[31545] in Perl-Users-Digest
Perl-Users Digest, Issue: 2804 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Fri Feb 5 14:09:32 2010
Date: Fri, 5 Feb 2010 11:09:15 -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, 5 Feb 2010 Volume: 11 Number: 2804
Today's topics:
Re: activestate perlex: is it real? <Phred@example.invalid>
capturing multiple patterns per line <cartercc@gmail.com>
Re: capturing multiple patterns per line <jurgenex@hotmail.com>
Re: capturing multiple patterns per line <cartercc@gmail.com>
Re: capturing multiple patterns per line <willem@stack.nl>
Re: capturing multiple patterns per line <cartercc@gmail.com>
Re: capturing multiple patterns per line <tadmc@seesig.invalid>
Re: capturing multiple patterns per line <someone@example.com>
Re: capturing multiple patterns per line <jurgenex@hotmail.com>
Re: capturing multiple patterns per line <RedGrittyBrick@spamweary.invalid>
Re: function within qq{} <Peter@PSDT.com>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@seesig.invalid
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Fri, 05 Feb 2010 04:09:23 -0700
From: Phred Phungus <Phred@example.invalid>
Subject: Re: activestate perlex: is it real?
Message-Id: <7t2cj3F97cU1@mid.individual.net>
Ben Morrow wrote:
> Quoth fergus@twig-me-uk.not.here (Fergus McMenemie):
>> Ron Bergin <rkb@i.frys.com> wrote:
>>
>>>> discontinued.
>>>>
>>>> Is this true? What is its status?
>>>>
>>> I have not used perlex, but if the official mailing list is any
>>> indication, it would appear to be dead. The last posting to the
>>> mailing list was mid 2007.
>>>
>>> http://aspn.activestate.com/ASPN/Mail/Browse/Threaded/perlex
>> Thanks for that. But there is definetly some FUD at work. After all
>> I came across this today:-
>>
>> http://docs.activestate.com/activeperl/5.10/PerlEx/Welcome.html
>>
>> which has a copyright in the footer of 2009! Now 5.10 only arrived
>> in late 2007.
>
> Almost certainly the docs were all regenerated, and the copyright year
> updated, when ActiveState rolled their release of 5.10.1 (which was
> itself released in August 2009).
>
>>>> I am running perl v5.6.1 on vista sp 2
>>> IMO, that's a bigger problem.
>>>
>>> You should upgrade to at the very least 5.8 or preferably 5.10.
>> If only it were my choice!
>
> You should point out to whoever makes that choice that both 5.6 and 5.8
> are considered end-of-life and completely unsupported by p5p, and that
> most CPAN authors are moving to a minimum supported perl version of
> 5.8.1. Any security holes in 5.6 or the modules you have for 5.6 will
> likely never be fixed, and if there are any issues with Vista (and I
> wouldn't be surprised if there were) they will also never be fixed.
>
> Ben
>
It's so nice to be able to post from a platform that is *not*
activestate. It's a fantastic tool for windows.
--
fred
------------------------------
Date: Fri, 5 Feb 2010 08:17:05 -0800 (PST)
From: ccc31807 <cartercc@gmail.com>
Subject: capturing multiple patterns per line
Message-Id: <98d4c070-4646-467c-8879-f7bf0ddcddc1@u9g2000yqb.googlegroups.com>
This is a newbie question, I admit, but I don't know the answer.
Suppose I am parsing a file line by line, and I want to push to an
array all substrings on that line that match a pattern. For example,
consider the listing below. @urls SHOULD contain this: @urls = (http://
google.com, http://yahoo.com, http://amazon.com, http://ebay.com)
Instead, it contains only the last value. Using the g modifier doesn't
help.
I know why @urls contains only the last value, but I don't know how to
get all the values.
Thanks, CC.
-------listing---------------
use strict;
use warnings;
my @urls;
while (<DATA>)
{
if (/<a.*href="([^"]+)/) { push @urls, $1; }
}
print @urls;
exit(0);
__DATA__
<html>\n
<body>\n
<h1>My Favorite Sites</h1>\n
<p>\n
My favorite sites are <a href="http://google.com">Google</a>, <a
href="http://yahoo.com">Yahoo</a>, <a href="http://amazon.com">Amazon</
a>, and <a href="http://ebay.com">Ebay</a>.\n
</p>\n
</body>\n
</html>\n
------------------------------
Date: Fri, 05 Feb 2010 08:30:39 -0800
From: Jürgen Exner <jurgenex@hotmail.com>
Subject: Re: capturing multiple patterns per line
Message-Id: <vphom59tguiu62vlv920soq7sd77jgd2vb@4ax.com>
ccc31807 <cartercc@gmail.com> wrote:
>This is a newbie question, I admit, but I don't know the answer.
>
>Suppose I am parsing a file line by line, and I want to push to an
>array all substrings on that line that match a pattern. For example,
>consider the listing below. @urls SHOULD contain this: @urls = (http://
>google.com, http://yahoo.com, http://amazon.com, http://ebay.com)
>Instead, it contains only the last value. Using the g modifier doesn't
>help.
>
>I know why @urls contains only the last value, but I don't know how to
>get all the values.
Cannot repro your problem. The code you posted adds all three URLs to
the array and prints them in one contiguous line.
C:\tmp>t.pl
http://google.comhttp://amazon.comhttp://ebay.com
jue
------------------------------
Date: Fri, 5 Feb 2010 08:56:28 -0800 (PST)
From: ccc31807 <cartercc@gmail.com>
Subject: Re: capturing multiple patterns per line
Message-Id: <01e58eff-c503-419e-ab28-0728e2ccc8c0@h2g2000yqj.googlegroups.com>
On Feb 5, 11:30=A0am, J=FCrgen Exner <jurge...@hotmail.com> wrote:
> Cannot repro your problem. The code you posted adds all three URLs to
> the array and prints them in one contiguous line.
>
> C:\tmp>t.plhttp://google.comhttp://amazon.comhttp://ebay.com
This is a mystery. I've run the script on both a Windows and Linux
machine with the same results. Besides, your output should also
include Yahoo, which it doesn't.
I was able to do what I wanted with the following hack. I'm not real
happy about it, but it works. Still, I'd rather know how to do it with
a RE.
CC.
---------hack---------------
while (<DATA>)
{
my @line =3D split /<a/;
foreach my $url (@line)
{
if (/<a.*href=3D"([^"]+)/) { push @urls, $1; }
}
}
------------------------------
Date: Fri, 5 Feb 2010 16:58:40 +0000 (UTC)
From: Willem <willem@stack.nl>
Subject: Re: capturing multiple patterns per line
Message-Id: <slrnhmoji0.d5a.willem@turtle.stack.nl>
ccc31807 wrote:
) This is a newbie question, I admit, but I don't know the answer.
)
) Suppose I am parsing a file line by line, and I want to push to an
) array all substrings on that line that match a pattern. For example,
) consider the listing below. @urls SHOULD contain this: @urls = (http://
) google.com, http://yahoo.com, http://amazon.com, http://ebay.com)
) Instead, it contains only the last value. Using the g modifier doesn't
) help.
)
) I know why @urls contains only the last value, but I don't know how to
) get all the values.
I think you don't actually know why it only contains the last value,
because there are two separate issues with your code.
) Thanks, CC.
)
) -------listing---------------
) use strict;
) use warnings;
)
) my @urls;
) while (<DATA>)
) {
) if (/<a.*href="([^"]+)/) { push @urls, $1; }
) }
First of all, the .* in there will match everything, so in this case it
will match everything from the first <a to the last href="..."
Second, with the /g modifier, the results will not all be put in $1
And third, obviously, this is a lot easier in perl if you realise that it
can do a lot of set processing:
while (<DATA>)
{
push @urls, /<a.*?href="(.*?)"/gi;
}
Or even:
@urls = map { /<a.*?href="(.*?)"/gi } <DATA>
Although that is a lot more memory hungry.
SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something..
No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT
------------------------------
Date: Fri, 5 Feb 2010 09:12:54 -0800 (PST)
From: ccc31807 <cartercc@gmail.com>
Subject: Re: capturing multiple patterns per line
Message-Id: <c963b056-feaf-4457-ac28-c99ca4bbf539@k41g2000yqm.googlegroups.com>
On Feb 5, 11:58=A0am, Willem <wil...@stack.nl> wrote:
> =A0 while (<DATA>)
> =A0 {
> =A0 =A0 push @urls, /<a.*?href=3D"(.*?)"/gi;
> =A0 }
Yes, yes, yes, you are entirely right. I thought that the non-greedy
modifier might do the trick, but (1) I didn't realize that the greedy
version would skip all the way to the last one to the detriment of my
search, and (2) I didn't carefully think through exactly where I
should use the non-greedy modifier.
Thanks, CC.
------------------------------
Date: Fri, 05 Feb 2010 11:22:00 -0600
From: Tad McClellan <tadmc@seesig.invalid>
Subject: Re: capturing multiple patterns per line
Message-Id: <slrnhmokn2.s9v.tadmc@tadbox.sbcglobal.net>
ccc31807 <cartercc@gmail.com> wrote:
> consider the listing below. @urls SHOULD contain this: @urls = (http://
> google.com, http://yahoo.com, http://amazon.com, http://ebay.com)
> Instead, it contains only the last value. Using the g modifier doesn't
> help.
>
> I know why @urls contains only the last value,
I don't think that you do...
> but I don't know how to
> get all the values.
... else that would be pretty easy to fix.
> if (/<a.*href="([^"]+)/) { push @urls, $1; }
if{} is not a loop, so it will execute zero or one time,
so you can push at most one value.
You have a greedy match, so you match the "<a" from the google.com
anchor, the ".*" matches a bazillion characters, and the capture
group captures the *last* one that matches.
><html>\n
><body>\n
><h1>My Favorite Sites</h1>\n
><p>\n
We don't need any of that, as there are no matches there.
Your data really has backslash characters in it?
> My favorite sites are <a href="http://google.com">Google</a>, <a
> href="http://yahoo.com">Yahoo</a>, <a href="http://amazon.com">Amazon</
> a>, and <a href="http://ebay.com">Ebay</a>.\n
If your problem is related to having a long line of data, then you
should ensure that your posting includes a long line of data.
Your "news reader" "helpfully" broke your data by word-wrapping it.
You could have easily avoided that problem by loading $_ yourself.
-----------------
#!/usr/bin/perl
use warnings;
use strict;
$_ = 'My favorite sites are <a href="http://google.com">Google</a>, '
. '<a href="http://yahoo.com">Yahoo</a>, '
. '<a href="http://amazon.com">'
. 'Amazon</ a>, and <a href="http://ebay.com">Ebay</a>.';
my @urls;
while (/<a.*?href="([^"]+)/g) { push @urls, $1; } # m//g in scalar context
print "@urls";
-----------------
However, if it was up to me, I wouldn't do it that way at all.
I'd use m//g in list context and replace the while() with one of:
push @urls, /<a href="([^"]+)/g;
push @urls, /<a[^>]*href="([^"]+)/g;
push @urls, /<a.*?href="([^"]+)/g;
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/"
------------------------------
Date: Fri, 05 Feb 2010 09:22:44 -0800
From: "John W. Krahn" <someone@example.com>
Subject: Re: capturing multiple patterns per line
Message-Id: <FtYan.69148$RS6.45930@newsfe15.iad>
ccc31807 wrote:
> On Feb 5, 11:30 am, Jürgen Exner <jurge...@hotmail.com> wrote:
>> Cannot repro your problem. The code you posted adds all three URLs to
>> the array and prints them in one contiguous line.
>>
>> C:\tmp>t.plhttp://google.comhttp://amazon.comhttp://ebay.com
>
> This is a mystery. I've run the script on both a Windows and Linux
> machine with the same results. Besides, your output should also
> include Yahoo, which it doesn't.
>
> I was able to do what I wanted with the following hack. I'm not real
> happy about it, but it works. Still, I'd rather know how to do it with
> a RE.
>
> ---------hack---------------
> while (<DATA>)
> {
> my @line = split /<a/;
> foreach my $url (@line)
> {
> if (/<a.*href="([^"]+)/) { push @urls, $1; }
That is short for:
if ($_ =~ /<a.*href="([^"]+)/)
So you are not using the results from split() at all and the foreach
loop is superfluous. But if you changed that to:
if ($url =~ /<a.*href="([^"]+)/)
Then it wouldn't work because "split /<a/" removes the string '<a' from
all input and the regular expression requires a match with '<a'.
> }
> }
John
--
The programmer is fighting against the two most
destructive forces in the universe: entropy and
human stupidity. -- Damian Conway
------------------------------
Date: Fri, 05 Feb 2010 09:32:04 -0800
From: Jürgen Exner <jurgenex@hotmail.com>
Subject: Re: capturing multiple patterns per line
Message-Id: <o5lom5tgbkg61moqqq8a17hqfjoaft842a@4ax.com>
ccc31807 <cartercc@gmail.com> wrote:
>On Feb 5, 11:30 am, Jürgen Exner <jurge...@hotmail.com> wrote:
>> Cannot repro your problem. The code you posted adds all three URLs to
>> the array and prints them in one contiguous line.
>>
>> C:\tmp>t.plhttp://google.comhttp://amazon.comhttp://ebay.com
>
>This is a mystery. I've run the script on both a Windows and Linux
>machine with the same results. Besides, your output should also
>include Yahoo, which it doesn't.
After reading the other responses I realize that I was looking at the
wrong problem. You wrote "Instead, it contains only the last value. "
Running your code I saw three distinct values. Three is more than "only
the last", so obviously your claim was wrong.
You never mentioned that you were talking about the RE not
extracting/capturing all the elements from a _SINGLE(!!!)_ line.
Thank you very much for throwing red herring around.
jue
------------------------------
Date: Fri, 05 Feb 2010 18:50:17 +0000
From: RedGrittyBrick <RedGrittyBrick@spamweary.invalid>
Subject: Re: capturing multiple patterns per line
Message-Id: <4b6c686b$0$2486$db0fefd9@news.zen.co.uk>
On 05/02/2010 16:56, ccc31807 wrote:
> On Feb 5, 11:30 am, Jürgen Exner<jurge...@hotmail.com> wrote:
>> Cannot repro your problem. The code you posted adds all three URLs to
>> the array and prints them in one contiguous line.
>>
>> C:\tmp>t.plhttp://google.comhttp://amazon.comhttp://ebay.com
>
> This is a mystery. I've run the script on both a Windows and Linux
> machine with the same results. Besides, your output should also
> include Yahoo, which it doesn't.
Thats because your DATA lines have been reformatted and split onto
several lines!
>
> I was able to do what I wanted with the following hack. I'm not real
> happy about it, but it works. Still, I'd rather know how to do it with
> a RE.
Not every job should be done with an RE
>
> ---------hack---------------
> while (<DATA>)
> {
> my @line = split /<a/;
> foreach my $url (@line)
> {
> if (/<a.*href="([^"]+)/) { push @urls, $1; }
> }
> }
-------------8<-------------
#!/usr/bin/perl
use strict;
use warnings;
my @urls;
while (<DATA>)
{
push @urls, /<a href="([^"]+)/g;
}
print join(',',@urls), "\n";
__DATA__
xxx
x <a href="g">G</a><a href="y">Y</a> x
x <a href="a">A</a><a href="e">E</a> x
xxx
-------------8<-------------
g,y,a,e
------------------------------
Date: Fri, 05 Feb 2010 15:51:14 GMT
From: Peter Scott <Peter@PSDT.com>
Subject: Re: function within qq{}
Message-Id: <S7Xan.22014$aU4.14841@newsfe13.iad>
On Tue, 02 Feb 2010 11:41:14 -0500, Uri Guttman wrote:
>>>>>> "c" == cate <catebekensail@yahoo.com> writes:
>
> c> On Feb 2, 10:18Â am, "John W. Krahn" <some...@example.com> wrote:
> >> cate wrote:
> >> > I know you can do this, I just can't find it. How do you call a
> >> > sub within a qq{} construct
> >>
> >> > qq{The common term for H2O is chem("H2O").}
> >>
> >> perldoc -q "How do I expand function calls in a string"
> >>
> c> @{[mysub(1,2,3)]}
> c> good grief. Thanks
>
> and that is considered a poor construct. i never use it (or its scalar
> cousin) nor do i recommend it. when i review code, i downgrade when i
> see that used. it is simpler and better to just assign to a variable
> before the string and then interpolate it. also it will likely be faster
> as you don't need the reference/dereference. also it will only call your
> code in a list context (even the scalar form!) which may be a problem.
> assigning to your own variable allows you to control the context as
> well.
There is always MJD's Evaluation module (looks like Jenda's expanded on
it some); elegant in execution, a bit heavyweight in the setup, but worth
knowing:
use Evaluation E => 'eval';
qq[The common term for H2O is $E{ chem("H2O") }.]
--
Peter Scott
http://www.perlmedic.com/
http://www.perldebugged.com/
http://www.informit.com/store/product.aspx?isbn=0137001274
------------------------------
Date: Fri, 05 Feb 2010 02:13:34 -0600
From: tadmc@seesig.invalid
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
Message-Id: <kbGdndOj15SzTvbWnZ2dnUVZ_jadnZ2d@giganews.com>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
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If You Like
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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.liamg\100cm.j.dat/"
------------------------------
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:
To submit articles to comp.lang.perl.announce, send your article to
clpa@perl.com.
Back issues are available via anonymous ftp from
ftp://cil-www.oce.orst.edu/pub/perl/old-digests.
#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 V11 Issue 2804
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