[24960] in Perl-Users-Digest
Perl-Users Digest, Issue: 7210 Volume: 10
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue Oct 5 06:06:53 2004
Date: Tue, 5 Oct 2004 03:05:04 -0700 (PDT)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Tue, 5 Oct 2004 Volume: 10 Number: 7210
Today's topics:
Re: Building a Perl based online survey and data gather <abigail@abigail.nl>
Re: Building a Perl based online survey and data gather <matrix_calling@yahoo.dot.com>
Re: Can perl SHA1 module be applied to files? <kuujinbo@hotmail.com>
Re: Perl6 <abigail@abigail.nl>
Re: Perl6 <nospam@bigpond.com>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@augustmail.com
Re: regex error <bcaligari@nospam.fireforged.com>
Re: regex error <bcaligari@nospam.fireforged.com>
Re: Regular Expression help please <deja_nospam_@zaft.com>
Re: Regular Expression help please (Anno Siegel)
Re: Which Counter is Perfect? <abigail@abigail.nl>
Re: Which Counter is Perfect? <nntp@rogers.com>
Re: Which Counter is Perfect? <sholden@flexal.cs.usyd.edu.au>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: 05 Oct 2004 07:22:37 GMT
From: Abigail <abigail@abigail.nl>
Subject: Re: Building a Perl based online survey and data gathering, reporting and analysis tool
Message-Id: <slrncm4itt.qgs.abigail@alexandra.abigail.nl>
George_V (George.Vidalis@its.monash.edu.au) wrote on MMMMLIII September
MCMXCIII in <URL:news:cd616041.0410042253.54a74c1a@posting.google.com>:
-- Hi all. First up - I'm not a programmer. I'm researching for an online
-- survey and data analysis tool for Monash University, Australia.
--
-- Our developers are keen on a Perl solution. I've found some Perl form
-- generators and basic survey tools, but we need something that has
-- powerful gathering, reporting and analysis capability.
--
-- I have included a wish list of our requirements, hopefully they'll
-- make enough sense to give you an idea of what we're after. If anyone
-- knows of a single Perl based package or any useful modules that could
-- be added onto a front end to build a complete package I would be most
-- grateful for your info.
If you are looking for a canned solution, why does the language it's
written in matter?
Nevertheless, this group is about the programming language Perl. Not
about software that happens to be written in Perl. If you would program
whatever you need in Perl yourself, and have any questions, feel free
to ask.
Abigail
--
perl -Mstrict -we '$_ = "goto _.print chop;\n=rekcaH lreP rehtona tsuJ";_1:eval'
------------------------------
Date: Tue, 05 Oct 2004 14:06:42 +0530
From: Abhinav <matrix_calling@yahoo.dot.com>
Subject: Re: Building a Perl based online survey and data gathering, reporting and analysis tool
Message-Id: <pdt8d.10$wi.31@news.oracle.com>
George_V wrote:
> Hi all. First up - I'm not a programmer. I'm researching for an online
> survey and data analysis tool for Monash University, Australia.
>
> Our developers are keen on a Perl solution. I've found some Perl form
> generators and basic survey tools, but we need something that has
> powerful gathering, reporting and analysis capability.
>
> I have included a wish list of our requirements, hopefully they'll
> make enough sense to give you an idea of what we're after. If anyone
> knows of a single Perl based package or any useful modules that could
> be added onto a front end to build a complete package I would be most
> grateful for your info.
>
[Snipped Wishlist]
There are many web sites which host such surveys, as I found out while
doing a [small] project of this kind a few years back.
Searching google will bring up most of them..
Regards
Abhinav
------------------------------
Date: Tue, 05 Oct 2004 16:32:46 +0900
From: ko <kuujinbo@hotmail.com>
Subject: Re: Can perl SHA1 module be applied to files?
Message-Id: <2sf10rF1j4bslU1@uni-berlin.de>
Lee Hibberd wrote:
> Hello all
>
> I have used sha1_file in php and want to know if there is an
> equivalent in perl. i.e. I want to produce a sha1 value based on the
> composition of the file and not the filename. I have used the perl
> sha1 digest, but I'm unsure if this is working correctly. One reason
> for my uncertainty is that the sha1 values produced by php sha1_file
> differ. The second reason is I guess I would need to feed the
> bit-stream through the sha1 in perl as if it were a line of text, and
> I'm not sure that my code does that:
>
> my $fn="$file";
> my $fh = new IO::File;
> $fh->open($fn) or @row = $dbh->do( "
> UPDATE All_Locations SET SHA1Date = Date(),SHA1Time =
> Time(),ErrorCode=\'NoFile\' WHERE FileID=$row[0]
> " );
> $digest = new Digest::SHA1;
> $digest->addfile($fh);
> $fh->close;
> $sha1var = $digest->hexdigest;
> print $file.": ".$sha1var."\n";
>
> Any help would be greatly appreciated.
>
> Lee Hibberd
> National Library of Scotland
The documentation for addfile() states that the filehandle should be in
binmode:
use Digest::SHA1;
open my $fh, shift or die $!;
binmode($fh);
print Digest::SHA1->new->addfile($fh)->hexdigest, "\n";
close $fh;
Digest::MD5 has an interface similar to Digest::SHA1 and example code
you might want to look at.
HTH - keith
------------------------------
Date: 05 Oct 2004 07:07:17 GMT
From: Abigail <abigail@abigail.nl>
Subject: Re: Perl6
Message-Id: <slrncm4i15.qgs.abigail@alexandra.abigail.nl>
Polu Kiran (polu.kiran@gmail.com) wrote on MMMMLIII September MCMXCIII in
<URL:news:dde30c8c.0410042239.7c7630bf@posting.google.com>:
&& Hi,
&&
&& Does anybody knows the difference between perl5 and perl6?
Perl5 exists, is actively maintained, and sees a new release every 3 months.
Perl6 doesn't exist, has been marketed as the best thing since sliced
bread for over 4 years now, and sees one design document per year.
Abigail
--
# Perl 5.6.0 broke this.
%0=map{reverse+chop,$_}ABC,ACB,BAC,BCA,CAB,CBA;$_=shift().AC;1while+s/(\d+)((.)
(.))/($0=$1-1)?"$0$3$0{$2}1$2$0$0{$2}$4":"$3 => $4\n"/xeg;print#Towers of Hanoi
------------------------------
Date: Tue, 05 Oct 2004 18:34:26 +1000
From: Gregory Toomey <nospam@bigpond.com>
Subject: Re: Perl6
Message-Id: <2sf4kjF1jovcvU1@uni-berlin.de>
Polu Kiran wrote:
> Hi,
>
> Does anybody knows the difference between perl5 and perl6?
>
> advance thanx.
Its due for release when George Bush finds a weapon of mass destruction in
Iraq! See http://dev.perl.org/perl6/exegesis/
Over 100 operators, every paradigm known to computer science, Perl 6 has it
all ...
gtoomey
------------------------------
Date: Tue, 05 Oct 2004 02:23:02 -0500
From: tadmc@augustmail.com
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.5 $)
Message-Id: <vpudnYPUK51L1v_cRVn-tA@august.net>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($Revision: 1.5 $)
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://mail.augustmail.com/~tadmc/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
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_group_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 <tadmc@augustmail.com> and many others on the
comp.lang.perl.misc newsgroup.
------------------------------
Date: Tue, 05 Oct 2004 07:58:30 +0000
From: Brendon Caligari <bcaligari@nospam.fireforged.com>
Subject: Re: regex error
Message-Id: <41625427$0$94917$bed64819@news.gradwell.net>
Bob Walton wrote:
> Brendon Caligari wrote:
>
>> Abigail wrote:
>>
>>> Brendon Caligari (bcaligari@nospam.fireforged.com) wrote on MMMMLII
>>> September MCMXCIII in
<snip>
> Always *always* before using a "number variable", check to see if the
> match succeeded. Maybe like:
>
> if($str=~m/^length: (\d+?)$/ms){
> $num=$1;
> }
> else{
> die "Bad length: line";
> }
>
>> $num = $1;
>> $str =~ m/^data: '(.{$num})'$/ms;
>
>
> Again, before using $1 from this statement, check to see if the match
> was successful. Another way:
This code was not meant to be 'proper' ..but to expose the panic
situation. The original script was longer but i reduced it to the
shortest i could where it would still 'panic'.
------------------------------
Date: Tue, 05 Oct 2004 08:18:23 +0000
From: Brendon Caligari <bcaligari@nospam.fireforged.com>
Subject: Re: regex error
Message-Id: <416258d1$0$94918$bed64819@news.gradwell.net>
Abigail wrote:
<snip>
>
>
> It might be a bug in Perl. Could you make a self-contained program that
> exhibits this bug?
>
That is EXACTLY what the earlier posted script and other file does.
I shortened the script as much as possible that while it makes no sense
whatsoever it should be syntactically correct but still 'panics'.
If I include the contents of the associated data file 'x' directly into
the variable the script does NOT panic.
Anyhows...my conclusion is that this WAS a Perl bug...one that's been
fixed a while ago. Red Hat ES seem to ship a pretty oldish Perl. I
installed a newer release and all worked as expected.
B.
------------------------------
Date: Tue, 5 Oct 2004 00:53:40 -0700
From: "ZafT" <deja_nospam_@zaft.com>
Subject: Re: Regular Expression help please
Message-Id: <0-udnc9ioNSfzv_cRVn-og@comcast.com>
>
> Asking on Usenet, and bothering hundreds of other people just to avoid
> writing a one-liner in Perl, now *that* is overkill.
>
First of all, you don't have to read the frickin post. I tried to ask
nicely, as I didn't know where elso to go, and groveled at the group's feet
for mercy to avoid getting flamed.
Second, how much of a bother is it to post a message. Hundreds? I think
not. If so, then you just bothered the same group of people by posting a
reply- a senseless one I might add. At least I really needed some help.
Now I just had to bother them all over again just to bitch at you.
Third, i just didn't have a perl interpreter (and can't install one without
nazis breaking down my door) on that box and am not allowed ftp, ssh, or
telnet access from where I posted from. I really thought that it would be
an easy one to figure out. I mean, really - if there's a group of people
that use regular expressions a lot, here they are. Any other group would
give me a blank stare. I may have picked the wrong group, but not the wrong
group of people.
I do want to thank those of you who tactfully pointed me in the right
direction and gave me bits of code. To the HUNDREDS of others that I
bothered - sorry. To Abigail - I truly hope you find something better to do
with your time that to pick on people asking for help.
Shane
------------------------------
Date: 5 Oct 2004 09:54:30 GMT
From: anno4000@lublin.zrz.tu-berlin.de (Anno Siegel)
Subject: Re: Regular Expression help please
Message-Id: <cjtr0m$ead$1@mamenchi.zrz.TU-Berlin.DE>
ZafT <deja_nospam_@zaft.com> wrote in comp.lang.perl.misc:
>
> >
> > Asking on Usenet, and bothering hundreds of other people just to avoid
> > writing a one-liner in Perl, now *that* is overkill.
> >
>
> First of all, you don't have to read the frickin post.
Sure we do, at least to the point where it's clear that it is
off topic.
> I tried to ask
> nicely, as I didn't know where elso to go, and groveled at the group's feet
> for mercy to avoid getting flamed.
Well, you failed. groveling-in-advance doesn't make you immune.
> Second, how much of a bother is it to post a message. Hundreds? I think
> not. If so, then you just bothered the same group of people by posting a
> reply- a senseless one I might add. At least I really needed some help.
> Now I just had to bother them all over again just to bitch at you.
Had to, eh? You could have gracefully conceded your error.
> Third, i just didn't have a perl interpreter (and can't install one without
> nazis breaking down my door) on that box and am not allowed ftp, ssh, or
> telnet access from where I posted from.
So your miserable conditions entitle you to off-topic postings? Not so.
> I really thought that it would be
> an easy one to figure out. I mean, really - if there's a group of people
> that use regular expressions a lot, here they are. Any other group would
> give me a blank stare.
What you essentially asked was, I know how to do it in Perl, how can I
do it in TextPad (or whatever). That got you blank stares. Amazed?
Anno
------------------------------
Date: 05 Oct 2004 07:20:01 GMT
From: Abigail <abigail@abigail.nl>
Subject: Re: Which Counter is Perfect?
Message-Id: <slrncm4ip1.qgs.abigail@alexandra.abigail.nl>
nntp (nntp@rogers.com) wrote on MMMMLIII September MCMXCIII in
<URL:news:D4udnWXfyowKpP_cRVn-vg@rogers.com>:
:) > The second one is simply madness. Why use a seperate lock file when
:) > the counter file will do? Why open a file in read-write mode when you
:) > are only writing to it?
:) >
:) > It also fails to protect the count if the flock fails and hence
:) > can't be called "perfect".
:) >
:) > The second one has far more flaws than the first.
:) >
:) > Please post code in a readable format and not the gunk that is quoted
:) above.
:) >
:) > --
:) > Sam Holden
:)
:) You need to read http://www.perlguy.com/articles/locking.html
:) to understand why the second one is perfect, as far as it stated. I am not
:) an expert, but his statement makes sense.
That article never claims the counter found in perldoc is wrong.
The second isn't perfect at all. It fails to work if the flock fails
(and that's possible!). Furthermore, it only patches one of the silly
things of the base program he starts with, instead of removing it all
together. His basic program opens the data file twice - once for reading,
once for writing. That's not necessary at all, and instead of fixing it
by not doing it, he just patches around it.
Abigail
--
BEGIN {$^H {join "" => ("a" .. "z") [8, 13, 19, 4, 6, 4, 17]} = sub
{["", "Just ", "another ", "Perl ", "Hacker\n"] -> [shift]};
$^H = hex join "" => reverse map {int ($_ / 2)} 0 .. 4}
print 1, 2, 3, 4;
------------------------------
Date: Tue, 5 Oct 2004 04:19:39 -0400
From: "nntp" <nntp@rogers.com>
Subject: Re: Which Counter is Perfect?
Message-Id: <9MydnS0BYoelxP_cRVn-qQ@rogers.com>
> :)
> :) You need to read http://www.perlguy.com/articles/locking.html
> :) to understand why the second one is perfect, as far as it stated. I am
not
> :) an expert, but his statement makes sense.
>
> That article never claims the counter found in perldoc is wrong.
>
> The second isn't perfect at all. It fails to work if the flock fails
> (and that's possible!). Furthermore, it only patches one of the silly
> things of the base program he starts with, instead of removing it all
> together. His basic program opens the data file twice - once for reading,
> once for writing. That's not necessary at all, and instead of fixing it
> by not doing it, he just patches around it.
>
>
> Abigail
Do you claim that the counter in Perldoc is Perfect? Do you see it covers
all cases?
sysopen(FH, "numfile", O_RDWR|O_CREAT);
flock(FH, LOCK_EX);
$num = <FH> || 0;
seek(FH, 0, 0) ;
truncate(FH, 0);
(print FH $num+1, "\n");
close FH;
I can not see how it can write and read at the same time. I don't understand
why it use sysopen, not open +<;
------------------------------
Date: 5 Oct 2004 08:35:48 GMT
From: Sam Holden <sholden@flexal.cs.usyd.edu.au>
Subject: Re: Which Counter is Perfect?
Message-Id: <slrncm4n74.d4t.sholden@flexal.cs.usyd.edu.au>
On Tue, 5 Oct 2004 04:19:39 -0400, nntp <nntp@rogers.com> wrote:
>> :)
>> :) You need to read http://www.perlguy.com/articles/locking.html
>> :) to understand why the second one is perfect, as far as it stated. I am
> not
>> :) an expert, but his statement makes sense.
>>
>> That article never claims the counter found in perldoc is wrong.
>>
>> The second isn't perfect at all. It fails to work if the flock fails
>> (and that's possible!). Furthermore, it only patches one of the silly
>> things of the base program he starts with, instead of removing it all
>> together. His basic program opens the data file twice - once for reading,
>> once for writing. That's not necessary at all, and instead of fixing it
>> by not doing it, he just patches around it.
>>
>>
>> Abigail
>
> Do you claim that the counter in Perldoc is Perfect? Do you see it covers
> all cases?
It's unlikely to be perfect. In a world of TIMTOWTDI and people of
differing opinions "perfection" is next to impossible.
It's a much better solution for the problem at hand than the code on
that web site. The version that doesn't have the error checking removed
covers all the cases, where "all" is restricted to "I want to increment a
count in a text file".
>
> sysopen(FH, "numfile", O_RDWR|O_CREAT);
> flock(FH, LOCK_EX);
> $num = <FH> || 0;
> seek(FH, 0, 0) ;
> truncate(FH, 0);
> (print FH $num+1, "\n");
> close FH;
>
> I can not see how it can write and read at the same time. I don't understand
> why it use sysopen, not open +<;
O_RDWR means read and write access. A simple perldoc -f sysopen would tell
you that.
The sysopen() version works if the file doesn't exist, whereas the open()
version will fail. Whether that is a good thing or a bad thing will depend
on the situation (see the "perfection" garbage above). I'd say in most
cases it's a good thing and useful for sample code as it will "just work".
--
Sam Holden
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
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Subject: Digest Administrivia (Last modified: 6 Apr 01)
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