considerable memory savings.  The standard
Tie::SubstrHash module can also help for certain types of data
structure.  If you're working with specialist data structures
(matrices, for instance) modules that implement these in C may use
less memory than equivalent Perl modules.

Another thing to try is learning whether your Perl was compiled with
the system malloc or with Perl's builtin malloc.  Whichever one it
is, try using the other one and see whether this makes a difference.
Information about malloc is in the F<INSTALL> file in the source
distribution.  You can find out whether you are using perl's malloc by
typing C<perl -V:usemymalloc>.

Of course, the best way to save memory is to not do anything to waste
it in the first place. Good programming practices can go a long way
toward this:

=over 4

=item * Don't slurp!

Don't read an entire file into memory if you can process it line
by line. Or more concretely, use a loop like this:

	#
	# Good Idea
	#
	while (<FILE>) {
	   # ...
	}

instead of this:

	#
	# Bad Idea
	#
	@data = <FILE>;
	foreach (@data) {
	    # ...
	}

When the files you're processing are small, it doesn't much matter which
way you do it, but it makes a huge difference when they start getting
larger.

=item * Use map and grep selectively

Remember that both map and grep expect a LIST argument, so doing this:

        @wanted = grep {/pattern/} <FILE>;

will cause the entire file to be slurped. For large files, it's better
to loop:

        while (<FILE>) {
                push(@wanted, $_) if /pattern/;
        }

=item * Avoid unnecessary quotes and stringification

Don't quote large strings unless absolutely necessary:

        my $copy = "$large_string";

makes 2 copies of $large_string (one for $copy and another for the
quotes), whereas

        my $copy = $large_string;

only makes one copy.

Ditto for stringifying large arrays:

        {
                local $, = "\n";
                print @big_array;
        }

is much more memory-efficient than either

        print join "\n", @big_array;

or

        {
                local $" = "\n";
                print "@big_array";
        }


=item * Pass by reference