[31519] in Perl-Users-Digest
Perl-Users Digest, Issue: 2778 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue Jan 19 06:09:42 2010
Date: Tue, 19 Jan 2010 03:09:05 -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 Tue, 19 Jan 2010 Volume: 11 Number: 2778
Today's topics:
Re: a defense of ad hoc software development (Rob Warnock)
Re: embedded Perl process in Apache using mod_perl <sysadmin@example.com>
Re: perl runtime model <RedGrittyBrick@spamweary.invalid>
Re: perl runtime model <hjp-usenet2@hjp.at>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@seesig.invalid
Re: search and replace in Perl <sysadmin@example.com>
Re: Variable set to 0 <uri@StemSystems.com>
Re: Variable set to 0 <sysadmin@example.com>
Re: Variable set to 0 <ben@morrow.me.uk>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Tue, 19 Jan 2010 02:12:45 -0600
From: rpw3@rpw3.org (Rob Warnock)
Subject: Re: a defense of ad hoc software development
Message-Id: <5-SdnUKg1N3g9MjWnZ2dnUVZ_umdnZ2d@speakeasy.net>
Greg Menke <gusenet@comcast.net> wrote:
+---------------
| And whatever your write Shall Conform to several (possibly
| contradictory) coding standards both locally defined and those visited
| upon the world by ISO/CMMI (as mandated by management who doesn't
| actually have to use them). And whatever you do end up coding has to be
| documented according to appendices of the aforementioned standards
| specs, and all changes to it also Shall Conform to the change control
| specs. And when you put your (surviving) code through Validation &
| Verification, the pencil pushers who apply that process have full
| editorial control over your code- from accept to change to reject, and
| are unencumbered by any knowledge, responsibility or accountability for
| the project.
+---------------
Charles Stross <http://www.antipope.org/charlie/blog-static/fiction/faq.html>
does a pretty good job of capturing the insanity of this in his
"Laundry" stories ["The Atrocity Archives", "The Concrete Jungle",
"The Jennifer Morgue", and "The Fuller Memorandum" (due July 2010)].
E.g., exactly how *does* a top-secret intelligence agency deal with
ISO-9002 conformance and outsourced COTS application infrastructure
and audits by the BSA(!) and DRM on essential operational software?!?
;-} ;-}
-Rob
-----
Rob Warnock <rpw3@rpw3.org>
627 26th Avenue <URL:http://rpw3.org/>
San Mateo, CA 94403 (650)572-2607
------------------------------
Date: Mon, 18 Jan 2010 22:33:36 -0800
From: Wanna-Be Sys Admin <sysadmin@example.com>
Subject: Re: embedded Perl process in Apache using mod_perl
Message-Id: <5nc5n.19143$Wl3.12887@newsfe11.iad>
ccc31807 wrote:
> Could someone give a simple and short explanation of what it means to
> say that mod_perl embeds a Perl process in Apache?
>
> I understand that classical CGI passes requests for a script to Perl,
> which fires up a Perl process, runs the script, returns a value, and
> shuts down. I also understand that FastCGI does the same thing except
> that the Perl process doesn't start and stop with each request but
> remains running in the background.
>
> However, I don't understand t mechanism of an embedded Perl process in
> mod_perl, and the question seems so elementary that the documentation
> doesn't address it. Or maybe I just haven't read the right
> documentation.
>
> Thanks, CC.
mod_perl knows to parse the text in the file as a script (look or try
to, depending) without spawning a new process outside of the already
running httpd process. It saves overhead from not spawning an
additional process (other than additionally needed httpd processes
themselves, possibly, but that's about the request, rather than the
script). Be aware that mod_perl needs to run the process as the global
web server user, not the user that it'd run as if you had a CGI
wrapper, such as Apache would normally use, which can be better or
worse depending if you're in a shared or trusted server environment.
Also, the possibility of memory leaks causing issues where a CGI
process is separate and can be controlled individually, along with
other CGI scripts. Depending on the module and framework, a process
can wait for connections without opening a new call/process, etc. to
handle future or multiple requests, therein saving more resources than
just avoiding CGI overhead. I'd rather recommend FastCGI over mod_perl
for reasons of security on a shared user server environment, unless you
each run your own instance of the web service anyway.
--
Not really a wanna-be, but I don't know everything.
------------------------------
Date: Tue, 19 Jan 2010 10:20:09 +0000
From: RedGrittyBrick <RedGrittyBrick@spamweary.invalid>
Subject: Re: perl runtime model
Message-Id: <4b55875a$0$2533$da0feed9@news.zen.co.uk>
Peng Yu wrote:
> What parts make a perl script be slower than an equivalent, say, C
> programe?
What use do you intend to make of the answer?
What motivates your question?
Do you have a Perl script that is slow?
--
RGB
Algorithms Algorithms Algorithms ...
------------------------------
Date: Tue, 19 Jan 2010 11:20:37 +0100
From: "Peter J. Holzer" <hjp-usenet2@hjp.at>
Subject: Re: perl runtime model
Message-Id: <slrnhlb1rs.ucq.hjp-usenet2@hrunkner.hjp.at>
On 2010-01-19 02:19, Jürgen Exner <jurgenex@hotmail.com> wrote:
> Peng Yu <pengyu.ut@gmail.com> wrote:
>>I don't think that you understand what I meant.
>
> To be honest I don't either.
>
>>It is not obvious what makes any interpreted language
>>slower than a compiled one. I want to know exactly what make an
>>interpreted language slower.
>
> That is a question for a compiler construction class.
> In short: all of the analytical work (scanner, parser, context checker)
> as well as some sort of code generation (this varies very widely because
> of the many different styles of interpreters) that a compiler does
> upfront must to be done by the interpreter at runtime and thus adds
> significant overhead to interpreted program execution.
Most interpreters (for example, perl) first compile the source code into
an intermediate form which is then interpreted. So the overhead you
mention (analytical work, code generation) only happens at startup and
is negligible unless your program is invoked very frequently.
There are two differences which are much more important:
* To interpret the "byte code" (which doesn't actually have 1 byte
opcodes, but the name is traditional), the interpreter has to fetch
every instruction from memory, decide what to do with it and call the
appropriate code, which will also manipulate data structures in main
memory. A CPU also contains an interpreter (either hardwired or
written in microcode) that has to fetch each instruction, decide what
to do with it and then do it - but that interpreter mainly needs to
manipulate data structures within the CPU, which is a lot faster, it
can do things in parallel (like fetching the next instruction while
decoding the current one and executing the previous one), etc.
Therefore interpreting native machine code is (sometimes a lot)
faster than interpreting a non-native code.
* Dynamically typed languages like perl need to do a lot of checks at
run time. The C compiler knows that two variables are of type signed
int, and for a division can generate code which does a 32-bit signed
division. At run time, this is fixed and doesn't have to be checked
any more. But the perl compiler only knows that it has two scalars.
So the interpreter needs to check at run time whether those scalars
are undef, signed int, unsigned int, or floating point numbers,
strings or objects and select the approriate code path.
I wrote above that the compilation overhead is negligible for most
scripts, but there is a catch: To keep that overhead negligible the
compiler needs to fast - so it cannot perform extensive analysis and
hence cannot produce very good code (for example, a data flow analysis
might show that some perl variables always only contain integer values
and the compiler could take advantage of that, but for most scripts that
would take more time than it saves - you don't want to do that every
time you run your script).
>>And if perl is slow because it is interpreted,
>
> Perl is not slow. For what it does it's pretty darn fast.
For any given task, a Perl program is slower than the equivalent C
program. Whether that is "slow" or "fast" in any objective sense is IMHO
quite irrelevant to the discussion.
Also, interpreter technology has advanced quite a bit since the
mid-1990s. A newly designed language which does "what perl does" could
be quite a bit faster. Even a clean reimplementation of Perl (the
programming language as documented - not counting stuff like XS,
implementation quirks, etc.) probably could be noticably faster.
>>can a perl script be compiled to a machine executable
>>code
>
> No, because Perl supports self-modifying programs, see "perldoc -f
> eval".
Eval is probably the least of your worries. Including an interpreter (or
compiler) for that purpose is simple. The interconnections between
compiler and interpreter during the compilation phase are probably
harder. Still could be possible but I wonder whether it's worth the
effort - you still have to do all that run-time type checking stuff.
hp
------------------------------
Date: Tue, 19 Jan 2010 02:13:25 -0600
From: tadmc@seesig.invalid
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
Message-Id: <1LadnWjTY-849MjWnZ2dnUVZ_vednZ2d@giganews.com>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
This newsgroup, commonly called clpmisc, is a technical newsgroup
intended to be used for discussion of Perl related issues (except job
postings), whether it be comments or questions.
As you would expect, clpmisc discussions are usually very technical in
nature and there are conventions for conduct in technical newsgroups
going somewhat beyond those in non-technical newsgroups.
The article at:
http://www.catb.org/~esr/faqs/smart-questions.html
describes how to get answers from technical people in general.
This article describes things that you should, and should not, do to
increase your chances of getting an answer to your Perl question. It is
available in POD, HTML and plain text formats at:
http://www.rehabitation.com/clpmisc.shtml
For more information about netiquette in general, see the "Netiquette
Guidelines" at:
http://andrew2.andrew.cmu.edu/rfc/rfc1855.html
A note to newsgroup "regulars":
Do not use these guidelines as a "license to flame" or other
meanness. It is possible that a poster is unaware of things
discussed here. Give them the benefit of the doubt, and just
help them learn how to post, rather than assume that they do
know and are being the "bad kind" of Lazy.
A note about technical terms used here:
In this document, we use words like "must" and "should" as
they're used in technical conversation (such as you will
encounter in this newsgroup). When we say that you *must* do
something, we mean that if you don't do that something, then
it's unlikely that you will benefit much from this group.
We're not bossing you around; we're making the point without
lots of words.
Do *NOT* send email to the maintainer of these guidelines. It will be
discarded unread. The guidelines belong to the newsgroup so all
discussion should appear in the newsgroup. I am just the secretary that
writes down the consensus of the group.
Before posting to comp.lang.perl.misc
Must
This section describes things that you *must* do before posting to
clpmisc, in order to maximize your chances of getting meaningful replies
to your inquiry and to avoid getting flamed for being lazy and trying to
have others do your work.
The perl distribution includes documentation that is copied to your hard
drive when you install perl. Also installed is a program for looking
things up in that (and other) documentation named 'perldoc'.
You should either find out where the docs got installed on your system,
or use perldoc to find them for you. Type "perldoc perldoc" to learn how
to use perldoc itself. Type "perldoc perl" to start reading Perl's
standard documentation.
Check the Perl Frequently Asked Questions (FAQ)
Checking the FAQ before posting is required in Big 8 newsgroups in
general, there is nothing clpmisc-specific about this requirement.
You are expected to do this in nearly all newsgroups.
You can use the "-q" switch with perldoc to do a word search of the
questions in the Perl FAQs.
Check the other standard Perl docs (*.pod)
The perl distribution comes with much more documentation than is
available for most other newsgroups, so in clpmisc you should also
see if you can find an answer in the other (non-FAQ) standard docs
before posting.
It is *not* required, or even expected, that you actually *read* all of
Perl's standard docs, only that you spend a few minutes searching them
before posting.
Try doing a word-search in the standard docs for some words/phrases
taken from your problem statement or from your very carefully worded
"Subject:" header.
Really Really Should
This section describes things that you *really should* do before posting
to clpmisc.
Lurk for a while before posting
This is very important and expected in all newsgroups. Lurking means
to monitor a newsgroup for a period to become familiar with local
customs. Each newsgroup has specific customs and rituals. Knowing
these before you participate will help avoid embarrassing social
situations. Consider yourself to be a foreigner at first!
Search a Usenet archive
There are tens of thousands of Perl programmers. It is very likely
that your question has already been asked (and answered). See if you
can find where it has already been answered.
One such searchable archive is:
http://groups.google.com/advanced_search
If You Like
This section describes things that you *can* do before posting to
clpmisc.
Check Other Resources
You may want to check in books or on web sites to see if you can
find the answer to your question.
But you need to consider the source of such information: there are a
lot of very poor Perl books and web sites, and several good ones
too, of course.
Posting to comp.lang.perl.misc
There can be 200 messages in clpmisc in a single day. Nobody is going to
read every article. They must decide somehow which articles they are
going to read, and which they will skip.
Your post is in competition with 199 other posts. You need to "win"
before a person who can help you will even read your question.
These sections describe how you can help keep your article from being
one of the "skipped" ones.
Is there a better place to ask your question?
Question should be about Perl, not about the application area
It can be difficult to separate out where your problem really is,
but you should make a conscious effort to post to the most
applicable newsgroup. That is, after all, where you are the most
likely to find the people who know how to answer your question.
Being able to "partition" a problem is an essential skill for
effectively troubleshooting programming problems. If you don't get
that right, you end up looking for answers in the wrong places.
It should be understood that you may not know that the root of your
problem is not Perl-related (the two most frequent ones are CGI and
Operating System related), so off-topic postings will happen from
time to time. Be gracious when someone helps you find a better place
to ask your question by pointing you to a more applicable newsgroup.
How to participate (post) in the clpmisc community
Carefully choose the contents of your Subject header
You have 40 precious characters of Subject to win out and be one of
the posts that gets read. Don't waste them. Take care while
composing them, they are the key that opens the door to getting an
answer.
Spend them indicating what aspect of Perl others will find if they
should decide to read your article.
Do not spend them indicating "experience level" (guru, newbie...).
Do not spend them pleading (please read, urgent, help!...).
Do not spend them on non-Subjects (Perl question, one-word
Subject...)
For more information on choosing a Subject see "Choosing Good
Subject Lines":
http://www.cpan.org/authors/id/D/DM/DMR/subjects.post
Part of the beauty of newsgroup dynamics, is that you can contribute
to the community with your very first post! If your choice of
Subject leads a fellow Perler to find the thread you are starting,
then even asking a question helps us all.
Use an effective followup style
When composing a followup, quote only enough text to establish the
context for the comments that you will add. Always indicate who
wrote the quoted material. Never quote an entire article. Never
quote a .signature (unless that is what you are commenting on).
Intersperse your comments *following* each section of quoted text to
which they relate. Unappreciated followup styles are referred to as
"top-posting", "Jeopardy" (because the answer comes before the
question), or "TOFU" (Text Over, Fullquote Under).
Reversing the chronology of the dialog makes it much harder to
understand (some folks won't even read it if written in that style).
For more information on quoting style, see:
http://web.presby.edu/~nnqadmin/nnq/nquote.html
Speak Perl rather than English, when possible
Perl is much more precise than natural language. Saying it in Perl
instead will avoid misunderstanding your question or problem.
Do not say: I have variable with "foo\tbar" in it.
Instead say: I have $var = "foo\tbar", or I have $var = 'foo\tbar',
or I have $var = <DATA> (and show the data line).
Ask perl to help you
You can ask perl itself to help you find common programming mistakes
by doing two things: enable warnings (perldoc warnings) and enable
"strict"ures (perldoc strict).
You should not bother the hundreds/thousands of readers of the
newsgroup without first seeing if a machine can help you find your
problem. It is demeaning to be asked to do the work of a machine. It
will annoy the readers of your article.
You can look up any of the messages that perl might issue to find
out what the message means and how to resolve the potential mistake
(perldoc perldiag). If you would like perl to look them up for you,
you can put "use diagnostics;" near the top of your program.
Do not re-type Perl code
Use copy/paste or your editor's "import" function rather than
attempting to type in your code. If you make a typo you will get
followups about your typos instead of about the question you are
trying to get answered.
Provide enough information
If you do the things in this item, you will have an Extremely Good
chance of getting people to try and help you with your problem!
These features are a really big bonus toward your question winning
out over all of the other posts that you are competing with.
First make a short (less than 20-30 lines) and *complete* program
that illustrates the problem you are having. People should be able
to run your program by copy/pasting the code from your article. (You
will find that doing this step very often reveals your problem
directly. Leading to an answer much more quickly and reliably than
posting to Usenet.)
Describe *precisely* the input to your program. Also provide example
input data for your program. If you need to show file input, use the
__DATA__ token (perldata.pod) to provide the file contents inside of
your Perl program.
Show the output (including the verbatim text of any messages) of
your program.
Describe how you want the output to be different from what you are
getting.
If you have no idea at all of how to code up your situation, be sure
to at least describe the 2 things that you *do* know: input and
desired output.
Do not provide too much information
Do not just post your entire program for debugging. Most especially
do not post someone *else's* entire program.
Do not post binaries, HTML, or MIME
clpmisc is a text only newsgroup. If you have images or binaries
that explain your question, put them in a publically accessible
place (like a Web server) and provide a pointer to that location. If
you include code, cut and paste it directly in the message body.
Don't attach anything to the message. Don't post vcards or HTML.
Many people (and even some Usenet servers) will automatically filter
out such messages. Many people will not be able to easily read your
post. Plain text is something everyone can read.
Social faux pas to avoid
The first two below are symptoms of lots of FAQ asking here in clpmisc.
It happens so often that folks will assume that it is happening yet
again. If you have looked but not found, or found but didn't understand
the docs, say so in your article.
Asking a Frequently Asked Question
It should be understood that you may have missed the applicable FAQ
when you checked, which is not a big deal. But if the Frequently
Asked Question is worded similar to your question, folks will assume
that you did not look at all. Don't become indignant at pointers to
the FAQ, particularly if it solves your problem.
Asking a question easily answered by a cursory doc search
If folks think you have not even tried the obvious step of reading
the docs applicable to your problem, they are likely to become
annoyed.
If you are flamed for not checking when you *did* check, then just
shrug it off (and take the answer that you got).
Asking for emailed answers
Emailed answers benefit one person. Posted answers benefit the
entire community. If folks can take the time to answer your
question, then you can take the time to go get the answer in the
same place where you asked the question.
It is OK to ask for a *copy* of the answer to be emailed, but many
will ignore such requests anyway. If you munge your address, you
should never expect (or ask) to get email in response to a Usenet
post.
Ask the question here, get the answer here (maybe).
Beware of saying "doesn't work"
This is a "red flag" phrase. If you find yourself writing that,
pause and see if you can't describe what is not working without
saying "doesn't work". That is, describe how it is not what you
want.
Sending a "stealth" Cc copy
A "stealth Cc" is when you both email and post a reply without
indicating *in the body* that you are doing so.
Be extra cautious when you get upset
Count to ten before composing a followup when you are upset
This is recommended in all Usenet newsgroups. Here in clpmisc, most
flaming sub-threads are not about any feature of Perl at all! They
are most often for what was seen as a breach of netiquette. If you
have lurked for a bit, then you will know what is expected and won't
make such posts in the first place.
But if you get upset, wait a while before writing your followup. I
recommend waiting at least 30 minutes.
Count to ten after composing and before posting when you are upset
After you have written your followup, wait *another* 30 minutes
before committing yourself by posting it. You cannot take it back
once it has been said.
AUTHOR
Tad McClellan and many others on the comp.lang.perl.misc newsgroup.
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/"
------------------------------
Date: Mon, 18 Jan 2010 22:24:44 -0800
From: Wanna-Be Sys Admin <sysadmin@example.com>
Subject: Re: search and replace in Perl
Message-Id: <Mec5n.6833$5m.6830@newsfe12.iad>
Dominic Philsby wrote:
> Hi, I'm using Perl to do simple text search & replace within a text
> file. The Perl version, sample file, and commandline syntax I am using
> is shown below.
>
>
> C:\test>
> C:\test>
> C:\test>type file.txt
> the quick brown cow jumps over the lazy horse
> C:\test>
> C:\test>
> C:\test>perl -p -e "s/cow/fox/g;s/horse/dog/g" file.txt
> the quick brown fox jumps over the lazy dog
> C:\test>
> C:\test>
> C:\test>perl -v
>
> This is perl, v5.6.1 built for MSWin32-x86
>
> Copyright 1987-2001, Larry Wall
>
> Perl may be copied only under the terms of either the Artistic License
> or the
> GNU General Public License, which may be found in the Perl 5 source
> kit.
>
> Complete documentation for Perl, including FAQ lists, should be found
> on
> this system using `man perl' or `perldoc perl'. If you have access to
> the
> Internet, point your browser at http://www.perl.com/, the Perl Home
> Page.
>
>
> C:\test>
> C:\test>
> C:\test>
>
>
> My file.txt document contains only one line but the real files are
> several hundred thousand lines.
> The words I am changing are not just "cow" and "horse" but hundreds of
> words.
>
> I am using Windows.
>
> In my commandline program, my question is rather than specifying "s/
> cow/fox/g;s/horse/dog/g" on the commandline, I want to reference a
> file containing this. In otherwords, I want my commandline program to
> reference a text file, lets call it regexReplace.txt, containing the
> following
>
> s/cow/fox/g;
> s/horse/dog/g;
>
> Can someone help me out with the syntax or how to do this?
> Thank you
>
> Dominic
So, step through the file line by line (or read it into an array, but
that's usually not preferred if the file is very large) and for each
line, do what you want.
open the file.
while
s///;
open(my $textfile, '<', 'regexReplace.txt') or die $!;
while (<$textfile>) {
s/cow/fox/g;
s/horse/dog/g;
print;
}
close($textfile) or warn $!;
Are you looking to modify he file, or just replace the values on output?
The above just replaces the output. Also, assuming the file is more
important than simple, unimportant text, you will likely want to use
file locking if the file could be changed by another process while
you're viewing or changing it.
--
Not really a wanna-be, but I don't know everything.
------------------------------
Date: Tue, 19 Jan 2010 00:22:28 -0500
From: "Uri Guttman" <uri@StemSystems.com>
Subject: Re: Variable set to 0
Message-Id: <874omiis8b.fsf@quad.sysarch.com>
>>>>> "BM" == Ben Morrow <ben@morrow.me.uk> writes:
BM> Quoth "Uri Guttman" <uri@StemSystems.com>:
>> >>>>> "BM" == Ben Morrow <ben@morrow.me.uk> writes:
>>
BM> Quoth sreservoir <sreservoir@gmail.com>:
>> >>
>> >> because 0 is, traditionally, not true, even in perl where false is
>> >> canonically undef.
>>
BM> No. False in perl is canonically a dualvar that is the empty string in
BM> string context and 0 in numeric context (so there are no warnings on
BM> numeric conversion, unlike a plain "").
>>
>> i know that but the OP's issue was not knowing that 0 was false or not
>> getting that if checked for false and not defined.
BM> I know you know that, which is why I wasn't saying it to you. I was
BM> saying it to sreservoir, who apparently didn't.
then you should have replied to his post and not mine. :)
uri
--
Uri Guttman ------ uri@stemsystems.com -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------
------------------------------
Date: Mon, 18 Jan 2010 22:17:56 -0800
From: Wanna-Be Sys Admin <sysadmin@example.com>
Subject: Re: Variable set to 0
Message-Id: <o8c5n.6831$5m.1574@newsfe12.iad>
Faith Greenwood wrote:
> I have the following:
>
> use strict;
> use warnings;
>
> my $number=0;
> print "This:$number\n";
> print "That:$number\n" if $number;
>
> __END__
>
> Of the two lines that print the variable, why does it print the first
> line but not the second?
> If I change the $number to equal 1, then both lines print fine.
>
> thank you
print "That:$number\n" if defined $number;
or
print "That:$number\n" if $number ne "";
--
Not really a wanna-be, but I don't know everything.
------------------------------
Date: Tue, 19 Jan 2010 06:07:42 +0000
From: Ben Morrow <ben@morrow.me.uk>
Subject: Re: Variable set to 0
Message-Id: <equf27-udu.ln1@osiris.mauzo.dyndns.org>
Quoth "Uri Guttman" <uri@StemSystems.com>:
> >>>>> "BM" == Ben Morrow <ben@morrow.me.uk> writes:
>
> BM> Quoth "Uri Guttman" <uri@StemSystems.com>:
> >> >>>>> "BM" == Ben Morrow <ben@morrow.me.uk> writes:
> >>
> BM> Quoth sreservoir <sreservoir@gmail.com>:
>
<snip, but attributions left>
>
> BM> I know you know that, which is why I wasn't saying it to you. I was
> BM> saying it to sreservoir, who apparently didn't.
>
> then you should have replied to his post and not mine. :)
I did.
Ben
------------------------------
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Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
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------------------------------
End of Perl-Users Digest V11 Issue 2778
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