[30963] in Perl-Users-Digest
Perl-Users Digest, Issue: 2208 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Fri Feb 13 09:09:45 2009
Date: Fri, 13 Feb 2009 06:09:10 -0800 (PST)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Fri, 13 Feb 2009 Volume: 11 Number: 2208
Today's topics:
garbage collection of eval'd subs is slow(?) <myannikos@gmail.com>
Re: How to prevent XSS attacks ? <ramesh.thangamani@gmail.com>
Re: HTML::TreeBuilder issue <larry@example.invalid>
Re: Install a perl module to the main perl lib dir <larry@example.invalid>
new CPAN modules on Fri Feb 13 2009 (Randal Schwartz)
oneliner for todays UNIX date <tiroverus@yahoo.com>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@seesig.invalid
Re: Question about why a pipe doesn't block <cdalten@gmail.com>
Re: Question about why a pipe doesn't block <rweikusat@mssgmbh.com>
Simple question about binmode emcee2k@gmail.com
Re: Simple question about binmode <noreply@gunnar.cc>
Re: Simple question about binmode <tadmc@seesig.invalid>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Fri, 13 Feb 2009 04:03:06 -0800 (PST)
From: "myannikos@gmail.com" <myannikos@gmail.com>
Subject: garbage collection of eval'd subs is slow(?)
Message-Id: <26ca7f40-4f84-4fe3-bd6f-2d40cc22c362@f3g2000yqf.googlegroups.com>
I recently stumbled across this problem while using generated subs
(Perl v5.8.8):
for(;;) {
...
$sub = eval "sub { ... }";
...
}
The line containing the eval will take much longer (with about 15.000
s/// statements in the sub in my case) when the $sub is already
defined (from a previous iteration).
To put this into perspective - same "sub { ... }" definition (or
minimal differences, otherwise there would be no point in eval'ing
again):
- if $sub is undefined: about 0.5s (first iteration)
- if $sub is defined (value from previous eval): about 35-40s
If the old $sub reference is kept alive (push @junk, $sub before it is
overwritten), the second case is as fast as it should be.
Conclusion: garbage collection (or whatever else happens when the old
sub reference is no longer used) of large subs (possibly only if they
contain many s/// statements - due to lack of time I did not test
other "large" subs) is extremely slow and the workaround is rather
ugly (= keeping them alive somewhere, wasting memory). This can affect
code that uses eval'd subs rather badly, so perhaps it should be
fixed.
-mjy
------------------------------
Date: Fri, 13 Feb 2009 00:41:08 -0800 (PST)
From: rthangam <ramesh.thangamani@gmail.com>
Subject: Re: How to prevent XSS attacks ?
Message-Id: <16f1e53b-ff94-4578-9f98-3d17eb746ee6@f20g2000yqg.googlegroups.com>
On Feb 10, 12:33=A0pm, Tim Greer <t...@burlyhost.com> wrote:
> rthangam wrote:
> > I have my own website which runs on mod_perl. I need to prevent my
> > website from XSS ( Cross-site scripting ) attacks. Can anyone tell me
> > which is the best way of doing it ?. I found the following links to
> > handle it:
>
> >http://www.howtoforge.com/apache_mod_security
>
> http://search.cpan.org/~lindner/Apache-TaintRequest-0.10/TaintRequest.pm
>
>
>
> > Which of these is better also is there any other ways to handle the
> > XSS attacks?.
>
> If you don't write code that opens that potential, you needn't worry
> about using things like mod_security. =A0That's just a way to stop
> attacks on vulnerable scripts before it hits the script, which is
> backward thinking for resolving a problem (if you control the script).
> Exactly what things are you doing (and how are you going about doing
> them) where you're introducing the potential for an XSS attack issue?
> --
> Tim Greer, CEO/Founder/CTO, BurlyHost.com, Inc.
> Shared Hosting, Reseller Hosting, Dedicated & Semi-Dedicated servers
> and Custom Hosting. =A024/7 support, 30 day guarantee, secure servers.
> Industry's most experienced staff! -- Web Hosting With Muscle!
Right now it is possible to tamper the URL since I am not encoding and
decoding the URL.
Will the problem get solved if i encode and decode the URL ?
------------------------------
Date: Fri, 13 Feb 2009 01:06:31 -0700
From: Larry Gates <larry@example.invalid>
Subject: Re: HTML::TreeBuilder issue
Message-Id: <1en0rsnstql9f.8ibrfqimtjel.dlg@40tude.net>
On Thu, 5 Feb 2009 15:26:32 -0800 (PST), Dean Karres wrote:
>> Have you run this through validator?
>
> A great idea! The passed in html was very poorly formed... that was
> not part of my test case; I just threw in som nearly random html with
> H# tags mixed with A tags.
>
> After validating and cleaning the html TreeBuilder did exactly what i
> hoped it would.
>
> Which brings up a different issue. THe TreeBuilder docs say there is
> a flag "$root->warn(value)" that "determines whether syntax errors
> during parsing should generate warnings, emitted via Perl's ''warn''
> function." I set this to true and ran the script on the obviously bad
> html and saw no warnings.
>
> However, I hope I can trust my users to validate their html.
>
> cheers,
I would advise you to get the html with
use LWP::Simple;
, which has yet to fail me, now that I've used it a grand total of twice.
My current output is:
C:\MinGW\source> perl tree2.pl
i=0
i=1
i=2
i=3
i=4
i=5
i=6
i=7
i=8
21: Can't call method "look_down" without a package or object reference at
tree2
.pl line 20.
C:\MinGW\source>type tree2.pl
#!/usr/bin/perl
use warnings;
use strict;
use HTML::TreeBuilder;
my $tree = HTML::TreeBuilder->new_from_file(*DATA);
my $body = eval { $tree->look_down('_tag', 'body'); };
die __LINE__ . ": " . $@ if $@;
die "missing a BODY tag\n" unless $body;
my @bodyElementList = eval { $body->content_list(); };
die __LINE__ . ": " . $@ if $@;
foreach my $i ( 0 .. $#bodyElementList )
{
warn "i=$i\n";
my $H2 = eval { $bodyElementList[$i]->look_down('_tag', 'h2'); };
die __LINE__ . ": " . $@ if $@;
}
__DATA__
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://
www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=utf-8" />
<title>thing</title>
<link href="index.css" rel="stylesheet" type="text/css" />
</head>
<body>
<h1>A Title</h1>
<a name="foo"></a><h2>Nav topic 1</h2>
<h2><a name="foo2"></a>Nav topic 2</h2>
<h2><a name="foo3">Nav topic 3</a</h2>
<h2><a name="foo4"><a href="http://www.harvard.edu">Nav topic 4</
a></a></h2>
<h2><a href="http://www.mit.edu"><a name="foo5">Nav topic 5</a></
a></h2>
<a name="foo"><h2>Nav topic 6</h2></a>
<a href="http://www.usc.edu"> <a name="foo"> <h2>Nav topic 7</h2>
</a> </a>
</body>
</html>
# perl tree2.pl
C:\MinGW\source>
--
larry gates
Yes, we have consensus that we need 64 bit support. :-)
-- Larry Wall in <199710291922.LAA07101@wall.org>
------------------------------
Date: Fri, 13 Feb 2009 01:25:52 -0700
From: Larry Gates <larry@example.invalid>
Subject: Re: Install a perl module to the main perl lib dir
Message-Id: <ke6z0bchlrbj$.14tco3gbyafqe.dlg@40tude.net>
On Fri, 13 Feb 2009 04:52:00 +0100, Thomas Steinbach wrote:
> Hello NG,
>
> if I install new modules with the cpan
> shell (windows), the modules will be installed
> and stored under perldir/site/lib/[MODULE]
> and not under perldir/lib/[MODULE] like the "base"
> system which was installed after compiling perl
> and use dmake install.
>
> But if I look at ActiveStates Layout and
> other diestributions, they have additional
> modules installed under perldir/lib/[MODULE]
> and _NOT_ under perldir/site/lib/[MODULE]
>
> How they are made this? And Why?
>
>
> Thomas
Hello Thomas,
I've been struggling with some of your same questions but achieved a minor
breakthrough tonight.
I downloaded a recognizable, small module (Acme::something) and then
searched for it. I installed a dos window in this "fortunate place."
C:\Perl\site\lib>dir
Volume in drive C has no label.
Volume Serial Number is 942A-AD55
Directory of C:\Perl\site\lib
02/13/2009 01:15 AM <DIR> .
02/13/2009 01:15 AM <DIR> ..
02/13/2009 01:09 AM <DIR> Acme
02/13/2009 01:09 AM <DIR> auto
01/30/2009 10:06 PM <DIR> DateTime
12/29/2008 10:39 PM <DIR> HTML
02/13/2009 01:15 AM 1,425 perl4.lnk
01/23/2007 04:15 PM 31 sitecustomize.pl
2 File(s) 1,456 bytes
6 Dir(s) 66,651,992,064 bytes free
C:\Perl\site\lib>
You don't need perldir; you need the actual dir where activestate is
looking for this stuff. Peace.
--
larry gates
/* This bit of chicanery makes a unary function followed by
a parenthesis into a function with one argument, highest precedence. */
-- Larry Wall in toke.c from the perl source code
------------------------------
Date: Fri, 13 Feb 2009 05:42:26 GMT
From: merlyn@stonehenge.com (Randal Schwartz)
Subject: new CPAN modules on Fri Feb 13 2009
Message-Id: <KEzp6q.E80@zorch.sf-bay.org>
The following modules have recently been added to or updated in the
Comprehensive Perl Archive Network (CPAN). You can install them using the
instructions in the 'perlmodinstall' page included with your Perl
distribution.
Acme-CPANAuthors-Russian-0.8
http://search.cpan.org/~sharifuln/Acme-CPANAuthors-Russian-0.8/
We are Russian CPAN authors
----
AnyEvent-4.34
http://search.cpan.org/~mlehmann/AnyEvent-4.34/
provide framework for multiple event loops
----
App-Editor-GVip-0.01_01.1
http://search.cpan.org/~nkh/App-Editor-GVip-0.01_01.1/
gnome interface to Text::Editor::Vip
----
App-TimeTracker-0.20
http://search.cpan.org/~domm/App-TimeTracker-0.20/
Track time spend on projects from the commandline
----
Array-Transpose-0.02
http://search.cpan.org/~mrdvt/Array-Transpose-0.02/
Transposes a 2-Dimensional Array
----
Audio-ScratchLive-0.01
http://search.cpan.org/~capoeirab/Audio-ScratchLive-0.01/
v0.01 - this class provides simple way to read/write ScratchLive crates and databases
----
CPAN-Testers-Common-Article-0.36
http://search.cpan.org/~barbie/CPAN-Testers-Common-Article-0.36/
Parse a CPAN Testers NNTP article
----
Catalyst-View-Email-0.13
http://search.cpan.org/~jshirley/Catalyst-View-Email-0.13/
Send Email from Catalyst
----
Date-Converter-1.0
http://search.cpan.org/~andy/Date-Converter-1.0/
Convert dates between calendar systems
----
Date-Tie-0.20
http://search.cpan.org/~fglock/Date-Tie-0.20/
ISO dates made easy
----
Device-USB-0.28
http://search.cpan.org/~gwadej/Device-USB-0.28/
Use libusb to access USB devices.
----
Dist-Zilla-1.004
http://search.cpan.org/~rjbs/Dist-Zilla-1.004/
distribution builder; installer not included!
----
EBook-Tools-0.4.3
http://search.cpan.org/~azed/EBook-Tools-0.4.3/
Object class for manipulating and generating E-books
----
File-Copy-Vigilant-1.0
http://search.cpan.org/~kilna/File-Copy-Vigilant-1.0/
Copy and move files with verification and retries
----
HTML-Tested-0.50
http://search.cpan.org/~bosu/HTML-Tested-0.50/
Provides HTML widgets with the built-in means of testing.
----
HTTP-Engine-0.1.3
http://search.cpan.org/~yappo/HTTP-Engine-0.1.3/
Web Server Gateway Interface and HTTP Server Engine Drivers (Yet Another Catalyst::Engine)
----
HTTP-Engine-Middleware-0.02
http://search.cpan.org/~yappo/HTTP-Engine-Middleware-0.02/
middlewares distribution
----
IPTables-ChainMgr-0.9
http://search.cpan.org/~mrash/IPTables-ChainMgr-0.9/
Perl extension for manipulating iptables policies
----
Integer-Tiny-0.2
http://search.cpan.org/~bbkr/Integer-Tiny-0.2/
Shorten and obfuscate your Integer values. Just like IDs on YouTube!
----
Moose-0.69
http://search.cpan.org/~drolsky/Moose-0.69/
A postmodern object system for Perl 5
----
MooseX-GlobRef-Object-0.06
http://search.cpan.org/~dexter/MooseX-GlobRef-Object-0.06/
Store a Moose object in glob reference
----
Net-BitTorrent-0.049_099
http://search.cpan.org/~sanko/Net-BitTorrent-0.049_099/
BitTorrent peer-to-peer protocol class
----
Net-OpenSSH-0.29
http://search.cpan.org/~salva/Net-OpenSSH-0.29/
Perl SSH client package implemented on top of OpenSSH
----
Net-Twitter-2.07
http://search.cpan.org/~cthom/Net-Twitter-2.07/
Perl interface to twitter.com
----
POE-Component-Algorithm-Evolutionary-0.1.0
http://search.cpan.org/~jmerelo/POE-Component-Algorithm-Evolutionary-0.1.0/
Run evolutionary algorithms in a preemptive multitasking way.
----
SVN-Hooks-0.14.21
http://search.cpan.org/~gnustavo/SVN-Hooks-0.14.21/
A framework for implementing Subversion hooks.
----
Set-IntSpan-Partition-0.01
http://search.cpan.org/~bjoern/Set-IntSpan-Partition-0.01/
Partition int sets using Set::IntSpan objects
----
Simo-0.07_04
http://search.cpan.org/~kimoto/Simo-0.07_04/
Very simple framework for Object Oriented Perl.
----
Task-Padre-Plugins-0.13
http://search.cpan.org/~fayland/Task-Padre-Plugins-0.13/
Get many Plugins of Padre at once
----
Test-Behaviour-Spec-0.01
http://search.cpan.org/~tociyuki/Test-Behaviour-Spec-0.01/
Interiors of tests for the Behaviour Driven Developments.
----
Test-Data-1.22
http://search.cpan.org/~bdfoy/Test-Data-1.22/
test functions for particular variable types
----
Test-Unit-Lite-0.12
http://search.cpan.org/~dexter/Test-Unit-Lite-0.12/
Unit testing without external dependencies
----
Test-WWW-Mechanize-Catalyst-0.50_2
http://search.cpan.org/~ash/Test-WWW-Mechanize-Catalyst-0.50_2/
Test::WWW::Mechanize for Catalyst
----
Unix-Uptime-0.3201
http://search.cpan.org/~pioto/Unix-Uptime-0.3201/
Determine the current uptime, in seconds, across different *NIX architectures
----
Variable-Magic-0.30
http://search.cpan.org/~vpit/Variable-Magic-0.30/
Associate user-defined magic to variables from Perl.
----
W3C-LinkChecker-4.4
http://search.cpan.org/~scop/W3C-LinkChecker-4.4/
----
WWW-MobileCarrierJP-0.26
http://search.cpan.org/~tokuhirom/WWW-MobileCarrierJP-0.26/
scrape mobile carrier information
----
WWW-Modbot-0.01
http://search.cpan.org/~michael/WWW-Modbot-0.01/
Tools to automoderate Web-based spam
----
XML-Compile-1.01
http://search.cpan.org/~markov/XML-Compile-1.01/
Compilation based XML processing
----
XML-Compile-1.02
http://search.cpan.org/~markov/XML-Compile-1.02/
Compilation based XML processing
----
XML-Compile-Cache-0.91
http://search.cpan.org/~markov/XML-Compile-Cache-0.91/
Cache compiled XML translators
----
XML-Compile-SOAP-2.01
http://search.cpan.org/~markov/XML-Compile-SOAP-2.01/
base-class for SOAP implementations
----
XML-Compile-SOAP-Daemon-2.00
http://search.cpan.org/~markov/XML-Compile-SOAP-Daemon-2.00/
SOAP accepting server
----
XML-Compile-SOAP12-2.00
http://search.cpan.org/~markov/XML-Compile-SOAP12-2.00/
base class for SOAP1.2 implementation
----
XML-Table2XML-1.1-withoutworldwriteables
http://search.cpan.org/~rkapl/XML-Table2XML-1.1-withoutworldwriteables/
Generic conversion of tabular data to XML by reverting Excel's flattener methodology.
----
callee-0.01
http://search.cpan.org/~marcel/callee-0.01/
support recursive anonymous functions
----
mobirc-1.99_03
http://search.cpan.org/~tokuhirom/mobirc-1.99_03/
modern IRC to HTTP gateway
If you're an author of one of these modules, please submit a detailed
announcement to comp.lang.perl.announce, and we'll pass it along.
This message was generated by a Perl program described in my Linux
Magazine column, which can be found on-line (along with more than
200 other freely available past column articles) at
http://www.stonehenge.com/merlyn/LinuxMag/col82.html
print "Just another Perl hacker," # the original
--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
<merlyn@stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
Smalltalk/Perl/Unix consulting, Technical writing, Comedy, etc. etc.
See http://methodsandmessages.vox.com/ for Smalltalk and Seaside discussion
------------------------------
Date: Fri, 13 Feb 2009 14:04:19 +0000 (UTC)
From: "Tiro Verus"<tiroverus@yahoo.com>
Subject: oneliner for todays UNIX date
Message-Id: <gn3ul3$ccu$1@chessie.cirr.com>
Unix Time To Reach 1234567890 this Friday the 13th...
http://tech.slashdot.org/article.pl?sid=09/02/08/2043206&from=rss
Matias Palomec has a perl script you an use to see what
time that will be for you: perl -e 'print scalar
localtime(1234567890),"\n";' Now, while this is not the UNIX epoch,
Alan Cox does assure us that Linux is now working on 64-bit time, and
the UNIX epoch 'roll-over' would happen about the time that the sun
------------------------------
Date: Fri, 13 Feb 2009 08:15:56 GMT
From: tadmc@seesig.invalid
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
Message-Id: <0%9ll.16743$yr3.195@nlpi068.nbdc.sbc.com>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
This newsgroup, commonly called clpmisc, is a technical newsgroup
intended to be used for discussion of Perl related issues (except job
postings), whether it be comments or questions.
As you would expect, clpmisc discussions are usually very technical in
nature and there are conventions for conduct in technical newsgroups
going somewhat beyond those in non-technical newsgroups.
The article at:
http://www.catb.org/~esr/faqs/smart-questions.html
describes how to get answers from technical people in general.
This article describes things that you should, and should not, do to
increase your chances of getting an answer to your Perl question. It is
available in POD, HTML and plain text formats at:
http://www.rehabitation.com/clpmisc.shtml
For more information about netiquette in general, see the "Netiquette
Guidelines" at:
http://andrew2.andrew.cmu.edu/rfc/rfc1855.html
A note to newsgroup "regulars":
Do not use these guidelines as a "license to flame" or other
meanness. It is possible that a poster is unaware of things
discussed here. Give them the benefit of the doubt, and just
help them learn how to post, rather than assume that they do
know and are being the "bad kind" of Lazy.
A note about technical terms used here:
In this document, we use words like "must" and "should" as
they're used in technical conversation (such as you will
encounter in this newsgroup). When we say that you *must* do
something, we mean that if you don't do that something, then
it's unlikely that you will benefit much from this group.
We're not bossing you around; we're making the point without
lots of words.
Do *NOT* send email to the maintainer of these guidelines. It will be
discarded unread. The guidelines belong to the newsgroup so all
discussion should appear in the newsgroup. I am just the secretary that
writes down the consensus of the group.
Before posting to comp.lang.perl.misc
Must
This section describes things that you *must* do before posting to
clpmisc, in order to maximize your chances of getting meaningful replies
to your inquiry and to avoid getting flamed for being lazy and trying to
have others do your work.
The perl distribution includes documentation that is copied to your hard
drive when you install perl. Also installed is a program for looking
things up in that (and other) documentation named 'perldoc'.
You should either find out where the docs got installed on your system,
or use perldoc to find them for you. Type "perldoc perldoc" to learn how
to use perldoc itself. Type "perldoc perl" to start reading Perl's
standard documentation.
Check the Perl Frequently Asked Questions (FAQ)
Checking the FAQ before posting is required in Big 8 newsgroups in
general, there is nothing clpmisc-specific about this requirement.
You are expected to do this in nearly all newsgroups.
You can use the "-q" switch with perldoc to do a word search of the
questions in the Perl FAQs.
Check the other standard Perl docs (*.pod)
The perl distribution comes with much more documentation than is
available for most other newsgroups, so in clpmisc you should also
see if you can find an answer in the other (non-FAQ) standard docs
before posting.
It is *not* required, or even expected, that you actually *read* all of
Perl's standard docs, only that you spend a few minutes searching them
before posting.
Try doing a word-search in the standard docs for some words/phrases
taken from your problem statement or from your very carefully worded
"Subject:" header.
Really Really Should
This section describes things that you *really should* do before posting
to clpmisc.
Lurk for a while before posting
This is very important and expected in all newsgroups. Lurking means
to monitor a newsgroup for a period to become familiar with local
customs. Each newsgroup has specific customs and rituals. Knowing
these before you participate will help avoid embarrassing social
situations. Consider yourself to be a foreigner at first!
Search a Usenet archive
There are tens of thousands of Perl programmers. It is very likely
that your question has already been asked (and answered). See if you
can find where it has already been answered.
One such searchable archive is:
http://groups.google.com/advanced_search
If You Like
This section describes things that you *can* do before posting to
clpmisc.
Check Other Resources
You may want to check in books or on web sites to see if you can
find the answer to your question.
But you need to consider the source of such information: there are a
lot of very poor Perl books and web sites, and several good ones
too, of course.
Posting to comp.lang.perl.misc
There can be 200 messages in clpmisc in a single day. Nobody is going to
read every article. They must decide somehow which articles they are
going to read, and which they will skip.
Your post is in competition with 199 other posts. You need to "win"
before a person who can help you will even read your question.
These sections describe how you can help keep your article from being
one of the "skipped" ones.
Is there a better place to ask your question?
Question should be about Perl, not about the application area
It can be difficult to separate out where your problem really is,
but you should make a conscious effort to post to the most
applicable newsgroup. That is, after all, where you are the most
likely to find the people who know how to answer your question.
Being able to "partition" a problem is an essential skill for
effectively troubleshooting programming problems. If you don't get
that right, you end up looking for answers in the wrong places.
It should be understood that you may not know that the root of your
problem is not Perl-related (the two most frequent ones are CGI and
Operating System related), so off-topic postings will happen from
time to time. Be gracious when someone helps you find a better place
to ask your question by pointing you to a more applicable newsgroup.
How to participate (post) in the clpmisc community
Carefully choose the contents of your Subject header
You have 40 precious characters of Subject to win out and be one of
the posts that gets read. Don't waste them. Take care while
composing them, they are the key that opens the door to getting an
answer.
Spend them indicating what aspect of Perl others will find if they
should decide to read your article.
Do not spend them indicating "experience level" (guru, newbie...).
Do not spend them pleading (please read, urgent, help!...).
Do not spend them on non-Subjects (Perl question, one-word
Subject...)
For more information on choosing a Subject see "Choosing Good
Subject Lines":
http://www.cpan.org/authors/id/D/DM/DMR/subjects.post
Part of the beauty of newsgroup dynamics, is that you can contribute
to the community with your very first post! If your choice of
Subject leads a fellow Perler to find the thread you are starting,
then even asking a question helps us all.
Use an effective followup style
When composing a followup, quote only enough text to establish the
context for the comments that you will add. Always indicate who
wrote the quoted material. Never quote an entire article. Never
quote a .signature (unless that is what you are commenting on).
Intersperse your comments *following* each section of quoted text to
which they relate. Unappreciated followup styles are referred to as
"top-posting", "Jeopardy" (because the answer comes before the
question), or "TOFU" (Text Over, Fullquote Under).
Reversing the chronology of the dialog makes it much harder to
understand (some folks won't even read it if written in that style).
For more information on quoting style, see:
http://web.presby.edu/~nnqadmin/nnq/nquote.html
Speak Perl rather than English, when possible
Perl is much more precise than natural language. Saying it in Perl
instead will avoid misunderstanding your question or problem.
Do not say: I have variable with "foo\tbar" in it.
Instead say: I have $var = "foo\tbar", or I have $var = 'foo\tbar',
or I have $var = <DATA> (and show the data line).
Ask perl to help you
You can ask perl itself to help you find common programming mistakes
by doing two things: enable warnings (perldoc warnings) and enable
"strict"ures (perldoc strict).
You should not bother the hundreds/thousands of readers of the
newsgroup without first seeing if a machine can help you find your
problem. It is demeaning to be asked to do the work of a machine. It
will annoy the readers of your article.
You can look up any of the messages that perl might issue to find
out what the message means and how to resolve the potential mistake
(perldoc perldiag). If you would like perl to look them up for you,
you can put "use diagnostics;" near the top of your program.
Do not re-type Perl code
Use copy/paste or your editor's "import" function rather than
attempting to type in your code. If you make a typo you will get
followups about your typos instead of about the question you are
trying to get answered.
Provide enough information
If you do the things in this item, you will have an Extremely Good
chance of getting people to try and help you with your problem!
These features are a really big bonus toward your question winning
out over all of the other posts that you are competing with.
First make a short (less than 20-30 lines) and *complete* program
that illustrates the problem you are having. People should be able
to run your program by copy/pasting the code from your article. (You
will find that doing this step very often reveals your problem
directly. Leading to an answer much more quickly and reliably than
posting to Usenet.)
Describe *precisely* the input to your program. Also provide example
input data for your program. If you need to show file input, use the
__DATA__ token (perldata.pod) to provide the file contents inside of
your Perl program.
Show the output (including the verbatim text of any messages) of
your program.
Describe how you want the output to be different from what you are
getting.
If you have no idea at all of how to code up your situation, be sure
to at least describe the 2 things that you *do* know: input and
desired output.
Do not provide too much information
Do not just post your entire program for debugging. Most especially
do not post someone *else's* entire program.
Do not post binaries, HTML, or MIME
clpmisc is a text only newsgroup. If you have images or binaries
that explain your question, put them in a publically accessible
place (like a Web server) and provide a pointer to that location. If
you include code, cut and paste it directly in the message body.
Don't attach anything to the message. Don't post vcards or HTML.
Many people (and even some Usenet servers) will automatically filter
out such messages. Many people will not be able to easily read your
post. Plain text is something everyone can read.
Social faux pas to avoid
The first two below are symptoms of lots of FAQ asking here in clpmisc.
It happens so often that folks will assume that it is happening yet
again. If you have looked but not found, or found but didn't understand
the docs, say so in your article.
Asking a Frequently Asked Question
It should be understood that you may have missed the applicable FAQ
when you checked, which is not a big deal. But if the Frequently
Asked Question is worded similar to your question, folks will assume
that you did not look at all. Don't become indignant at pointers to
the FAQ, particularly if it solves your problem.
Asking a question easily answered by a cursory doc search
If folks think you have not even tried the obvious step of reading
the docs applicable to your problem, they are likely to become
annoyed.
If you are flamed for not checking when you *did* check, then just
shrug it off (and take the answer that you got).
Asking for emailed answers
Emailed answers benefit one person. Posted answers benefit the
entire community. If folks can take the time to answer your
question, then you can take the time to go get the answer in the
same place where you asked the question.
It is OK to ask for a *copy* of the answer to be emailed, but many
will ignore such requests anyway. If you munge your address, you
should never expect (or ask) to get email in response to a Usenet
post.
Ask the question here, get the answer here (maybe).
Beware of saying "doesn't work"
This is a "red flag" phrase. If you find yourself writing that,
pause and see if you can't describe what is not working without
saying "doesn't work". That is, describe how it is not what you
want.
Sending a "stealth" Cc copy
A "stealth Cc" is when you both email and post a reply without
indicating *in the body* that you are doing so.
Be extra cautious when you get upset
Count to ten before composing a followup when you are upset
This is recommended in all Usenet newsgroups. Here in clpmisc, most
flaming sub-threads are not about any feature of Perl at all! They
are most often for what was seen as a breach of netiquette. If you
have lurked for a bit, then you will know what is expected and won't
make such posts in the first place.
But if you get upset, wait a while before writing your followup. I
recommend waiting at least 30 minutes.
Count to ten after composing and before posting when you are upset
After you have written your followup, wait *another* 30 minutes
before committing yourself by posting it. You cannot take it back
once it has been said.
AUTHOR
Tad McClellan and many others on the comp.lang.perl.misc newsgroup.
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.noitatibaher\100cmdat/"
------------------------------
Date: Fri, 13 Feb 2009 04:49:11 -0800 (PST)
From: K-mart Cashier <cdalten@gmail.com>
Subject: Re: Question about why a pipe doesn't block
Message-Id: <c73a47f1-e573-4258-b502-e76657dd85d1@o2g2000prl.googlegroups.com>
On Feb 12, 3:45 pm, xhos...@gmail.com wrote:
> grocery_stocker <cdal...@gmail.com> wrote:
>
> ...
>
>
>
>
>
> > And the cursor just hangs at the block until I type exit. Now, when I
> > run the 'bbs program' using the following perl script
>
> > m-net% more bbs.pl
> > #!/usr/bin/perl
>
> > use strict;
> > use warnings;
>
> > open my $out, '|-', 'bbs' or die "cannot open pipe to bbs: $!";
>
> > #print $out "browse\n";
>
> > #close $out or die "cannot close pipe to t.exe: $!";
> > m-net% ./bbs.pl
>
> > The program runs and just exits.
>
> ...
>
> > What is causing the script to exit?
>
> It ran out of code to execute. Why wouldn't it exit?
>
> > Even when I uncomment out close ,
> > I still get the exact same behavior
>
> When perl runs out of code to execute, it starts doing the clean-up for
> exit. As part of this, it closes the file handle, even if you didn't
> explicitly request it. After doing so, it probably waits for the child to
> exit, as it was a piped open. The bbs almost instantly sees that its input
> has been closed, so it exits, satisfying Perl's wait so the wait blocks for
> a teeny tiny time. Is this the blocking you were thinking of?
>
> If not, what exactly did you think would block, and where and why do you
> think it would do so?
>
Wait. I forgot why I asked this question. I'm serious. I was going
through some kind of weird sleep deprivation when I did this post.
Later on today, I might remember what I was tryinging to ask, and then
post a followup question.
------------------------------
Date: Fri, 13 Feb 2009 13:58:25 +0100
From: Rainer Weikusat <rweikusat@mssgmbh.com>
Subject: Re: Question about why a pipe doesn't block
Message-Id: <87tz6y4hou.fsf@fever.mssgmbh.com>
WANG Cong <xiyou.wangcong@gmail.com> writes:
> grocery_stocker wrote:
>
>> m-net% more bbs.pl
>> #!/usr/bin/perl
>>
>> use strict;
>> use warnings;
>>
>> open my $out, '|-', 'bbs' or die "cannot open pipe to bbs: $!";
>>
>> #print $out "browse\n";
>>
>> #close $out or die "cannot close pipe to t.exe: $!";
>
> <snip>
>
>> What is causing the script to exit? Even when I uncomment out close ,
>> I still get the exact same behavior
>
> Because your perl program is in the write end of a pipe, why
> should it block?
Waiting for buffer space. But since the program isn't doing anything
except createing a pipe, how can it possibly wait for something to
become available? It will immediately exit, causing the BBS to
receive an EOF indication on its standard input and to subsequently
exit, too.
------------------------------
Date: Fri, 13 Feb 2009 05:20:29 -0800 (PST)
From: emcee2k@gmail.com
Subject: Simple question about binmode
Message-Id: <bb8586e4-b8f7-4f3a-85ab-3a617c6c6bf9@f40g2000pri.googlegroups.com>
When I run the following code, it creates a 1063 byte file on Win32:
open(F, 'textfile.txt');
read(F, $txtPreview, 1024, 0);
close(F);
open(TL, '>textpreview.txt');
print TL $txtPreview;
close(TL);
There's 39 line breaks in the file it creates, so that explains the
file size of 1063 instead of 1024. However, with this code I expected
to get a file of 1024, but I still got 1063:
open(F, 'textfile.txt');
binmode(F);
read(F, $txtPreview, 1024, 0);
close(F);
open(TL, '>textpreview.txt');
print TL $txtPreview;
close(TL);
So what do I have to do to insure that the length argument to the read
function is treated as the amount of bytes to be read, rather than the
amount of characters?
------------------------------
Date: Fri, 13 Feb 2009 14:58:54 +0100
From: Gunnar Hjalmarsson <noreply@gunnar.cc>
Subject: Re: Simple question about binmode
Message-Id: <6vlch7FkihntU1@mid.individual.net>
emcee2k@gmail.com wrote:
> When I run the following code, it creates a 1063 byte file on Win32:
>
> open(F, 'textfile.txt');
> read(F, $txtPreview, 1024, 0);
> close(F);
> open(TL, '>textpreview.txt');
> print TL $txtPreview;
> close(TL);
>
> There's 39 line breaks in the file it creates, so that explains the
> file size of 1063 instead of 1024.
Then textfile.txt is most likely *nix formated.
> However, with this code I expected
> to get a file of 1024, but I still got 1063:
>
> open(F, 'textfile.txt');
> binmode(F);
> read(F, $txtPreview, 1024, 0);
> close(F);
> open(TL, '>textpreview.txt');
> print TL $txtPreview;
> close(TL);
It's TL you need to binmode to prevent Win32 from adding \015 to each line.
> So what do I have to do to insure that the length argument to the read
> function is treated as the amount of bytes to be read, rather than the
> amount of characters?
I don't think your analysis is correct.
--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl
------------------------------
Date: Fri, 13 Feb 2009 07:57:44 -0600
From: Tad J McClellan <tadmc@seesig.invalid>
Subject: Re: Simple question about binmode
Message-Id: <slrngpav2o.71l.tadmc@tadmc30.sbcglobal.net>
emcee2k@gmail.com <emcee2k@gmail.com> wrote:
> with this code I expected
> to get a file of 1024, but I still got 1063:
>
> open(F, 'textfile.txt');
> binmode(F);
> read(F, $txtPreview, 1024, 0);
> close(F);
> open(TL, '>textpreview.txt');
> print TL $txtPreview;
> close(TL);
You have not binmode()ed your output filehandle...
read() has a return value (as does open() and close()).
You should check the return values.
The length() function will tell you the size of $txtPreview.
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.noitatibaher\100cmdat/"
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
Administrivia:
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------------------------------
End of Perl-Users Digest V11 Issue 2208
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