[22788] in Perl-Users-Digest
Perl-Users Digest, Issue: 5009 Volume: 10
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue May 20 06:05:43 2003
Date: Tue, 20 May 2003 03:05:10 -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, 20 May 2003 Volume: 10 Number: 5009
Today's topics:
can fork() be an alternative to while (1)? <ah@siol.net>
Re: can fork() be an alternative to while (1)? <john.thetenant-s@moving-picture.com>
Re: Code reference from a subclass (Anno Siegel)
Re: Code reference from a subclass <juanf@lsi.upc.es>
Re: How do I pop this? (Helgi Briem)
Re: How many groups have a regex? <juanf@lsi.upc.es>
Re: How many groups have a regex? (Anno Siegel)
Re: Inserting a record into a table using a value from <bigj@kamelfreund.de>
Re: Inserting a record into a table using a value from <REMOVEsdnCAPS@comcast.net>
Re: making scalar variables from array elements, put in <nobull@mail.com>
Re: Newbie question. Lookup multiple DBI connections <simon.oliver@nospam.umist.ac.uk>
Re: PHP or Perl ? <news-dfn@chaz6.com>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@augustmail.com
Searching and replacing strings in a file (Vinod. K)
Re: Searching and replacing strings in a file <allanon@hotmail.com>
Re: Sending email with perl. <REMOVEsdnCAPS@comcast.net>
Re: Tough question for the guru's; Grep Once, Awk Twice <tassilo.parseval@rwth-aachen.de>
Uppercase question <jon@rogers.tv>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Tue, 20 May 2003 07:48:14 GMT
From: Andrej Hocevar <ah@siol.net>
Subject: can fork() be an alternative to while (1)?
Message-Id: <slrnbcjni6.35c.ah@sonet.utopija.linux>
Hello,
I've never forked anyhing until now, but this time I may have to do it.
I have a curses program that does things for different key-presses,
all of which is inside a while (1) {...} loop. (Of course,) this
takes over the cpu.
Is it possible to do such things with fork? What is the basic idea
behind that? Or is there maybe another trick to wait until a key
really is pressed and then execute the loop?
Thanks,
andrej
--
echo ${girl_name} > /etc/dumpdates
------------------------------
Date: Tue, 20 May 2003 09:36:16 +0100
From: John Strauss <john.thetenant-s@moving-picture.com>
Subject: Re: can fork() be an alternative to while (1)?
Message-Id: <20030520093616.084f7b57.john.thetenant-s@moving-picture.com>
On Tue, 20 May 2003 07:48:14 GMT
Andrej Hocevar <ah@siol.net> wrote:
>
> Hello,
> I've never forked anyhing until now, but this time I may have to do it.
> I have a curses program that does things for different key-presses,
> all of which is inside a while (1) {...} loop. (Of course,) this
> takes over the cpu.
> Is it possible to do such things with fork? What is the basic idea
> behind that? Or is there maybe another trick to wait until a key
> really is pressed and then execute the loop?
>
> Thanks,
>
> andrej
>
> --
> echo ${girl_name} > /etc/dumpdates
I wouldn't use fork(), but then I don't use curses.
Term::ReadKey from CPAN sounds like the ticket, but you may get
a better idea from one of these:
perldoc -q keyboard
perldoc -f select
If you don't care about being particularly efficient, you could
simply stick a "sleep (1)" in your "while (1)" loop to ease the
cpu burden. or you can effect a finer grained sleep with select,
see the above perldocs.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drop the .thetenant to get me via mail
------------------------------
Date: 20 May 2003 09:40:21 GMT
From: anno4000@lublin.zrz.tu-berlin.de (Anno Siegel)
Subject: Re: Code reference from a subclass
Message-Id: <bact65$jsd$2@mamenchi.zrz.TU-Berlin.DE>
Juan Francisco Fernandez Carrasco <juanf@lsi.upc.es> wrote in comp.lang.perl.misc:
> Hi all!
>
> My problem is this:
>
> I have two classes which are like this: A is B's superclass.
> I also have a method "newAddr" in A which gets the code reference from
> the method "new".
> I thought this scheme would give me the code reference of B's "new" if
> I would call "newAddr"
> from a B instance, but this is not what happens. It gives me the code
> reference of A's "new" instead.
So you want a coderef to B's new() method, no matter where B inherits
it from? "my $meth = B->can( 'new')" gives you that.
Anno
------------------------------
Date: Tue, 20 May 2003 11:20:13 +0200
From: Juan Francisco Fernandez Carrasco <juanf@lsi.upc.es>
Subject: Re: Code reference from a subclass
Message-Id: <3EC9F34D.2F5FFD06@lsi.upc.es>
Jay Tilton wrote:
> Juan Francisco Fernandez Carrasco <juanf@lsi.upc.es> wrote:
>
> : I have two classes which are like this: A is B's superclass. I also
> : have a method "newAddr" in A which gets the code reference from the
> : method "new". I thought this scheme would give me the code reference
> : of B's "new" if I would call "newAddr" from a B instance, but this is
> : not what happens. It gives me the code reference of A's "new" instead.
> :
> : The trivial solution, which is to put "newAddr" in class B is not
> : possible.
>
> It's not just the trivial solution, it's the correct solution.
> The method's code reference is essentially class data. You are trying
> to obtain that class data without using the class implementation.
>
> : Could anybody help me with this?
> : Why I get the to te code reference of the superclass (A) instead of
> : that of the subclass (B)?
>
> The newAddr method lives in package A. Calling it from package B does
> not magically put its code (and any symbols used in that code, like
> &new) into package B. Inheritance does not mean symbols are exported.
>
> : What is the way to access the right code reference withou moving
> : "newAddr" from A?
>
> Symbolically.
>
> sub newaddr{
> my $self = shift;
> my $res = \&{ref($self) . "::new"};
> return $res;
> }
>
Hi Jay!
Thanks, with some modifications your code arranges my problem. :-)
sub newAddr(){
my $self=shift @_;
my $res = \&{$self."::new"};
return $res;
}#end of newAddr
The rationale of the change is that newAddr is a class method not a
instance method,
so it receives its class name when called.
Below I try to answer your questions about this code. I hope to be clear
but I apologize because it is hard to me explain some difficult concepts in
English
> I wonder why that doesn't violate "use strict 'refs';".
> I'd bet it exploits the mechanism perl itself uses to symbolically
> resolve method calls into the appropriate package.
>
No idea, maybe the reason is that I first make necessary "use"
of any class that will be called. But I am not sure about this point.
>
> When newaddr is called by an object from a subclass that has no new()
> method, what would you expect to happen?
>
This can not happen. Class A is not intended for distribution but only
for being used inside the application I am working on. Moreover it is
documented
and respected that no subclass can lack of "new" method. :-)
>
> What could you use the constructor's coderef for, anyway?
> It seems an odd thing to want, and would be of limited utility unless
> you already know the package name.
Well, there is more code which in run time reads a directory and emulates
"use" on the classes there stored. Once the "use"'s are done it stores
every "new" reference (got using "newAddr") into a data structure
that will be accessed everytime a new object of this classes is needed.
Overall, the purpose of this is to have an application that can be extended
by only copying new classes to a directory.
thanks again,
Juan Fco Fernandez Carrasco
------------------------------
Date: Tue, 20 May 2003 08:31:01 GMT
From: helgi@decode.is (Helgi Briem)
Subject: Re: How do I pop this?
Message-Id: <3ec9e7b5.3433249011@news.cis.dfn.de>
On Mon, 19 May 2003 10:53:23 -0500, Mark <mark@nospam.com>
wrote:
>tadmc@augustmail.com (Tad McClellan) wrote in
>news:slrnbchk9g.21q.tadmc@magna.augustmail.com:
>
>> http://web.presby.edu/~nnqadmin/nnq/nquote.html
>
>I don't think stopping "top-posting" is a worthwhile endeavour -- I'd
>analogize it to correcting other people's spelling mistakes. In reality, a
>good order in which to read a chain of messages you are (even only
>somewhat) familiar with is in reverse chronological order. The most recent
>stuff is probably the most relevant. At bottom, it comes down to style and
>bureaucratizing style is (at least) undemocratic and (at worst) autocratic.
>
So long then.
*Plonk*
--
Regards, Helgi Briem
helgi DOT briem AT decode DOT is
------------------------------
Date: Tue, 20 May 2003 10:34:39 +0200
From: Juan Francisco Fernandez Carrasco <juanf@lsi.upc.es>
Subject: Re: How many groups have a regex?
Message-Id: <3EC9E89F.ABE050EB@lsi.upc.es>
i5513 wrote:
> Hi again, I need a copy of $1..$last after a $var =~ /$er/ is done.
>
> Is there any var that says how many groups are there at last expression evaluate?
>
> For example, I'd like:
>
> $var =~ /$er/;
> # $n_groups = n_match_parents ($er)
> map { $groups{$_} = ${$_}} 0 .. $n_groups;
>
> How I can get $n_groups?
> Thank you very much.
Hi!
Parse $er looking for the amount of parentheses "(" ")" it
contains.
this code could do the work:
my $n_higher_group;
my $erAux=$er;
while($erAux=~/\(/){
$n_higher_group++;
$erAux=$';
}
once you have this processed $n_higher_group will
be a upper bound for the amount of $x which have
a matched value inside.
Keep in mind that $er must be a correct expression (i.e. must have balanced and
correctly nested parentheses)
for this code to work properly.
I hope this help you, enjoy PERL
Juan Fco Fernandez
------------------------------
Date: 20 May 2003 09:17:24 GMT
From: anno4000@lublin.zrz.tu-berlin.de (Anno Siegel)
Subject: Re: How many groups have a regex?
Message-Id: <bacrr4$jsd$1@mamenchi.zrz.TU-Berlin.DE>
Juan Francisco Fernandez Carrasco <juanf@lsi.upc.es> wrote in comp.lang.perl.misc:
> i5513 wrote:
>
> > Hi again, I need a copy of $1..$last after a $var =~ /$er/ is done.
> >
> > Is there any var that says how many groups are there at last
> expression evaluate?
> >
> > For example, I'd like:
> >
> > $var =~ /$er/;
> > # $n_groups = n_match_parents ($er)
> > map { $groups{$_} = ${$_}} 0 .. $n_groups;
> >
> > How I can get $n_groups?
> > Thank you very much.
>
> Hi!
>
> Parse $er looking for the amount of parentheses "(" ")" it
> contains.
> this code could do the work:
>
> my $n_higher_group;
> my $erAux=$er;
> while($erAux=~/\(/){
>
> $n_higher_group++;
> $erAux=$';
>
> }
>
> once you have this processed $n_higher_group will
> be a upper bound for the amount of $x which have
> a matched value inside.
This won't work as intended.
There are lots of ways parentheses can occur in a regex. Only some
of them capture matches. Short of actually parsing the regex, it
will be very hard to find which do and which don't.
> Keep in mind that $er must be a correct expression (i.e. must have balanced and
> correctly nested parentheses)
> for this code to work properly.
>
> I hope this help you, enjoy PERL
^^^^
"Perl"
Anno
------------------------------
Date: Tue, 20 May 2003 07:07:06 +0200
From: "Janek Schleicher" <bigj@kamelfreund.de>
Subject: Re: Inserting a record into a table using a value from a sequence
Message-Id: <pan.2003.05.20.05.07.05.574665@kamelfreund.de>
Uma Mahesh wrote at Mon, 19 May 2003 22:41:28 -0700:
> I want to insert a record into a database table with a value from a sequence.
>
> When ever I try to do that I get a invalid number.
>
> Any help or pointers are appreciated.
Any code is appreciated.
I'm sorry, but without examples and more details, I'm afraid, we can't
help you.
What kind of database (MySQL, Oracle, DB2, PostgreSQL)?
What exactly do you mean with "sequence"?
What with "record"?
What is the exact SQL error message?
What's the Perl code raising the problem?
What's the definition of your table (columns)?
Greetings,
Janek
------------------------------
Date: Tue, 20 May 2003 04:50:55 -0500
From: "Eric J. Roode" <REMOVEsdnCAPS@comcast.net>
Subject: Re: Inserting a record into a table using a value from a sequence
Message-Id: <Xns93813B63841F4sdn.comcast@216.166.71.239>
-----BEGIN xxx SIGNED MESSAGE-----
Hash: SHA1
uma@bluemartini.com (Uma Mahesh) wrote in
news:e20faad0.0305192141.163f0b21@posting.google.com:
> Hi there,
>
> I want to insert a record into a database table with a value from a
> sequence.
>
> When ever I try to do that I get a invalid number.
>
> Any help or pointers are appreciated.
>
Perhaps the error is on line 36 of your script.
HTH.
- --
Eric
print scalar reverse sort qw p ekca lre reh
ts uJ p, $/.r, map $_.$", qw e p h tona e;
-----BEGIN xxx SIGNATURE-----
Version: PGPfreeware 7.0.3 for non-commercial use <http://www.pgp.com>
iQA/AwUBPsn6VmPeouIeTNHoEQKGzQCfWClEdbMUaaZzGx9OcfxCXCNr5RsAoJ1i
y58wcZVVGxrsDsOUB7/UMgBx
=muXP
-----END PGP SIGNATURE-----
------------------------------
Date: 20 May 2003 09:01:19 +0100
From: Brian McCauley <nobull@mail.com>
Subject: Re: making scalar variables from array elements, put into table
Message-Id: <u9fznadp2o.fsf@wcl-l.bham.ac.uk>
lepore@brandeis.edu (bryan) writes:
> Brian McCauley <nobull@mail.com> wrote in message writes:
> > > so i guess the simple question is, can i make scalar variables from
> > > array elements?
> >
> > Array elements are scalar variables.
> > I suspect you are looking for symbolic references.
> > Stop doing so - just use a suitably shaped array.
>
> should i also quit trying to make the loop create new variables?
You should quit trying to make a loop create (or otherwise manipulate)
many descrete, similarly named, scalar variables.
If you have something that is naturally a multi-dimentional array then
store it as such.
------------------------------
Date: Tue, 20 May 2003 10:12:57 +0100
From: Simon Oliver <simon.oliver@nospam.umist.ac.uk>
Subject: Re: Newbie question. Lookup multiple DBI connections
Message-Id: <3EC9F199.7020604@nospam.umist.ac.uk>
ThePotPlants wrote:
> 1: What s the best way to refer to an external file that is only used for
> 'lookups'.
A tied hash is the most obvious, perhaps with SDBM_File? The key would be
'sap', 'fin', etc. You could serialize the associated data using
join/split, use one of the data serializing modules such as Data::Dumper,
FreezeThaw, or Storable, or use MLDBM to do all this for you :-)
Another interesting possibility is to use DBI with DBD::AnyData.
It will read in most common configuration file formats (why not use CSV or
XML?) and you then work with the data using SQL commands:
#!/usr/bin/perl -w
use strict;
use DBI;
my $dbh = DBI->connect('dbi:AnyData(RaiseError=>1):');
$dbh->func( 'conns', 'CSV', [<DATA>], {col_names=>'id,conn,uid,pwd'},
'ad_import');
my $sql = q{SELECT * FROM conns WHERE id = 'sap'};
my $sth = $dbh->prepare($sql);
$sth->execute;
my $row = $sth->fetch
or die "No such connection id!\n";
print join(',',@$row), "\n";
$dbh->disconnect;
__DATA__
sap,"DBI:oracle:databas1","usernam1","pwdx"
fin,"DBI:sybase:database","usernam2","pwdx"
hr,"DBI:oracle:database3","usernam5","pwdx"
------------------------------
Date: Tue, 20 May 2003 08:11:27 +0100
From: "Chaz" <news-dfn@chaz6.com>
Subject: Re: PHP or Perl ?
Message-Id: <backg8$r7l9u$1@ID-117927.news.dfncis.de>
"Hans Wolters" <nomailwanted@e35203.upc-e.chello.nl> wrote in message
news:HtJxa.1783563$sj7.76865652@Flipper...
> brucie wrote:
> > In post <3ec6c663$0$49117$e4fe514c@news.xs4all.nl>
> > Dieter D'Hoker babbled:
> >
> >
> >>How would you advice someone who wants to start learning a programmign
> >>language for developping websites ?
> >>learning PHP or Perl ?
> >
> >
> > PHP is yummy and easy.
> >
> > perl is soooo 1990s
>
> Perl might be a little older but is sure does the job. Use whatever you
> need.
Age brings maturity :o)
Regards,
Chris
------------------------------
Date: Tue, 20 May 2003 02:24:24 -0500
From: tadmc@augustmail.com
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.4 $)
Message-Id: <eYycnbrBYsy1RVSjXTWcpg@august.net>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($Revision: 1.4 $)
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.
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
"Jeopardy" (because the answer comes before the question), or
"TOFU".
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: 20 May 2003 02:05:19 -0700
From: pkvinu@indiatimes.com (Vinod. K)
Subject: Searching and replacing strings in a file
Message-Id: <bde4ceed.0305200105.592b2e9f@posting.google.com>
Hello All,
I have 2 questions ( Here my working environmet is unix):
1.) In unix environment, I got a text file in which I need to search
and replace a string/s. Is there any specific module or command ????
2.) I want to create some text file which I can able to open in
windows word application. I mean - read a input file and create output
file which should be a word document. is this possible to create the
word document??? and other question is - is it possible to insert a
log into this document or any other text file ???
Please help me.
Please forgive, if in any case, already such queries are asked.
I have searched in this group and didn't get anything related to my
queries.
Thanks and Regards,
- vinod.
------------------------------
Date: Tue, 20 May 2003 10:38:05 +0100
From: "Allanon" <allanon@hotmail.com>
Subject: Re: Searching and replacing strings in a file
Message-Id: <bact1t$12je@newton.cc.rl.ac.uk>
"Vinod. K" <pkvinu@indiatimes.com> wrote in message
news:bde4ceed.0305200105.592b2e9f@posting.google.com...
> Hello All,
>
> I have 2 questions ( Here my working environmet is unix):
>
> 1.) In unix environment, I got a text file in which I need to search
> and replace a string/s. Is there any specific module or command ????
Not 100% sure about the file path syntax for unix, but u could use sth like:
# variables
$str_to_replace = "blah";
$replace_with = "blah blah";
# get file into array
open(FILE,"/usr/data/myfile");
@lines = <FILE>;
close(FILE);
# perform string replace
foreach(@lines){
$_ =~ s/$str_to_replace/$replace_with/g; # add i after g to make
case-insensitive
}
# write back to file
open(FILE,">/usr/data/myfile");
foreach(@lines){
print FILE $_;
}
close(FILE);
> 2.) I want to create some text file which I can able to open in
> windows word application. I mean - read a input file and create output
> file which should be a word document. is this possible to create the
> word document??? and other question is - is it possible to insert a
> log into this document or any other text file ???
A Microsoft Word file is normally a binary file due to all the formatting
and ibjects you can insert. However, you can create a normal text file with
the extension ".doc" and it will open in Word. When it's opened it'll
default to something like Courier font.
Allanon
------------------------------
Date: Tue, 20 May 2003 04:48:19 -0500
From: "Eric J. Roode" <REMOVEsdnCAPS@comcast.net>
Subject: Re: Sending email with perl.
Message-Id: <Xns93813AF26470Csdn.comcast@216.166.71.239>
-----BEGIN xxx SIGNED MESSAGE-----
Hash: SHA1
"Chip" <chip@afcoms.NOSPAM.com> wrote in news:4Bgya.1313$7S2.1028589
@news1.news.adelphia.net:
> I am trying to have a simple script email me when a
> server is not responding to ping.
>
> I can run mailx from the command line and it works
> fine but the script never sends mail.
> system("mailx administrator@host.com", "Alert", "Server $_ is
> down", ".", " ");
So read the documentation on system(). Additional arguments to system()
are not passed on stdin, if that's what you're thinking.`
Try using open(), with the | character. open("mailx you@there.com |").
See 'perldoc -f open' for details.
- --
Eric
print scalar reverse sort qw p ekca lre reh
ts uJ p, $/.r, map $_.$", qw e p h tona e;
-----BEGIN xxx SIGNATURE-----
Version: PGPfreeware 7.0.3 for non-commercial use <http://www.pgp.com>
iQA/AwUBPsn5t2PeouIeTNHoEQIeIQCeMIurAyDB/T2fjbCbZdSlBWcWqlsAmQHD
CcT3m8RGvvrPApXOQl6gnHei
=9BVF
-----END PGP SIGNATURE-----
------------------------------
Date: 20 May 2003 08:14:10 GMT
From: "Tassilo v. Parseval" <tassilo.parseval@rwth-aachen.de>
Subject: Re: Tough question for the guru's; Grep Once, Awk Twice (or more)
Message-Id: <baco4i$9oa$1@nets3.rz.RWTH-Aachen.DE>
Also sprach Agrapha:
> "Tassilo v. Parseval" <tassilo.parseval@rwth-aachen.de> wrote in message news:<b8iqr3$g6r$1@nets3.rz.RWTH-Aachen.DE>...
>
>> Same here. Also, you only ever access the fourth and eigth element of
>> the list returned by split. You can make that explicit:
>>
>
> first quick question, if I load my hash array with data, when I print
> it to the screen how do I sort only on the key and not the value?
The term "hash array" is a little sloppy. Either it's a hash or an
array, but never both. From what follows below I assume it's a hash of
hashes. I'll comment on this question later below because you need to be
a little more familiar with references in order to understand.
>> foreach (@badcalls) {
>> my ($users, $code) = (split)[3,7];
>> $error_codes{ $code }++;
>> $error_users{ $users }++;
>> $err_per_usr{ "$users:$code" }++;
>> }
>>
>> For $err_per_usr you could also use a nested data-structure, a hash of
>> hashes probably:
>>
>> $err_per_usr{ $user }->{ $code }++;
>>
>
> these hashes are hard for me to understand how to manipulate.
In that case you should perhaps start with 'perldoc perlreftut' and
maybe afterwords 'perldoc perldsc'. The latter explicitely deals with
more complex data-structures.
>> > #####
>> > # this one is broke I am supposed to get the 3 columns but
>> > # I dont know how to do that yet
>> > ###
>> > print "\nNumber / Error / Totals\n";
>> > print "-----------------------\n";
>> > foreach my $key (keys %err_per_usr) {
>> > print "$key\t\/\t$err_per_usr{$key}\n";
>> > }
>>
>> This is because %err_per_usr wasn't properly created. If it is a
>> two-dimensional hash, it could look like:
>>
>> while (my ($user, $val) = each %err_per_usr) {
>> # $val is now a hash-ref
>> my %errors = %$val;
>> # proceed
>> }
>>
>
> I have tried a few different renditions but my hashes are not working.
> I think a hash of hashes is what I am looking for but I can't work out
> the correct syntax.
It all starts with filling the hash. First of all, it's useful to know
how your structure is eventually supposed to look like:
> Each line of my file has a phone number and an error-code. (column 4
> and 8) what I would like to do is count how many times each phone
> number returns each error code.
A reasonable structure for that would read as follows:
my %errors = (
2005551313 => {
101 => 10,
4 => 13,
},
2005551313 => {
63 => 21,
44 => 21,
},
...
);
The first thing to not is the difference between round parens '()' and
curly onces '{}'. The latter (besides denoting a block of code) also act
as constructors for a reference to an anonymous hash. The referenced
hash has no name, hence it's an anonymous. That way you could disguise
an ordinary hash as a scalar, too:
my %hash = ( key1 => 'value1',
key2 => 'value2', );
# similar but using a reference
my $hash_ref = { key1 => 'value1',
key2 => 'value2', };
Both of the above describe the same data-structure but the second
version uses a reference to an anon hash. That means, the handling of
these two variables differes as well:
print $hash{ key1 };
# as opposed to
my %tmp_hash = %{ $hash_ref };
$tmp_hash{ key1 };
As you see, a hash-reference can easily be turned into the actual hash
that the reference pointed to in the first place. Perl has a quite
consistent way of turning a reference back into what it originally was:
@array = @{ $ARRAY_REF };
^ ^
%hash = %{ $HASH_REF };
^ ^
$scalar = ${ $SCALAR_REF };
^ ^
The system behind that should be obvious from the above (mark the
correspondance between the marked characters in each line).
Now you may remark that it's cumbersome to first turn a reference into a
different object before accessing its elements. So it is and that's why
there's a shortcut (two actually):
my $hash_ref = { key1 => 'value1',
key2 => 'value2', };
# first one
print ${$hash_ref}{ key1 };
# and
print $hash_ref->{ key1 };
The first shortcut looks like a contradiction at first sight because it
uses '${ $hash_ref }' instead of '%{ $hash_ref }'. But it's not. Access
to a hash-element happens thusly:
$hash{ key };
but never with
%hash{ key };
If you read "Rule 1" from perlreftut.pod you'll learn that any place
where the name of a hash is expected you can put '{$hash_ref}' instead.
So now it's a simple task of text-substitution:
$name_of_hash{ key };
`----------'
|
replace with
|
,-----------------,
${$name_of_hash_ref}{ key };
The second shortcut ('$hash_ref->{ key1 }') is more straightforward.
$hash_ref is a reference so it 'points to' something, therefore you
could read it as
Take the thing that $hash_ref points to ('$hash_ref->') and give me
the element "key" from it ('{ key }').
If you have an array-reference you use different parens but otherwise it
is very similar:
$array_ref->[ 1 ];
The parens you need to use are the ones you use to subscript particular
elements from the plain hash or array:
$hash{ key };
^ ^
$hash_ref->{ key };
^ ^
$array[ 1 ];
^ ^
$array_ref->[ 1 ];
^ ^
Turning back to reference constructors, you use square brackets to
construct a reference to an anonymous array:
my $array_ref = [ 1, 2, 3 ];
# but
my $hash_ref = { key => 'value' };
> The data output should look something
> like:
> number error qty
> 2005551313 - 101,4 - 23
> 2005551313 - 63,44 - 42
> 2005551700 - 60,42 - 10
So the phone-numbers are the primary keys of your hash and the
error-codes the keys of the nested hash. Your original description was:
> Each line of my file has a phone number and an error-code. (column
> 4 and 8) what I would like to do is count how many times each
> phone number returns each error code.
This then translates into:
my %errors;
while (<HANDLE>) {
my ($phone, $err_code) = (split)[3,7];
$errors{ $phone }->{ $err_code }++;
}
$errors{ $phone } is the reference to the hash with the different
error-codes as keys. You want to set a particular value of this
referenced hash and so this results in the above.
Once you have filled your hash, you can dump it. You want to sort on
phone-numbers, therefore:
for my $n (sort { $a <=> $b } keys %errors) {
# $errors{ $n } is now itself a reference to a hash
my %codes = %{ $errors{ $n } };
# compute the total numbers of errors for this phone-number
my $qty;
for ( keys %codes ) {
$qty += $codes{ $_ };
}
# display the stats for a given phone-number $n
print "$n - ", join (",", keys %codes), " - $qty\n";
}
> so my question is, Am I trying to do a hash of hashes?
A hash of hashes looks natural enough for this problem. The advantage of
such compound data-structures is that they can easily be extended and
made arbitrarily complex. A hash of hashes (of hashes of ...) is like a
tree with arbitrary number of children in each node where each
child-path has a name (the key of the respective hash).
Despite the above, read the relevant perldocs. References are too useful
to now be very familiar with them. Perhaps in this order:
perlreftut # the tutorial
perllol # arrays of arrays (List Of Lists actually)
perldsc # Data Structure Cookbook
perlref # everything about references
Tassilo
--
$_=q#",}])!JAPH!qq(tsuJ[{@"tnirp}3..0}_$;//::niam/s~=)]3[))_$-3(rellac(=_$({
pam{rekcahbus})(rekcah{lrePbus})(lreP{rehtonabus})!JAPH!qq(rehtona{tsuJbus#;
$_=reverse,s+(?<=sub).+q#q!'"qq.\t$&."'!#+sexisexiixesixeseg;y~\n~~dddd;eval
------------------------------
Date: Tue, 20 May 2003 12:13:31 +0200
From: Jon Rogers <jon@rogers.tv>
Subject: Uppercase question
Message-Id: <3EC9FFCB.6435D88A@rogers.tv>
Hello
$name="jonathan";
If I want to make the first - and only the first - letter uppercase, is
there an easier way than splitting into array, 'uc' array[0], and then
join again?
/ JR
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
Administrivia:
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------------------------------
End of Perl-Users Digest V10 Issue 5009
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