[28281] in Perl-Users-Digest
Perl-Users Digest, Issue: 9645 Volume: 10
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Fri Aug 25 09:05:57 2006
Date: Fri, 25 Aug 2006 06:05:05 -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 Fri, 25 Aug 2006 Volume: 10 Number: 9645
Today's topics:
Re: Calling another cgi program using CGI.pm anno4000@radom.zrz.tu-berlin.de
Descriptive/Prescriptive (was Re: IO::Select::select() <David.Squire@no.spam.from.here.au>
Re: IO::Select::select() says no readable data even if <ced@blv-sam-01.ca.boeing.com>
Re: misc <tadmc@augustmail.com>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@augustmail.com
Prevent multiple instances of a script to launch <sicsicsic@freesurf.ch>
Re: Prevent multiple instances of a script to launch anno4000@radom.zrz.tu-berlin.de
Re: Prevent multiple instances of a script to launch <sicsicsic@freesurf.ch>
Re: Prevent multiple instances of a script to launch anno4000@radom.zrz.tu-berlin.de
Re: Prevent multiple instances of a script to launch <sicsicsic@freesurf.ch>
Re: Prevent multiple instances of a script to launch <rvtol+news@isolution.nl>
Re: regular expression variables under debugger <wlcna@nospam.com>
Re: regular expression variables under debugger <wlcna@nospam.com>
Re: regular expression variables under debugger <nospam-abuse@ilyaz.org>
Re: regular expression variables under debugger <wlcna@nospam.com>
Re: regular expression variables under debugger <tadmc@augustmail.com>
Re: Splitting a string to access a multilevel hash <nobull67@gmail.com>
Re: xslt ? <tadmc@augustmail.com>
Re: xslt ? <tadmc@augustmail.com>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: 25 Aug 2006 09:37:40 GMT
From: anno4000@radom.zrz.tu-berlin.de
Subject: Re: Calling another cgi program using CGI.pm
Message-Id: <4l7un4FmkcuU1@news.dfncis.de>
<xhoster@gmail.com> wrote in comp.lang.perl.misc:
> Tad McClellan <tadmc@augustmail.com> wrote:
> > [ Please do not top-post! }
> >
> > dmedhora@gmail.com <dmedhora@gmail.com> wrote:
> >
> > > Lets say if the index.pl program above validates the user/password
> > > successfully then how do I continue to another html page?
> > > say, continue.pl
> >
> > If continue.pl accepts GET requests, you can issue a "redirect":
> >
> > print "Location: http://www.yoursite.com/cgi-bin/continue.pl\n\n";
>
> But then someone could go bypass the validation page and go directly
> to http://www.yoursite.com/cgi-bin/continue.pl
Right. The CGI script would have to serve the protected data itself,
from sources that are not otherwise accessible from the web. That
could be tricky.
In apache web servers there's the .htaccess mechanism that is designed
(among other things) to add password-protection to pages. That kind of
solution is certainly better than self-made security via CGI.
Anno
------------------------------
Date: Fri, 25 Aug 2006 09:53:28 +0100
From: David Squire <David.Squire@no.spam.from.here.au>
Subject: Descriptive/Prescriptive (was Re: IO::Select::select() says no readable data even if there are)
Message-Id: <ecmdq7$meu$1@gemini.csx.cam.ac.uk>
Charles DeRykus wrote:
> David Squire wrote:
>> ...
>>
>>
>> [1] Still, it's worth knowing what prescriptivists want, so that you can
> ^^^^^^^^^^^^^^
>
> Somehow 'prescribers' seems more reminiscent of those administering
> awful medicine .... :)
>
True, but not a synonym in this case. In grammar-land, the wars rage
between the descriptive and prescriptive schools, and they call
themselves descriptivists and prescriptivists. See
http://en.wikipedia.org/wiki/Prescriptive_grammar
Still, as a descriptivist, I guess I should swallow your 'prescribers'
prescription :)
ObPerl: Perl's flexible syntax makes it perhaps the most
descriptivist-feeling programming language I have used.
------------------------------
Date: Fri, 25 Aug 2006 04:56:05 GMT
From: Charles DeRykus <ced@blv-sam-01.ca.boeing.com>
Subject: Re: IO::Select::select() says no readable data even if there are
Message-Id: <J4JF1F.5t@news.boeing.com>
David Squire wrote:
>...
>
>
> [1] Still, it's worth knowing what prescriptivists want, so that you can
^^^^^^^^^^^^^^
Somehow 'prescribers' seems more reminiscent of those administering
awful medicine .... :)
Forgive me -- no Perl content at all...
--
Charles DeRykus
------------------------------
Date: Thu, 24 Aug 2006 21:49:01 -0500
From: Tad McClellan <tadmc@augustmail.com>
Subject: Re: misc
Message-Id: <slrneesp8t.mcs.tadmc@magna.augustmail.com>
laura.biding@ntlworld.com <laura.biding@ntlworld.com> wrote:
>>
> laura.biding@ntlworld.com
has been plonked.
--
Tad McClellan SGML consulting
tadmc@augustmail.com Perl programming
Fort Worth, Texas
------------------------------
Date: 25 Aug 2006 07:22:13 GMT
From: tadmc@augustmail.com
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.6 $)
Message-Id: <44eea524$0$47255$ae4e5890@news.nationwide.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: 1.6 $)
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.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: Fri, 25 Aug 2006 10:01:56 +0200
From: Philipp <sicsicsic@freesurf.ch>
Subject: Prevent multiple instances of a script to launch
Message-Id: <1156492918_2998@sicinfo3.epfl.ch>
Hello
I have written a Perl script (win32) and use it to drag&drop files on it
for execution.
Now if I drop multiple files at once, they are processed one after the
other. But if I drop one file at a time, each starts a new perl
interpreter and new script.
Is there an easy way to prevent these new copies to start and instead
queue the corresponding files in an already running script? (so they get
executed sequentially and not in parallel)
Thanks for your answers
Phil
------------------------------
Date: 25 Aug 2006 09:02:32 GMT
From: anno4000@radom.zrz.tu-berlin.de
Subject: Re: Prevent multiple instances of a script to launch
Message-Id: <4l7sl8Flte7U1@news.dfncis.de>
Philipp <sicsicsic@freesurf.ch> wrote in comp.lang.perl.misc:
> Hello
> I have written a Perl script (win32) and use it to drag&drop files on it
> for execution.
> Now if I drop multiple files at once, they are processed one after the
> other. But if I drop one file at a time, each starts a new perl
> interpreter and new script.
>
> Is there an easy way to prevent these new copies to start and instead
> queue the corresponding files in an already running script? (so they get
> executed sequentially and not in parallel)
The standard method is for the program to acquire an exclusive lock
on some (fixed) file before starting to work. That serializes the
processes. I don't know how well file locking works on win32.
Anno
------------------------------
Date: Fri, 25 Aug 2006 12:11:18 +0200
From: Philipp <sicsicsic@freesurf.ch>
Subject: Re: Prevent multiple instances of a script to launch
Message-Id: <1156500678_3019@sicinfo3.epfl.ch>
anno4000@radom.zrz.tu-berlin.de wrote:
> Philipp <sicsicsic@freesurf.ch> wrote in comp.lang.perl.misc:
>
>>Hello
>>I have written a Perl script (win32) and use it to drag&drop files on it
>>for execution.
>>Now if I drop multiple files at once, they are processed one after the
>>other. But if I drop one file at a time, each starts a new perl
>>interpreter and new script.
>>
>>Is there an easy way to prevent these new copies to start and instead
>>queue the corresponding files in an already running script? (so they get
>>executed sequentially and not in parallel)
>
>
> The standard method is for the program to acquire an exclusive lock
> on some (fixed) file before starting to work. That serializes the
> processes. I don't know how well file locking works on win32.
If I understand this correctly, this will start a second interpreter but
it will wait until the lock of the first is released? This is not
exactly the behavior that I want.
I would like all files to be processed by the same interpreter instance.
This means that a second instance would need to:
- check somehow if a first one is already running (eg. with a lock?)
- add files to the queue of first instance (how?)
For the second point I can imagine a method like writing a queue to a
file but probably writing to some stack in memory is better/faster. How
could I do this? How can you make two scripts share a piece of memory?
If you could point me to some documentation or even better som existing
code somewhere, I would be very grateful.
Phil
------------------------------
Date: 25 Aug 2006 10:59:25 GMT
From: anno4000@radom.zrz.tu-berlin.de
Subject: Re: Prevent multiple instances of a script to launch
Message-Id: <4l83gdFnfrbU1@news.dfncis.de>
Philipp <sicsicsic@freesurf.ch> wrote in comp.lang.perl.misc:
> anno4000@radom.zrz.tu-berlin.de wrote:
> > Philipp <sicsicsic@freesurf.ch> wrote in comp.lang.perl.misc:
> >
> >>Hello
> >>I have written a Perl script (win32) and use it to drag&drop files on it
> >>for execution.
> >>Now if I drop multiple files at once, they are processed one after the
> >>other. But if I drop one file at a time, each starts a new perl
> >>interpreter and new script.
> >>
> >>Is there an easy way to prevent these new copies to start and instead
> >>queue the corresponding files in an already running script? (so they get
> >>executed sequentially and not in parallel)
> >
> >
> > The standard method is for the program to acquire an exclusive lock
> > on some (fixed) file before starting to work. That serializes the
> > processes. I don't know how well file locking works on win32.
>
> If I understand this correctly, this will start a second interpreter but
> it will wait until the lock of the first is released? This is not
> exactly the behavior that I want.
Right. That's often good enough.
> I would like all files to be processed by the same interpreter instance.
> This means that a second instance would need to:
> - check somehow if a first one is already running (eg. with a lock?)
> - add files to the queue of first instance (how?)
That amounts to a sever-client model. There is a lot of literature
about that (start with perlipc) and lots of CPAN modules that support
that model.
You'll need some form of IPC to transmit requests to the server. The
server could be started on demand and quit when there is nothing to do,
or it could be started once and keep running (other possibilities exist).
Again, file locking is the safest way of keeping multiple instances
of the server from running, but the server doesn't wait for the lock,
it tests the lock non-blocking and just quits when it can't get it.
Anno
------------------------------
Date: Fri, 25 Aug 2006 13:48:56 +0200
From: Philipp <sicsicsic@freesurf.ch>
Subject: Re: Prevent multiple instances of a script to launch
Message-Id: <1156506536_3037@sicinfo3.epfl.ch>
anno4000@radom.zrz.tu-berlin.de wrote:
> That amounts to a sever-client model. There is a lot of literature
> about that (start with perlipc) and lots of CPAN modules that support
> that model.
>
> You'll need some form of IPC to transmit requests to the server. The
> server could be started on demand and quit when there is nothing to do,
> or it could be started once and keep running (other possibilities exist).
> Again, file locking is the safest way of keeping multiple instances
> of the server from running, but the server doesn't wait for the lock,
> it tests the lock non-blocking and just quits when it can't get it.
OK thanks. I will look into that (although it looks way out of my
programming skills...)
Phil
------------------------------
Date: Fri, 25 Aug 2006 14:16:03 +0200
From: "Dr.Ruud" <rvtol+news@isolution.nl>
Subject: Re: Prevent multiple instances of a script to launch
Message-Id: <ecn0no.168.1@news.isolution.nl>
Philipp schreef:
> I have written a Perl script (win32) and use it to drag&drop files on
> it for execution.
> Now if I drop multiple files at once, they are processed one after the
> other. But if I drop one file at a time, each starts a new perl
> interpreter and new script.
>
> Is there an easy way to prevent these new copies to start and instead
> queue the corresponding files in an already running script? (so they
> get executed sequentially and not in parallel)
The new copy should check whether there is an older copy running, and
then hand over its job-data to that older copy. You could use POE.
--
Affijn, Ruud
"Gewoon is een tijger."
------------------------------
Date: Fri, 25 Aug 2006 06:17:42 GMT
From: "wlcna" <wlcna@nospam.com>
Subject: Re: regular expression variables under debugger
Message-Id: <aCwHg.10901$%j7.6279@newssvr29.news.prodigy.net>
"wlcna" <wlcna@nospam.com> wrote in message
news:PwpHg.455$Cq4.290@newssvr25.news.prodigy.net...
> Well, you (and the other who said this shouldn't be happening) are
> right about the example I provided - it does not show the behavior I'm
> describing though it is essentially the same code where I do see the
OK, I have some new and improved information here.
I've confirmed that the behavior IS DIFFERENT under the debugger versus
not under the debugger as I originally stated. I.e. a Heisenberg
problem! The debugger is causing the problem that I am viewing!
I confirmed this via print statements again. I have a "sub" that gets
an argument that comes from the parsing of this regular expression (and
from the $1 result of such parsing as shown in the sample code) and
under the debugger, this sub bombs the program via a "die" statement b/c
I added a check of the argument to make sure it's a value and not undef.
But if I run the program not under the debugger, the print statement
shows the proper number and runs along without any weirdness.
Also, I took the suggestion of one of the guys out here and put a watch
on $1, and I noticed a bunch of utf8 stuff happening when the line of
regex code in question was evaluated. This utf8 stuff was shown b/c
apparently $1 was getting modified, modified to "#" I have no idea why
and then modified to undef, again no idea there either. There was no
"#" anywhere in the string being regexed.
And when I run this in the tester program I posted, there is no such
utf8 weirdness. Additionally, I also tried putting identical values and
identical regex (via copy and paste) into that tester program, no utf8
weirdness occurs. I think I'm onto some weirdness there eh?
As I say the code in question is virtually identical to what I posted,
the only difference is the libraries etc. being loaded and used it seems
to me, obviously there's more going on in the other code.
But here's the actual line of code that triggers this utf thing:
$str =~ /([0-9]*)\.html/;
And here's what this utf weirdness looks like in the debugger:
main::(MYPROGRAMNAMEHERE:102): $str =~
/([0-9]*)\.html/;
DB<4>
Watchpoint 0: $1 changed:
old value: ''
new value: '#'
utf8::SWASHNEW(/usr/local/perl/lib/5.8.2/utf8_heavy.pl:203):
203: my $char = $1;
DB<4>
The "$str" is of the form: http://asite.aplace.org/adir/22221.html
Anyone have any opinions? I'm now thinking it has something to do with
these HTML/XML parsing libraries for some reason. As I say, I use these
alot and I have always had issues with reading these regular expression
variables while in debug mode.
I think I've got a theory: The characters coming back from this web
page via the XML::Parser library are in UTF8 and this is some weirdness
connected to that.
What do people think? Why does this weirdness only happen under the
debugger?
------------------------------
Date: Fri, 25 Aug 2006 06:19:18 GMT
From: "wlcna" <wlcna@nospam.com>
Subject: Re: regular expression variables under debugger
Message-Id: <GDwHg.10902$%j7.1262@newssvr29.news.prodigy.net>
"Dr.Ruud" <rvtol+news@isolution.nl> wrote in message
news:eck6nj.1ps.1@news.isolution.nl...
> For me it works (with -d) as you expect.
> Did you also try to add watch expressions with -w for $str and $1?
>
So, I thought putting a watch on $1 was a useful suggestion - I took
that suggestion. Please see my response in the other part of the
thread!
------------------------------
Date: Fri, 25 Aug 2006 08:27:27 +0000 (UTC)
From: Ilya Zakharevich <nospam-abuse@ilyaz.org>
Subject: Re: regular expression variables under debugger
Message-Id: <ecmc9f$1cof$1@agate.berkeley.edu>
[A complimentary Cc of this posting was sent to
wlcna
<wlcna@nospam.com>], who wrote in article <aCwHg.10901$%j7.6279@newssvr29.news.prodigy.net>:
> "wlcna" <wlcna@nospam.com> wrote in message
> news:PwpHg.455$Cq4.290@newssvr25.news.prodigy.net...
> I've confirmed that the behavior IS DIFFERENT under the debugger versus
> not under the debugger as I originally stated. I.e. a Heisenberg
> problem! The debugger is causing the problem that I am viewing!
No wonder. What you see is a bug; running under debugger causes
different code paths, so different bugs show...
the most crucial info is your perl -V. Why did not you post it yet?
If you are not running the latest released version of Perl, you must
recheck with the newer version. If it is the latest, nothing/nobody
would help you until you can provide a minimal possible script which
demonstrates the same problem
Hope this helps,
Ilya
------------------------------
Date: Fri, 25 Aug 2006 12:19:38 GMT
From: "wlcna" <wlcna@nospam.com>
Subject: Re: regular expression variables under debugger
Message-Id: <uVBHg.2885$yO7.2713@newssvr14.news.prodigy.com>
"Ilya Zakharevich" <nospam-abuse@ilyaz.org> wrote in message
news:ecmc9f$1cof$1@agate.berkeley.edu...
> No wonder. What you see is a bug; running under debugger causes
> different code paths, so different bugs show...
>
> the most crucial info is your perl -V. Why did not you post it yet?
>
5.8.2 is the version.
Re: getting the latest, is there a way to update perl without losing all
the libraries that are installed? Can you give me a tip on dealing with
this issue? I compile my own perl (under Linux)...
> If you are not running the latest released version of Perl, you must
> recheck with the newer version. If it is the latest, nothing/nobody
> would help you until you can provide a minimal possible script which
> demonstrates the same problem
>
> Hope this helps,
> Ilya
------------------------------
Date: Thu, 24 Aug 2006 21:47:15 -0500
From: Tad McClellan <tadmc@augustmail.com>
Subject: Re: regular expression variables under debugger
Message-Id: <slrneesp5j.mcs.tadmc@magna.augustmail.com>
wlcna <wlcna@nospam.com> wrote:
> "Xicheng Jia" <xicheng@gmail.com> wrote in message
> news:1156419627.585589.49800@h48g2000cwc.googlegroups.com...
>> main::(t1.pl:5): my $str = "hello there yes i am here";
>> DB<1> n
>> main::(t1.pl:6): $str =~ /([a-z]*)s/;
>> DB<1> n
>> main::(t1.pl:7): $yes = $1;
>> DB<2> x $1
> Well, you (and the other who said this shouldn't be happening) are right
> about the example I provided - it does not show the behavior I'm
> describing though it is essentially the same code where I do see the
^^^^^^^^^^^^^^^^^^^^
> issue!!
Then the problem is probably in the part that made you use
the "essentially" qualifier... :-)
> I'm using via copy/paste inside the bugger, evaluating something like
> $str =~ /([a-z]*)s/; print $1; and the $1 comes through in that
> scenario.
>
> I don't foreclose the possibility that there might be something here I'm
> just clueless about.
I have a guess that might explain what you see.
You have now _twice_ posted code that uses a dollar-digit variable
without first ensuring that the intended pattern match _succeeded_.
If the match you intended to set $1 fails, then the value you see
for $1 is some old stale value from a previous match that _did_
succeed (or undef if no successful matches).
--
Tad McClellan SGML consulting
tadmc@augustmail.com Perl programming
Fort Worth, Texas
------------------------------
Date: 25 Aug 2006 04:05:23 -0700
From: "Brian McCauley" <nobull67@gmail.com>
Subject: Re: Splitting a string to access a multilevel hash
Message-Id: <1156503923.371563.293490@m79g2000cwm.googlegroups.com>
wolfram.humann wrote:
> So I think I will stick to my original idea, stuff it into a sub like this:
>
> sub resolve
> {
> my ($tmp, $path) = @_;
> $tmp = $tmp->{$_} for split '\.', $path;
> return $tmp;
> }
Sooner or later you'll probably wish you'd written that as an lvalue
sub
sub resolve : lvalue
{
my $tmp = \shift;
$tmp = \$$tmp->{$_} for split '\.', shift;
$$tmp;
}
------------------------------
Date: Thu, 24 Aug 2006 21:37:27 -0500
From: Tad McClellan <tadmc@augustmail.com>
Subject: Re: xslt ?
Message-Id: <slrneesoj7.mcs.tadmc@magna.augustmail.com>
surf <surfunbear@yahoo.com> wrote:
>
> Matt Garrish wrote:
>> surf wrote:
>>
>> > I had tried to work with XLST a few years ago. I got some simple stuff
>> > to work, then I started playing with perl XML parsers and the xml:twig
>> > module in perl. All of this stuff I really liked, so I forgot about
>> > working with xlst which to me didn't seem like the way to go,
>> > especially if it got very complex. I'm not sure why anyone would want
>> > to write a program of any sort in XML anyway ?
>> >
>>
>> You're so behind the times. Everyone is using RXParse for their XML
>> these days. Be sure and tell your recruiter.
>>
>> Matt
>
> Under jobs on boston craigslist I searched for xslt and got 222 hits,
> I got none for RXParse. That doesn't mean it isn't great, just that no
> one in boston is looking to hire anyone based on that unless it's a
> tool that is part of some other application.
Matt's post was an (inside) joke. He should have put a smiley in it.
RXParse is an abomination of a hack, written by a troll that
posts here from time to time.
I wouldn't mention it to a recruiter. :-)
--
Tad McClellan SGML consulting
tadmc@augustmail.com Perl programming
Fort Worth, Texas
------------------------------
Date: Thu, 24 Aug 2006 21:40:36 -0500
From: Tad McClellan <tadmc@augustmail.com>
Subject: Re: xslt ?
Message-Id: <slrneesop4.mcs.tadmc@magna.augustmail.com>
surf <surfunbear@yahoo.com> wrote:
>
> Tad McClellan wrote:
>> surf <surfunbear@yahoo.com> wrote:
>>
>>
>> > I'm not sure why anyone would want
>> > to write a program of any sort in XML anyway ?
>>
>>
>> One Reason:
>>
>> XSLT is optimized for machines rather than for humans.
>>
>>
>>
>> Let's haul this back on-topic:
>>
>> Contrast that with Perl, which is optimized for humans at the
>> expense of the machine (throwing cycles and memory at a problem).
>>
>>
>
> I'm not an xslt expert, but you need to elaborate on that.
^^^^
^^^^
No I don't.
> Obviously
> programming in assembly language is not very popular, although it might
> be optimized for machines.
I don't need to elaborate on what I said.
I might need to elaborate on why XSLT is popular though.
Here's my stab at it: platform independence.
--
Tad McClellan SGML consulting
tadmc@augustmail.com Perl programming
Fort Worth, Texas
------------------------------
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:
#The Perl-Users Digest is a retransmission of the USENET newsgroup
#comp.lang.perl.misc. For subscription or unsubscription requests, send
#the single line:
#
# subscribe perl-users
#or:
# unsubscribe perl-users
#
#to almanac@ruby.oce.orst.edu.
NOTE: due to the current flood of worm email banging on ruby, the smtp
server on ruby has been shut off until further notice.
To submit articles to comp.lang.perl.announce, send your article to
clpa@perl.com.
#To request back copies (available for a week or so), send your request
#to almanac@ruby.oce.orst.edu with the command "send perl-users x.y",
#where x is the volume number and y is the issue number.
#For other requests pertaining to the digest, send mail to
#perl-users-request@ruby.oce.orst.edu. Do not waste your time or mine
#sending perl questions to the -request address, I don't have time to
#answer them even if I did know the answer.
------------------------------
End of Perl-Users Digest V10 Issue 9645
***************************************
