AW: Subroutine
Jyoti jcutiep...@gmail.com asked: Can anyone help me out to call all subroutines from different .pm files in a specific directory please? Maybe if you were a bit more specific about what you're tyring to do. Maybe you want to start out by looking at http://search.cpan.org/~adamk/Class-Inspector-1.24/lib/Class/Inspector.pm to figure out which methods are exported by a class. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: testing tcp connection
Kammen van, Marco, Springer SBM NL marco.vankam...@springer.com asked: I have an issue when something goes wrong with the client that's trying to connect. 9 out of 10 times this works fine, but there are odd situations where $clientip doesn't get filled in, which leaves me with a connection I can't do anything with... I tried to use close($client) to just terminate these odd connections when $clientip is empty but that doesn't work.. From my understanding of sockets (strictly limited ;-)) you'll need to call $client-shutdown( $how ): From perlfunc: shutdown SOCKET,HOW Shuts down a socket connection in the manner indicated by HOW, which has the same interpretation as in the system call of the same name. shutdown(SOCKET, 0);# I/we have stopped reading data shutdown(SOCKET, 1);# I/we have stopped writing data shutdown(SOCKET, 2);# I/we have stopped using this socket This is useful with sockets when you want to tell the other side you're done writing but not done reading, or vice versa. It's also a more insistent form of close because it also disables the file descriptor in any forked copies in other processes. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Data migration
Shlomi Fish shlo...@iglu.org.il wrote: My suggestion is to simply copy the appropriate lines from the /etc/passwd to the new /etc/passwd. ... and of course not to forget about /etc/shadow because otherwise you won't be able to login. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: array to hash array
Sharan Basappa sharan.basa...@gmail.com asked:
Can someone tell me how to convert an array to hash.
Each array entry has a row of values
e.g. a(0) = ab cd ef; a(1) = mn de fg
The hash array needs to be constructed with one of the element in the
array row as the key.
e.g. hash{ab} = cd ef - ab is a string in the array row
hash{mn} = de fg- mn is a string in the array row
Can someone comment?
This works in the obvious way (pseudocode):
for each element in the source array:
compute the hash key from the element
compute the hash value that should be stored under that key
if the hash key doesn't exist yet
store the hash value
otherwise
handle duplicate hash key
Which part is it that is giving you trouble?
HTH,
Thomas
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AW: hash arrays
Hi,
Sharan Basappa sharan.basa...@gmail.com asked:
I am reusing a code for some enhancements. According to my
understanding, it is a record with
some unique string as key and then hash array as the value.
I iterate through the array and print as follows:
foreach my $key (keys %{$abc})
{
print $key ${$abc}{$key} \n;
}
I get values such like:
val_0001 HASH(0x186c0060)
val_0002 HASH(0x187ea490)
val_0003 HASH(0x18655bc0)
val_0004 HASH(0x1880fc60)
Can someone tell me how to get the actual value instead of HASH* as
above?
Assuming that $abc is a hash reference, it works like this:
#!/usr/bin/perl -w
use strict;
# $abc is a hash reference
my $abc = {
'foo' = 1,
'baz' = 2,
'bar' = 3,
};
foreach my $key (keys %$abc)
{
print $key $abc-{$key}\n;
}
__END__
HTH,
Thomas
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AW: Compare file/dir size
HACKER Nora nora.hac...@stgkk.at wrote: Thanks for your input. Since both directories reside on different servers I would need a solution suitable for rexec. I have already thought about something like what you suggested, but then I discarded this idea because in my opinion a rexec for each file to get the stat would not be overly elegant!? I'll stand corrected... You could run sha1sum (or md5sum or whatever you have) on the list of files you transferred, then comparte the output of both runs. MfG, Thomas Bätzler -- BRINGE Informationstechnik GmbH Zur Seeplatte 12 D-76228 Karlsruhe Germany Fon: +49 721 94246-0 Fon: +49 171 5438457 Fax: +49 721 94246-66 Web: http://www.bringe.de/ Geschäftsführer: Dipl.-Ing. (FH) Martin Bringe Ust.Id: DE812936645, HRB 108943 Mannheim
AW: Query on Qunatifiers
Chandan Kumar chandan_28...@yahoo.com asked: I have query over quantifiers. Could you please explain the combination of operators Question mark (?),dot(.),star(*),plus(+). Say this is my string: $_ = this is my first pattern ,quite confused with quantifiers ex: (thi.*?) or (thi.+?) etc I know what each operator does if used seperately,but combination of these operators are confusing. You should really read the provided documentation - Uri posted about that to the list just a short while ago ;-) Please note that . is not a quantifier. ?, + and * are. In RE, a . by itself is the atom that matches any one character. The quantifiers mean: ? 0 or 1 occurences of the previous expression. + 1 or more occurrences of the previous expression (greedy match). * 0 or more occurrences of the previous expression (greedy match). *? 0 or more occurrences of the previous expression (parsimonious match). +? 1 or more occurrences of the previous expression (parsimonious match). The difference between greedy and parsimonious matching is that in a greedy match, the longest possible match will be tried first whereas in a parsimonious match, the shortest match will be tried first. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: question abt array
Chaitanya Yanamadala dr.virus.in...@gmail.com asked:
i am in a situation like i have a scalar $value = 5
now i need to create an array with the number i mean $value
how can i do it??
Don't even think about messing with the symbol table, use a hash variable
instead:
my %hash;
my @array = qw(foo baz bar);
my $value = 5;
# store reference to an array in the hash element $key
$hash{ $value } = \...@array;
$hash{ 7 } = [ 'eni', 'miney', 'moo' ];
# accessing data, e.g. 1st Element in array 5.
print $hash{ 5 }-[0];
Using a hash makes sure there are no unwanted side effects like you
accidentally overwriting some variable required elsewhere.
If you gave a better description of what you wanted to achieve - as opposed to
what you think you need to do - I'm sure people here would be able to help you
better.
HTH,
Thomas
AW: Multi page form - cgi
Herb patyoun...@hotmail.com asked:
I've been working on putting together a multi-page form in a single
perl script. I have everything working as a single page form (writing
to mysql database and emailing the output upon submit) but have not
had any luck breaking the form into multiple pages. As mentioned
before, I'm not an everyday perl programmer so I may be going about
this whole thing wrong.
I'm trying to break 20 parameters into 4 pages as:
if ($param1 eq ) {
display page1
} elsif ($param6 eq ) {
I'd suggest that you use one CGI parameter for page selection. My personal
preference is to call it action and give it meaningful values, like:
use CGI;
use CGI::Carp qw/fatalsToBrowser/;
my $q = CGI-new();
[...]
my $action = $q-param('action') || '';
if( $action eq update ){
# display update page
} elseif( $action eq insert ){
# display insert data page
} else {
# display start/login page
}
Using a single action parameter avoids ambiguities when deciding which page
to display.
HTH,
Thomas
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AW: Multiple background processes
HACKER Nora nora.hac...@stgkk.at asked:
I am currently having an issue with background processes. I already
searched the web and found a way how to principally send a process into
background, wait for the execution to finish and then go on with the
main program:
my $pid = fork;
if ( $pid ) {
wait;
print done.\n;
} else {
print starting.\n;
system compress *.dbf ;
exit;
}
The done. is being issued at the correct point of time, namely when
really all files have been compressed. Unfortunately, this only
compresses one file after the other and therefore lacks performance. So
I tried to send multiple processes into background and have them to be
executed simultaneously. I tried the following:
my $pid = fork;
if ( $pid ) {
wait;
print done.\n;
} else {
print starting.\n;
foreach ( glob *.dbf ) {
system compress $_ ;
exit;
}
Have you had a look at the perlipc manpage yet? I'd say it's mandatory reading
for what you're trying to achieve.
Apart from that, spawning multiple cruncher processes makes sense - up to a
point. Obviously you don't want to spawn more processes than the number of CPU
cores in your system because then they would be in contention for CPU.
Fortunately, there's already at least one module on CPAN that does most of the
hard work for you:
http://search.cpan.org/~dlux/Parallel-ForkManager-0.7.5/ForkManager.pm
HTH,
Thomas
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AW: A subroutine to find every occurrence of a substring in a string?
Peng Yu pengyu...@gmail.com asked:
I can't find an existing perl subroutine (in the library) to find
every occurrence of a substring in a string. The following webpage
Example 3b. How to find every occurrence uses a loop to do so. But
I'd prefer a subroutine. Could you let me know if such a subroutine is
available in perl library?
If there isn't one, just roll your own:
#!/usr/bin/perl -w
use strict;
sub find_match {
my( $text, $match, $offset ) = @_;
$offset ||= 0;
if( $[ - 1 ( $offset = index( $text, $match, $offset ) ) ){
return( $offset, find_match( $text, $match, $offset+1) );
}
}
my $text = 'abaabaabaaababaaabaaabaababaabbbaabaabaaab';
my $match = 'aab';
print matches found at: , join(', ', find_match( $text, $match ) ), \n;
__END__
HTH,
Thomas
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AW: Perl file with arguments
Gopal Karunakar gk.kalipuray...@gmail.com asked:
How can i declare a simple perl script file which will take
arguments from the user? an example will be take two numbers and
give the sum as output.
Do you want to pass the arguments on the command line or prompt for them after
starting your script?
In the first case use the @ARGV array. Its elements are the arguments your
program was started with, e.g.
#!/usr/bin/perl -w
use strict;
if( 2 == @ARGV ){
my $sum = $ARGV[0] + $ARGV[1];
print The sum of $ARGV[0] and $ARGV[1] is $sum.\n;
} else {
# wrong number of arguments
print Usage: $0 number number\nprints the the sum of two numbers passed
as arguments\n;
}
__END__
In the second case, use the STDIN filehandle, e.g.
#!/usr/bin/perl -w
use strict;
print Enter a number: ;
chomp( my $sum1 = STDIN );
print Enter a second number: ;
chomp( my $sum2 = STDIN );
my $sum = $sum1+$sum2;
print The sum of $sum1 and $sum2 is $sum.\n;
__END__
Input sanitation and validation in these examples is left as an exercise for
the reader ;-)
HTH,
Thomas
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AW: an odd conditional statement
sillymonkeysoftw...@gmail.com sillymonkeysoftw...@gmail.com asked:
I'm working with some customizable data from a config file, and can't
for the life of me figure out how to test conditionals from an
external source.
Does anyone have an idea how to accomplish something like:
my $statement = 1 10 and 2 10; # obviously false
my $result = ($statement) ? 1 : 0;# conditional test
Now, $result will always be true(1), because the conditional is
really, in effect, just validating that $statement is a defined
scalar, not testing the statement.
But, how can I perform an actual conditional statement on this?
What I really want is:
(1 10 and 2 10) ? 1 : 0;
You can do something like
my $cond = eval( $statement );
if( $@ ){
# an error occurred while evaluation $statement
#
} else {
# $statement was o.k.; normal program flow
my $result = eval($statement) ? 1 : 0;
# rest of code
}
The two important things to keep in mind:
1) Make sure you sanitize $statement very carefully. Otherwise people can run
arbitrary perl commands and you probably don't want that.
2) Check $@ after calling eval to see wether the code could be executed or
wether it caused an error.
HTH,
Thomas
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AW: Value betwwen quotes
Chaitanya Yanamadala dr.virus.in...@gmail.com asked:
i have a string like this
ComposedBlock ID=ZONE1-2 STYLEREFS=PAR1 HEIGHT=1062 WIDTH=1986
HPOS=573 VPOS=3003
i need to get the values between the after the ID= . So how can i
do it, Can any one help me??
Assuming the string is on a single line:
#!/usr/bin/perl -w
use strict;
use warnings;
my $line = 'ComposedBlock ID=ZONE1-2 STYLEREFS=PAR1 HEIGHT=1062
WIDTH=1986 HPOS=573 VPOS=3003';
if( my( $id ) = ( $line =~ m/\s+ID=([^]*)/ ) ){
print id value is '$id'\n;
} else {
print no match found!\n;
}
__END__
Note that this method is fine for quickly grabbing a single value from a
string, but highly unsuitable for parsing a complex xml document.
HTH,
Thomas
AW: Find duplicates in an array
Gopal Karunakar gk.kalipuray...@gmail.com asked:
I needed to find all the duplicate values in an array and their count
of occurences. Any help would be appreciated .
#!/usr/bin/perl -w
use strict;
my @array=qw(foo baz bar foo baz foo);
my %seen;
foreach my $item (@array){
$seen{$item}++
}
foreach my $item (keys %seen){
print item $item seen $seen{$item} times.\n
}
__END__
HTH,
Thomas
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AW: Developer docs
Hi, Steve Bertrand st...@ipv6canada.com asked: Is there a POD system that can be used exclusively for 'developer' documentation? Can I make devel docs 'hidden' from the rest of the POD? If not, can you recommend a decent practice that I can weave into my current documentation methodology so that people can still enjoy my user docs, while I can review my devel docs within a separate `perldoc' page? Since you said weave... maybe you can use http://www.perl.com/pub/a/tchrist/litprog.html as a launch pad ;-) Cheers, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Using Arrays and if loops together
Hello Niall, niallheavey niallhea...@gmail.com wrote: I'm very new to perl but I will try to explain where I am at the moment. Providing sample input and output is fine. However, if you need help with your code people here have to be able to look at it. Try and post a minimal example for the problem you're having - who knows, by trying to isolate the problem you might even find the solution yourself ;-) Cheers, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Good/best practice - pre-declare variables
HACKER Nora nora.hac...@stgkk.at wrote:
Obviously, my point wasn't clear enough, I'm sorry for that. The
variable in the code extract that I'm really bothering about is the
$sdb: It is needed in the SWITCH of a sub-function, but this construct
only works if I pre-declare the $sdb in the calling function backup(),
even if it isn't needed for a $mode eq b but only for r.
Let's see if I understand this correctly:
You have a global variable $mode that's deciding the mode of operation in your
sub dblog(), to quote:
# DBLOG sub-function
sub dblog {
my ( $backup, $dbvers, $sdb ) = @_;
SWITCH: {
( $mode eq b ) do {
print $fh_dblogsql insert into dbmovelog (DEBENAME, MOVE,
FELD1, FELD2, ERSTELL_TS) values ('.$db.', '.$mode.', '.$backup.',
'.$dbvers.', sysdate);;
last SWITCH;
};
( $mode eq t ) do {
print $fh_dblogsql insert into dbmovelog (DEBENAME, MOVE,
FELD1, FELD2, ERSTELL_TS) values ('.$db.', '.$mode.', '.$sdb.',
sysdate);;
last SWITCH;
};
}
}
Depending on the value of $mode, you run two slightly different SQL statements.
The second of them with the wrong number of values ;-)
From the look of things, $backup and $sdb are really the same thing, namely
input for the column FELD1.
My gut feeling is that you should pass $mode as an argument to the function
since it's never nice to have a subroutine that does two different things
without an obvious reason.
I'd then coalesce $backup and $sdb into the variable $feld1 and suddenly you
don't need your switch anymore.
Apart from that, there's really no need to call a three argument function with
three arguments when you know you don't need the third argument.
Just call it with two arguments in that case, and the troublesome variable will
be set to undef.
HTH,
Thomas
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AW: print sub code
Tech list tech_l...@womenshealth.com asked: Let's say I have a module XYZ with a sub in it call ABC. I'd like to print the source code of XYZ::ABC. My reason for this is I accidentally overwrote a module with an older version, but I still have httpd running which has it loaded in memory. You can't print the source code since it's gone at that point. All that remains is the bytecode representation of that module. You can poke around in that using the B:: group of modules, like http://search.cpan.org/~jesse/perl-5.12.1/ext/B/B.pm. Beware, this is not for the faint of heart. HTH, Thomas PS: Rule #1 of system administration and programming: _always_ make a backup. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: data dumper
Bob McConnell r...@cbord.com asked: mBy saving the output of Data::Dumper to a *.pm file, it can be reloaded mvia use. What is the difference between this and exporting a YAML file? Where would either be preferred over the other? You don't need a YAML parser to read in a Perl source file. OTOH, it's easier to shoot yourself in the foot that way. MfG, Thomas Bätzler -- BRINGE Informationstechnik GmbH Zur Seeplatte 12 D-76228 Karlsruhe Germany Fon: +49 721 94246-0 Fon: +49 171 5438457 Fax: +49 721 94246-66 Web: http://www.bringe.de/ Geschäftsführer: Dipl.-Ing. (FH) Martin Bringe Ust.Id: DE812936645, HRB 108943 Mannheim -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Hash with variable name
HACKER Nora nora.hac...@stgkk.at wrote:
The script is being started with a parameter $stp (among others) that
can be one of mvb/pkv/av/be/vvw. This parameter is used as a key for a
master hash the values of which are names of other hashes themselves.
# Master-Hash
my %stp_dirs = ( mvb = mvb_dirs,
pkv = pkv_dirs,
av = av_dirs,
be = be_dirs,
vvw = vvw_dirs );
# AV
my %av_dirs=( dir11 = dir12
dir13 = dir14 );
# BE
my %be_dirs=( dir21 = dir22
dir23 = dir24 );
# MVB
my %mvb_dirs= (dir31 = dir32
dir33 = dir34 );
# PKV
my %pkv_dirs=( dir41 = dir42
dir43 = dir44 );
# VVW
my %vvw_dirs=( dir51 = dir52
dir53 = dir54 );
Try:
#!/usr/bin/perl -w
use strict;
# AV
my %av_dirs=( 'dir11' = 'dir12',
'dir13' = 'dir14' );
# BE
my %be_dirs=( 'dir21' = 'dir22',
'dir23' = 'dir24' );
# MVB
my %mvb_dirs= ('dir31' = 'dir32',
'dir33' = 'dir34' );
# PKV
my %pkv_dirs=( 'dir41' = 'dir42',
'dir43' = 'dir44' );
# VVW
my %vvw_dirs=( 'dir51' = 'dir52',
'dir53' = 'dir54' );
my %stp_dirs = ('mvb' = \%mvb_dirs,
'pkv' = \%pkv_dirs,
'av' = \%av_dirs,
'be' = \%be_dirs,
'vvw' = \%vvw_dirs );
while ( my($sdir,$tdir) = each %{$stp_dirs{'mvb'}}) {
print(SourceDir: $sdir\t\tTargetDir: $tdir\n);
}
__END__
HTH,
Thomas
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AW: Hash with variable name
HACKER Nora nora.hac...@stgkk.at asked:
Try:
my %stp_dirs = ('mvb' = \%mvb_dirs,
'pkv' = \%pkv_dirs,
'av' = \%av_dirs,
'be' = \%be_dirs,
'vvw' = \%vvw_dirs );
while ( my($sdir,$tdir) = each %{$stp_dirs{'mvb'}}) {
print(SourceDir: $sdir\t\tTargetDir: $tdir\n);
}
Is that 'mvb' intentional? Also, I don't understand why to put '\%' in
front of the values from the master hash. Nevertheless, I tried the
alterations as suggested but the error remains:
Can't use string (%mvb_dirs) as a HASH ref while strict refs in use
at /opt/data/magna/wartung/tools/get_lieferung.pl line 145.
If you use strict; you may not use symbolic references, i.e. (mis)use a
variable's name to create a reference to it. That's why I fixed your code
by replacing the variable names with references to the variable I assumed you'd
wish to address.
Maybe you should take a look at the perlref manpage (e.g.
http://perldoc.perl.org/perlref.html) for a better explanation.
As for putting in a literal 'mvb' that was just to demonstrate the usage. Of
course you can replace that with any expression evaluating to any key of
%stp_dirs or whatever.
HTH,
Thomas
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AW: Hash with variable name
HACKER Nora nora.hac...@stgkk.at asked:
Thanks for your explanation and the reference to perldoc, I understand
now. But it doesn't work yet, I still get the same error. I have
altered my source now as follows:
my %stp_dirs = ( mvb = \%mvb_dirs,
pkv = \%pkv_dirs,
av = \%av_dirs,
be = \%be_dirs,
vvw = \%vvw_dirs );
[...]
my ($sdir, $tdir);
while (($sdir,$tdir) = each %{$stp_dirs{$stp}}) {
DEBUG(SourceDir: $sdir\t\tTargetDir: $tdir\n);
}
Did I misunderstand anything?
Yes, you're using double quotes around the hash references.
Note how I wrote it:
my %stp_dirs = ('mvb' = \%mvb_dirs,
'pkv' = \%pkv_dirs,
'av' = \%av_dirs,
'be' = \%be_dirs,
'vvw' = \%vvw_dirs );
Cheers,
Thomas
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AW: fork, read from child process and timeout
Weizhong Dai weizhong@gmail.com asked:
-
$pid = open(README, program arguments |) or die Couldn't fork:
$!\n;
while (README) {
# ...
}
close(README)
--
my problem is: I read from README, but if waiting for next input is
timeout, end reading. Is there any timer or method I could use for
this purpose?
This code is probably better written as
my $program = ...;
my @arguments = ...;
my $pid = open( my $readme, '-|', $program, @arguments) or die Can't fork
'$program': $!;
while( $readme ){
...
}
close( $readme );
(code OTTOH, please excuse any typos)
i.e.
- use lexical variables
- don't use a typeglob for your filehandle, use a lexical variable instead
- use three-argument open for increased safety
As for the timeout question, I assume what you want to do is this:
- read input from $program
- if there's no input, then stop reading after suitable timeout period
Something like that is usually done using select() as shown in the second usage
example in http://perldoc.perl.org/functions/select.html
HTH,
Thomas
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AW: sort hash with an array as the value
Owen rc...@pcug.org.au asked:
I have this statement;
foreach my $key ( keys %filehash ) {
print $key $filehash{$key}-[0]\t\t\t$filehash{$key}-[3]\t
$filehash{$key}-[2]\t $filehash{$key}-[1]\n;
}
but wish to sort the output by $filehash{$key}-[0]. Is it possible?
How do I do this?
foreach my $key ( sort { $filehash{$a}-[0] cmp $filehash{$b}-[0] } keys
%filehash ){ ... }
HTH,
Thomas
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AW: IMAP email client: style security
Eitan Adler li...@eitanadler.com wrote: I wrote a program to fetch email from a IMAP account, look to see if I sent it, if yes execute any commands in the email and email the results back to via a SMTP server. [...] 2) Secondly since this program executes commands from a potentially insecure source I'd like to know if you find any security issues with my code. I used Mail::IMAPClient::get_header($_,From) to verify that I'm sending myself commands-- is this safe? [...] No. Mail headers are easily forged. You should probably be using PGP or S/MIME to authenticate your request. The request body should also include a request seqeuence number that you could use to guard against a replay-attack where an attacker would resend an old valid mail. Cheers, Thomas
AW: Remove and substitute character in a string with a regex
Finalfire blog.h...@gmail.com asked:
Hello guys! I'm skilling regex using Perl and i've some trouble about
a simple try:
i've a string like:
$string = HELLAAABB;
and i want to manipulate in that way: HELL4O3ABB4C;You can simply
notice that when i have 3 or more occurrences of a character, i want
to substitute all the occurrences and write nC where n is how times
the character C is found on a string.
So, in regex (i think there are so many way to do it but i wish to do
with regex, just skilling...) i write:
$string =~ s/(.)\1\1+/$1/;
but how can i get the number of the occurrences in the string of that
pattern?
#!/usr/bin/perl -w
use strict;
my $string = HELLAAABB;
print $string\n;
$string =~ s/(.)\1{2,}/length($).$1/eg;
print $string\n;
__END__
HTH,
Thomas
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AW: AW: Remove and substitute character in a string with a regex
Hi Shlomi, use warnings is preferable to the -w flag. Not in my book. The command line switch turns on warnings globally, whereas the use warnings; pragma only enables them in the current lexical scope. So by using the command line switch, I get warnings about crappy third-party code, too. The only case where use warnings; might be better is if you're using a braindead shell/OS that doesn't look at the shebang line. Cheers, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: about dispatch tables
Harry Putnam rea...@newsguy.com asked:
But even though I can work with that... I'm still not seeing why the
values in @_ are not available at the call to N() inside like this:
(incomplete code)
func($val1,$val2);
sub func { %h = ( N = sub { print N(@_) . \n; } ); }
If you call the sub like this, it'll create the hash %h containing the key N
associated with a code reference to an anonymous subroutine. When that
subroutine is called it will pass its _current_ argument list to function N,
then print the returned values from that function and a line feed.
If you wanted that code reference to be called with the values of @_ at the
time of its creation, you'd have to use a closure and keep a copy of the values
in a lexical variable, probably a bit like this:
#!/usr/bin/perl -w
use strict;
sub label_closure {
my $label = shift;
return sub {
my $name = shift;
print $name, you're a $label!\n;
}
}
my $laud = label_closure(genius);
$laud-('MJD');
__END__
HTH,
Thomas
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AW: Directory sizes
HACKER Nora nora.hac...@stgkk.at asked: Unfortunately, this does not explain the difference between the local du and the one via rexec on a remote machine. Any help appreciated. When you're getting different results then you're doing something differently ;-) For one thing, you're using just du to call the binary, so we can't be sure you're calling the same du in each case. So, when logged in on the remote machine, do which du and use the resulting fully qualified path in your rexec call. Also, look at your environment (set and alias) on the remote machine to see wether you're getting additional options that way. MfG, Thomas Bätzler -- BRINGE Informationstechnik GmbH Zur Seeplatte 12 D-76228 Karlsruhe Germany Fon: +49 721 94246-0 Fon: +49 171 5438457 Fax: +49 721 94246-66 Web: http://www.bringe.de/ Geschäftsführer: Dipl.-Ing. (FH) Martin Bringe Ust.Id: DE812936645, HRB 108943 Mannheim -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: How to Decode UDP packets got from libpcap using Net::Pcap
perl perlatw...@gmail.com asked: I have used libpcap to capture data using Net::Pcap module [...] This is an UDP DNS Query How can i Decode them ... Any one Please help me http://www.net-dns.org/docs/Net/DNS/Packet.html HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Array, foreach problem
Brian fulls...@me.com asked:
foreach $line (LOGFILE) {
while (my $line = $logfile) would be a better idea than
foreach $line.
Just curious for an explanation to this. I tend to use foreach too.
Don't they both accomplish the same thing? :)
foreach (LOGFILE) means that the whole file will be read into memory and
split into lines before the loop commences.
The second construct will just read in a line at a time, thus trading off speed
for memory usage.
HTH,
Thomas
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AW: about dispatch tables
Harry Putnam rea...@newsguy.com asked:
[...]
which is also inside sub dispt {the sub function}. Where does global
come in?
Hint: $code-(@_);
HTH,
Thomas
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AW: sendmail arguments
John Bruin john.br...@nec.co.nz asked: I have inherited a Perl script which sends and parses email. I am having trouble trying to figure out what the -oi and -oem arguments do in the sub below. Can anyone help? -oemode sets the ErrorMode. From http://www.sendmail.org/~ca/email/man/sendmail.html: ErrorMode=x Set error processing to mode x. Valid modes are `m' to mail back the error message, `w' to ``write'' back the error mes- sage (or mail it back if the sender is not logged in), `p' to print the errors on the terminal (default), `q' to throw away error messages (only exit status is returned), and `e' to do special processing for the BerkNet. If the text of the mes- sage is not mailed back by modes `m' or `w' and if the sender is local to this machine, a copy of the message is appended to the file dead.letter in the sender's home directory. And of course that's not a Perl question. The Perl question probably should be about how you can make your inherited code better. While TIMTOWTDI, I would like to suggest using MIME::Lite for building and sending mails - see http://search.cpan.org/~yves/MIME-Lite-3.01/lib/MIME/Lite.pm#Sending HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Interactive shell in Perl
Parag Kalra paragka...@gmail.com asked: Wanted to know if Perl has any interactive shell (just like Python, Bash, Ruby etc have) by any chance. And if yes how do we invoke that. Since you mentioned bash, the zoidberg shell might be an option: http://search.cpan.org/~pardus/Zoidberg-0.96/man1/zoid.pod HTH, Thomas
AW: get path to linked directory
Andreas Moroder andreas.moro...@sb-brixen.it asked: I have a entry in my directory that is a soft-link to another directory. Is there a way in perl to get, starting from the link, the path of the real directory ? http://perldoc.perl.org/Cwd.html#abs_path-and-friends HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Perl rounding errors?
Rob Coops rco...@gmail.com asked: I am just wondering if I sumbled upon an error in perl an error in my logic or somehtign else see the below perl one liners $ perl -e '$n = 0.945; $r = sprintf(%.2f, $n); print $r\n;' 0.94 Short answer: You shouldn't use floating point numbers for financial calculations. Instead, calculate in cent-based integer values. Long answer: perldoc -q round, perldoc perlnumber. HTH, Thomas
AW: why does this code fail with stat?
Harry Putnam rea...@newsguy.com wrote:
I'm not finding a reference in perldoc File::Find showing how to set
that flag when using the popular notation like the script involved
here.
Probably a case of not seeing the woods because of the trees ;-)
To quote:
NAME
File::Find - Traverse a directory tree.
SYNOPSIS
use File::Find;
find(\wanted, @directories_to_search);
sub wanted { ... }
use File::Find;
finddepth(\wanted, @directories_to_search);
sub wanted { ... }
use File::Find;
find({ wanted = \process, follow = 1 }, '.');
[...]
i.e.
find( {
wanted = sub {
print $_\n;
print $File::Find::name\n;
if ($lastfld eq $_) {
print $lastfld matches $_; Lets check the size:\n;
my $size = (stat($File::Find::name))[7];
print $File::Find::name size: $size\n;
}
},
no_chdir = 1,
},
$dir2
);
HTH,
Thomas
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AW: Newbie stuck at the first hurdle
Kryten kryte...@googlemail.com asked:
This is embarrassing.
All I want to do is read the content of a simple 10 line .txt file
into an array
and print out the lines, and I just can't seem to get it to work!
/*
$target = D:\testfile.txt;
open NEWBIE, $target;
@arr = WAWA;
foreach $line (@arr) {
print $line\n;
}
close(NEWBIE)
*/
#!/usr/bin/perl
# always turn on warnings and enforce strict
use strict;
use warnings;
# use lexical variables.
# modern Win32 knows about normal path separators, i.e. / instead of \
# use single quotes unless you want to interpolate the string i.e.
# include variables or escape sequences.
my $target = 'd:/testfile.txt';
# use a three argument open, use a lexical variable as a filehandle,
# check for result and die() giving an error on failure.
open( my $fh, '', $target ) or die Can't open '$target': $!;
# read the array from the filehandle you opened before
my @array = $fh;
# closing files is optional, but we're not messy programmers...
close( $fh );
foreach my $line (@array){
# $line already has cr/lf; no need to add one more
print $line;
}
__END__
HTH,
Thomas
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AW: Meta: Nice Perl?
HACKER Nora nora.hac...@stgkk.at asked: I wonder if some of you are in the same situation like me: I am the only Perl programmer in the company, at least trying hard to get along :-), but I have nobody to ask for help. So I spend hours and hours with my book and the internet when I'm stuck. Luckily, so far I almost always accomplished what I wanted to do, but I don't know whether it is good programming - the scripts work, but if I compare them to some code that comes from the experienced guys here on the list they just look ... uhm, different ... How do you improve your scripts and in general your coding style without having someone to alert/advise you what could be improved? - Many guidelines for good programming style apply to all programming languages in general - with the corollary being that the determined Real Programmer can write Fortran programs in any language[1]. Asking an experienced colleague about the subject might get you helpful pointers. - Learn from other people's code. Try and figure out why they do certain things in certain ways. Code posted to this list by major contributors usually comes with an explanation why things were done in a certain way. - Learn from your own mistakes, and find strategies to avoid or detect them. For example, back when I started learning C, I used to mix up = and == in comparisons. This led to many frustrating bug-hunts until I finally figured out that it's helpful to place constants on the left side in a comparison, so that I'd get a compiler error when I mistyped a comparison. - Get in touch with other Perl programmers. I don't know where you're located in Austria but at least in Innsbruck and Vienna, there are Perlmonger groups. Attend a Perl conference like the annual German Perl Workshop[2] or YAPC::Europe[3] - they're very reasonably priced, so that you might even be able to convince your boss to pay for the trip as a training session. HTH, Thomas 1) http://www.pbm.com/~lindahl/real.programmers.html 2) http://conferences.yapceurope.org/gpw2010/ 3) http://conferences.yapceurope.org/ye2010/ -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: AW: why does this code fail with stat?
Harry Putnam rea...@newsguy.com asked:
I pointed to that exact piece of code then asked how to make that
kind of options setting when using this format of find()
find(
sub {
if(bla){
blabla
}
},
@dir
);
That's not possible, since there is neither an option parameter nor class
variable by which you could change the behavior globally.
Your proposed code
find( {
wanted = sub {
print $_\n;
print $File::Find::name\n;
if ($lastfld eq $_) {
print $lastfld matches $_; Lets check the size:\n;
my $size = (stat($File::Find::name))[7];
print $File::Find::name size: $size\n;
}
},
no_chdir = 1,
},
$dir2
);
doesn't do that.
It does however work as intended ;-)
HTH,
Thomas
AW: How to manage large Conditional Statement
Mimi Cafe mimic...@googlemail.com asked:
I need to evaluate a statement in an if, elsif, else block, and the
statement to evaluate in the elsif is too large as I need to run a SQL
query and act on the return value.
What would be a better way to achieve this? Putting the SQL statement
elsewhere outside the block cannot be right, so I am wondering what to
do here.
I'm talking for myself here, but the way I usually do this is that I wrap up
each SQL query or set of related SQL queries in a subroutine.
If the sub's going to be used as a predicate I make sure it returns true/false
and pass all of the relevant data as arguments. By giving it a suitable name, I
end up with nicely readable code like
[...]
if( isSomeCondition( $foo, $baz, $bar ) ){
[...]
More or less straight out of Perl Best Practices, Chapter 3.
HTH,
Thomas
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AW: Is there any method to tell different between warning and errors?
Jeff Pang armyw...@gmail.com wrote: On Tue, Apr 20, 2010 at 1:28 PM, Weizhong Dai weizhong@gmail.com wrote: Hi all, In my script, I have a system call, and redirect the stderr to a file. # # open STDERR, $workpath\\error_log.txt; # system ...; # but I only want the ERROR messages to be logged in the file. Is there try this: system command arguments 2error.txt; That's exactly the same as re-opening STDERR, so it's not gonna help the OP. So how to differentiate between warning and error message? It all depends on the program's output. If the error messages are clearly tagged as such, one might try to filter STDERR by using IPC::Open3 to run the system command. That'll give the OP a distinct STDERR filehandle which he can read and parse, writing the interesting stuff to a logfile. HTH, Thomas
AW: Problems with show tech using the Net::Telnet Module
Asterix lange.gerh...@gmail.com asked:
I've made a little script to capture the output of networking
devices.
Everything works fine, until I use the show tech command in an Cisco
device.
Have you considered using the cmd() method of Net::Telnet? It has the option to
individually set a reply timeout for each command:
#!/usr/bin/perl -w
use strict;
use Net::Telnet;
my $host = '42.42.42.42';
my $sysname = 'cisco';
my $login_pw = 'letmein';
my $enable_pw = 'secret';
my $tn = Net::Telnet-new( Host = $host ) ){
$tn-waitfor( '/word: $/' );
$tn-cmd( String = $login_pw, Prompt = /$sysname\$/ );
$tn-cmd( String = 'enable', Prompt = '/word: $/' );
$tn-prompt( /$sysname#\$/ );
$tn-cmd( String = $enable_pw );
$tn-cmd( String = 'terminal length 0' );
my @data = $tn-cmd( String = 'show tech', Timeout = 60 );
print @data;
__END__
Works fine for me on a 7206. YMMV.
HTH,
Thomas
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AW: Can't locate object method TIEHASH via package Apache::Session::MySQL
Owen rc...@pcug.org.au wrote:
On Mon, 19 Apr 2010 00:14:44 +0100
Mimi Cafe mimic...@googlemail.com wrote:
I get following error when trying to open a session using
Apache::Session::MySQL.
Here is what I have
38 tie %session, Apache::Session::MySQL, undef,{
There is leading whitespace in the class name Apache::Session::MySQL.
I really don't know, but the documentation shows;
tie %hash, 'Apache::Session::MySQL', $id, {
Handle = $dbh,
LockHandle = $dbh
};
So did you try just the single quotes?
@Owen: If you really don't know then your suggestions are cargo cult
programming. Please don't do that.
As a rule of thumb, use single quotes if you're dealing with a literal string
than you don't want/need to interpolate (substitute variables, escaped
characters, etc.) and use double quotes otherwise.
MfG,
Thomas Bätzler
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Germany
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Fax: +49 721 94246-66
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AW: Writing Perl scripts to run on any OS'es
newbie01 perl newbie01.p...@gmail.com asked:
Am wanting to change my Perl scripts to get it to run on several UNIX
flavours and Windows. At the moment, the only way I can think of how to
accomplish that is always having the following checks on each and every
sub that I have.
Can anyone please suggest if there is a better way of doing this
besides what am doing now? Am not sure whether creating a module
for each OS to use is the solution although I don't know how to create
a module anyway. I found one tutorial and get lost somewhere along the
way on how to create a module ... :-)
if ($^O eq 'MSWin32') {
system dir $ARGV[0];
}
Either this is a bad example or you're doing something wrong - listing a
directory works well using the opendir()/readdir() commands in conjunction with
the File::Spec::* family of modules for parsing and constructing path names.
It's probably much less of a PITA to work with, too, since you don't have to
parse 17 different output formats.
For other stuff, you should leverage the power of CPAN - search.cpan.org is
your friend. For disk space usage for example, you might be able to use
http://search.cpan.org/~iguthrie/Filesys-DfPortable-0.85/DfPortable.pm
As for creating your own modules, have you tried perldoc perlboot?
The absolute minimum to make and use your own modules goes something like this:
Decide where you want to keep your modules. For small projects I prefer to keep
them in a directory called lib in the same directory as my Perl scripts. Perl
needs to be told about that path, so I use the following code snippet in the
header of my scripts:
use File::Spec::Functions qw( catpath splitpath rel2abs );
use lib catpath( ( splitpath( rel2abs $0 ) )[ 0, 1 ], 'lib' );
This tells perl to look first in my local lib directory that's in the same
directory as the script (wherever that is).
Decide on your module namespace and the module name. Of course you're free to
name your modules whatever you like, but the smart way is to create a hierarchy
of names that identifies the module and its purpose, and add your company name
or another unique identifier at the top level. So if you work for Quux, Inc.
and you're writing a module that implements the Froob network protocol, you
might want to name the module Quux::Net::Froob.
Note that the module name that you're going to use; must be reflected in the
file's path name. So if you decide to keep your Quux::Net::Froob module in the
subdirectory lib, it's relative path name would be lib/Quux/Net/Froob.pm.
Please note that casing and spelling must be identical between module name and
file path.
As to the contents of the module, a good starting point might be:
package Quux::Net::Froob;
use strict;
use warnings;
sub new {
my $class = shift;# 1st argument is class name
my $self = { }; # use empty anon hash to store instance
variables
bless($self, $class); # bless the hash ref into an object
return $self;
}
sub set {
my($self, $data) = @_;
$self-{'data'} = $data;
}
sub get {
my($self) = shift;
return $self-{'data'};
}
1;
__END__
The 1; at the end of the module code is recommended since the module won't
load if it's code doesn't evaluate to a true value during import.
To test your own module, try
#!/usr/bin/perl -wl
use strict;
use File::Spec::Functions qw( catpath splitpath rel2abs );
use lib catpath( ( splitpath( rel2abs $0 ) )[ 0, 1 ], 'lib' );
use Quux::Net::Froob;
my $foo = new Quux::Net::Froob;
$foo-set('blarg.');
print $foo-get();
__END__
If you're looking for a good book on Perl OO programming, I can personally
recommend Object oriented Perl by Damian Conway
(http://books.perl.org/book/171).
Hope this helps to get you started,
Thomas
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AW: Problem in installing ActivePerl 5.10 on Windows 7 with x64 chipset
Hi, Rene Schickbauer rene.schickba...@gmail.com wrote: For me, the msi packages worked quite well for the last few years. Altough i'm currently using the x86 versions due to some trouble with a few packages - mostly the ones that link to an external closed-source library, but i also had troubles with DBD::Pg. As far as I can tell, the x64 version also ships without PerlScript support (perlse.dll). Has anybody here successfully used the PerlScript engine of the x86 version on a x64 Windows system? If yes, pointers are appreciated ;-) Cheers, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Copy file from one server to another
Chris Coggins cacogg...@cox.net asked: I need to copy a small config file from one server to another. I'm generating the file on one server with a pretty complex script. I need to put that file on another server for immediate user access via html. I've tried just writing the file straight to the new server over the network using absolute paths but it doesn't work. I'm thinking that I can accomplish this instead through a perl-generated html page, to have the script copy the file from its source server and put it locally for use within the web page. What would the code look like to do this? Let's see if I got this right: You have one server where some file is generated, and another one where said file is to be downloaded from. Is this file personalized for each user, i.e. must arguments be passed from front- to backend? If it's not personalized, can or should the file be cached on the frontend for period of time? If the generation of the file is complex, can it be produced on demand or do we have to implement some kind of waiting mechanism that keeps the user's browser connected to the frontend while the file is generated? Cheers, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Perl get host's IP
pen...@nsbeta.info asked: Is there a general way to get linux OS's bound ip addresses? for example, the IP on eth0, eth1 etc. Thanks. http://search.cpan.org/~lds/IO-Interface-1.05/Interface.pm could be a good enough solution for you. I say good enough since it gives you all of the info that you'll get from ifconfig, which means that it's unaware of secondary ip addresses bound directly to the interface without using an interface alias like ethx:y. For that, you'll still need to parse the output from ip addr show (The command ip is part of the iproute2 suite, see http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2). HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: html print
Chris Coggins cacogg...@cox.net asked:
I'm having trouble getting a piece of data from a form input to print
in html. Here's the relevant portion of my code
sub subroutine {
my($hash) = shift;
my($data) = $hash-{'expl'};
print Content-type: text/html\n\n;
print STOPHTML;
div class=empdataThis employee has $data/div
STOPHTML
}
[...]
I either get a 500 error or the $data string is not there as in the
first instance of code. Can someone help?
Some notes on your code:
For once, you should not be writing my($variable) in an assignment unless you
have understood its difference to writing my $variable.
To wit:
$ perl -wle 'my $data = localtime; print $data'
Mon Apr 12 11:25:22 2010
$ perl -wle 'my( $data ) = localtime; print $data'
28
Or as another example:
$ perl -wle 'sub foo { print wantarray ? List context : Scalar context } ;
my( $data) = foo()'
List context
$ perl -wle 'sub foo { print wantarray ? List context : Scalar context } ;
my $data = foo()'
Scalar context
= Using my() on the left side of an assignment creates a list context. There
are functions like localtime that return different things depending on the
context that they've been called from. Use my( $variable ) in an assignment
only if you want to grab the first item of an array and discard all of the
other data.
The other things is that you force extrapolation by saying $hash-{'expl'};.
Not only is is superfluous in most instances, but it can hurt you, too, if the
thing you're extrapolation isn't a string.
As for you initial problem, there's too little here to do an autopsy.
The list guidelines recommend that you post a minimal code sample that'll
reproduce your problem.
Without access to that sample, I can only recommend that you run your code with
use CGI::Carp qw/fatalsToBrowser/; to capture and print the error messages
you're not seeing.
HTH,
Thomas
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AW: Date calculation help/suggestion please ... when there is no Date or Time module available
newbie01 perl newbie01.p...@gmail.com wrote:
Problem 1:
- Is there a function to compare the two (2) dates so ensure that I
will always be doing future_date-past_date? At the moment, the
workaround that am doing is if I get a negative value, then that
means, I've done a past_date-future_date and need to change
the way I print the output.
If you factor out the code that prints the output into a subroutine, then
you're fine.
# pseudocode
if( $time_delta 0 ){
print_subroutine( $t1, $t2, $delta );
} else {
print_subroutine( $t2, $t1, -$delta );
}
That's actually much nicer than converting your timestamps to, say, time_t,
then doing a compare and then probably exchanging them.
Problem 2 is the bigger problem:
- Now I want to use the same script to run on a UNIX box but
unfortunately I do not have the Date::Calc module on that server.
You can basically build and install Perl modules in your home directory using
normal user privileges - that way you would not mess up the system if that's
what the sysadmin is afraid of. You can even hide that fact by using PAR / pp
to bundle up your script, the Perl interpreter and all required modules in a
single stand-alone binary that can be redistributed across machines if they're
using the same OS release and architecture.
Of course, there still might be security concerns that prevent you from doing
that. And if you want to build XS modules like Date::Calc you'll need the
compiler/libs used to build your perl binary - at least in the good old days
that meant that you had to have gcc installed.
HTH,
Thomas
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AW: String length limits?
Hi, Chris Coggins cacogg...@cox.net asked: Is there a limit to the length of a string in perl? I'm combining about 200 pieces of data into a single string and writing the string to a file and am getting some weird behaviors every once in a while. Does perl have a limit on the length of a string it writes to a simple file? In Perl, string size is limited to the amount of memory available to your process, which may be less than the amount of memory installed in your computer. Care to elaborate on weird behavior for us? Could it be a file systems problem, i.e. writing more than 4GB to a single file on a FAT32 filesystem? Does the weirdness happen in the context of a web application? If yes, could it be a file locking issue? If it's none of the above, did you run a memtest yet? HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: about beginner perl site and developing skill
What is a CMS? http://en.wikipedia.org/wiki/Content_management_system What is meant by chipcards? http://en.wikipedia.org/wiki/Chip_card HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Perl: Subroutines and use of the GD::Graph::bars; Module
alekto alekto.antarct...@gmail.com asked: I manage to generate the array from the input file, but it seems like there is something wrong with my subroutine at the end, I have been using the examples at cpan.org as an templat for this subroutine. Following is the error msg, as well as the complete script. hostname$ ./bars.pl -f age ./bars.pl: line 5: use: command not found Array found where operator expected at ./bars.pl line 90, at end of line (Might be a runaway multi-line // string starting on line 53) And the winner is... printHistogram(/@array,$filename,$histmin,$histmax,'Age'); Use \ instead of / to create a reference. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Converting 12 hour time format to 24 hour format ... a bit urgent
newbie01 perl newbie01.p...@gmail.com asked:
Unfortunately, I suddenly have to to deal with an input file where the
datetime format is 02-Apr-2010 3:41:23 p.m., i.e. DD-MON- HH:MI:SS
a.m./p.m., so now my Delta_YMDHMS does not work as expected.
You can convert from a.m./p.m. to standard 24 hours using a simple RE:
#!/usr/bin/perl -w
use strict;
while( my $line = DATA ){
$line =~ s/(\d+)(:\d+:\d+)\s+(a|p)\.m\./($3 eq
'a')?($1%12).$2:($1%12+12).$2/e;
print $line;
}
__DATA__
02-Apr-2010 12:41:23 a.m.
02-Apr-2010 12:41:23 p.m.
02-Apr-2010 3:41:23 a.m.
02-Apr-2010 3:41:23 p.m.
HTH,
Thomas
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AW: about the various styles of `open'
Harry Putnam rea...@newsguy.com asked: I see advanced users here using various styles of open(). [three argument open] Is there something beyond style that makes those methods better than what appears to be a simpler format: [two argument open] Allow me to quote perldoc -f open: The filename passed to 2-argument (or 1-argument) form of open() will have leading and trailing whitespace deleted, and the normal redirection characters honored. This property, known as magic open, can often be used to good effect. A user could specify a filename of rsh cat file |, or you could change certain filenames as needed: $filename =~ s/(.*\.gz)\s*$/gzip -dc $1|/; open(FH, $filename) or die Can't open $filename: $!; Use 3-argument form to open a file with arbitrary weird characters in it, open(FOO, '', $file); otherwise it's necessary to protect any leading and trailing whitespace: $file =~ s#^(\s)#./$1#; open(FOO, $file\0); (this may not work on some bizarre filesystems). One should conscientiously choose between the magic and 3-arguments form of open(): open IN, $ARGV[0]; will allow the user to specify an argument of the form rsh cat file |, but will not work on a filename which happens to have a trailing space, while open IN, '', $ARGV[0]; will have exactly the opposite restrictions. I hope this answers your question ;-) Cheers, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Working with files of different character encodings
Doug Cacialli doug.cacia...@gmail.com asked:
Does anyone have any ideas how I can make the second block of code
work? Or otherwise accomplish the task without opening the .txt file
twice?
How large are your data files? If your available memory is much larger than
your maximum file size, you might get away with slurping the file into a scalar
and then convert its encoding if needed, possibly like this:
#!/usr/bin/perl -w
use strict;
use Encode;
my $file = 'test.txt';
open( my $fh, '', $file ) or die Can't open '$file': $!;
my $data = do {
local $/ = undef;
$fh;
};
close( $fh );
if( $data =~ m/^\xff\xfe/ || $data =~ m/^\xfe\xff/ ){
print input is UTF-16 w/ BOM\n;
$data = decode('utf-16',$data);
} elsif( $data =~ m/^[^\x00]\x00/ ){
print input is probably little-endian utf-16 w/o BOM\n;
$data = \xff\xfe . $data;
$data = decode('utf-16',$data);
} elsif( $data =~ m/^\x00[^\x00]/ ){
print input is probably big-endian utf-16 w/o BOM\n;
$data = \xfe\xff . $data;
$data = decode('utf-16',$data);
}
chomp( $data);
my @words = split /\s+/, $data;
print input file has . scalar( @words ) . words\n;
__END__
HTH,
Thomas
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AW: Perl appears to be introducing whitespace when reading .txt files
Doug Cacialli doug.cacia...@gmail.com wrote: The unicode / UTF16 issues presented by Thomas and Dr. Rudd are a little beyond me. I'm reading up now, but can someone shed some light? Let's see if I can quickly summarize: - text is made up from letters (characters). - a computer doesn't know letters, it only knows numbers (bytes). - an encoding specifies how letters are mapped onto numbers. In classic ASCII encoding, the byte value 65 represents the character A. - For a long time, the most common encodings where single-byte encodings that basically could represent up to 256 different characters. - There are also multi-byte encodings that can encode many more characters. One of those is Unicode which endeavours to be the one ring of character encodings. - There are several storage formats for Unicode. One of those is UTF-16, which encodes most of what we'd consider common characters in two bytes each, while using 4 bytes for the rest. - One of the big problem with plain text files is that there's usually no hint as to their encoding. So what we assume is happening is that your data is stored as UTF-16, where standard ASCII characters are stored as two bytes of data. Your program doesn't specify that the data is UTF-16, so perl reads it as single-byte encoded data, effectively introducing lots of null characters into the string. You now have two options: either convert your input, or modify your program to handle Unicode input. In any case you could try this snipped in your code: print NUL character found in string - input might be UTF-16\n if $line =~ m/\x00/; MfG, Thomas Bätzler -- BRINGE Informationstechnik GmbH Zur Seeplatte 12 D-76228 Karlsruhe Germany Fon: +49 721 94246-0 Fon: +49 171 5438457 Fax: +49 721 94246-66 Web: http://www.bringe.de/ Geschäftsführer: Dipl.-Ing. (FH) Martin Bringe Ust.Id: DE812936645, HRB 108943 Mannheim -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Syntax of Foreach loop
Jon Forsyth jon4s...@gmail.com asked:
I am truly a beginner. Could someone help me understand this syntax
out of a code example from Learning Perl? On line 5 I'm confused
as to why my $number is between foreach and the ()? is my
$number part of the loop?
my declares a variable for the lexical scope. While Perl by itself will
happily let variables spring into existence whenever you first refer to them,
the accepted best practice is to run perl with the -w switch or the use
warnings; pragma which requires variables to be declared before their first
use.
The foreach loop iterates over each element in the argument list passed
between the (). Unless there's a variable name between the keyword foreach and
the braces, foreach makes the default variable $_ to an alias for each of the
elements in the argument list. If there's a variable between foreach and the
braces, that variable becomes the alias instead.
Please note that I said alias instead of copy - if you modify $_ or your loop
variable, it'll change the contents of your array:
#!/usr/bin/perl -w
my @array = qw(foo baz bar);
print join(',',@array), \n;
foreach (@array){
$_ = uc($_);
}
print join(',',@array), \n;
__END__
HTH,
Thomas
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AW: AW: Syntax of Foreach loop
Uri Guttman u...@stemsystems.com wrote: TB == Thomas Bätzler t.baetz...@bringe.com writes: TB with the -w switch or the use warnings; pragma which requires TB variables to be declared before their first use. that is the use strict pragma, not the warnings one. Of course. I knew I shouldn't have posted before my first cup o' coffee ;-) Cheers, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Perl appears to be introducing whitespace when reading .txt files
Doug Cacialli doug.cacia...@gmail.com wrote: I'm completely baffled by this and not entirely sure where to start. I have a plain text file, testfile.txt, which contains a single line: Could this be an encoding issue? How big is that file? Larger than 18 or 19 bytes? If yes, http://perldoc.perl.org/perlunicode.html#When-Unicode-Does-Not-Happen may have the answer. Cheers, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Storing a Hash Inside An Array
Pry, Jeffrey jeffrey@sig.com asked:
Now, I was wondering if it would be possible to store a hash inside of
an array.
Sure, just use the anonymous hash constructor {}, i.e. like
$settings[$i] = { 'ftpserver' = localhost, 'password' = 'p...@$$word' };
Or add/change individual keys in the hash
$settings[$i]-{ 'username' } = 'anonymous';
Or store the hash inside a hash
my %host_settings = (
'localhost' = { 'password' = 'p...@$$word' },
'ftp.cdrom.com' = { 'username' = anonymous, password = 'w...@r.es' },
);
Then you could say
my $host = 'ftp.cdrom.com';
print Known settings for $host:\n
foreach my $parameter ( keys %{ $host_settings{ $host } } ){
print - $parameter: . $host_settings{ $host }-{ $parameter } . \n;
}
Or store a hash inside an array inside a hash inside an array...
push @slightly_silly_example, { 'key' = [ { 'some' = 'text' } ] };
Whatever you're doing, go check out Data::Dumper. It's invaluable when you're
hitting a snag working with nested data structures.
HTH,
Thomas
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AW: Regex question
Bruce Ferrell bferr...@baywinds.org wrote:
if ( ! defined $username || ! $username =~ /[0-9]{10,11}/ ) {
do something;
} else {
do something else;
}
what that's supposed to do is this:
if it's blank or not 10 or 11 digits...
The question is where is my understanding faulty or did I mess up.
defined() is true if the checked variable has been assigned any value except
undef, so defined $username will be true for an empty username, too.
In any case I'd probably rather write your code like this:
$username ||= ''; # make sure it's always defined
unless( $username =~ m/^\d{10,11}$/ ){
# bad username
} else {
# good username
}
HTH,
Thomas
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AW: Deleting last 10 lines of a file
sheela b sheela.b.2...@gmail.com asked:
How to delete last 10 lines of a file using Perl one liner?
I used the following one liner to delete first 10 lines of a file,
perl -i.bak -ne 'print unless 1..10' test.txt
OTTOH:
perl -i.bak -ne 'BEGIN { $b[9]= } print shift @b; push @b, $_'
test.txt
@b is the bucket chain of 10 initially empty strings. Inside the implied
while() loop, new text is added at the end of the chain while the head element
is pruned and then printed. The loop will terminate on eof(), leaving the last
10 lines of text in the array.
If you're dealing with small files, another option would be to slurp in the
file to an array, delete the last 10 items of the array and write the file back
out to disk.
HTH,
Thomas
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AW: CGI-BIN Help/Advise - editing a file - HOW ?
newbie01 perl newbie01.p...@gmail.com asked: At the moment, I have some sort of INI/config file that I edit manually via vi. These config files are simple delimited file that are used by some of the scripts running on the server. I want to be able to the same thing via cgi-bin, can anyone advise where to start. Basically, I want to be able to display the contents of the INI/config file in some kind of FORM or web page and then allow the user to be able to edit and save it at the same time. Any advise on where to start will be very much appreciated. Am not sure if I should be using PHP instead of CGI-BIN but I thought the latter would be simpler to do. Being able to prompt for a username/password prior to editing the file would be a plus ... :-) If I may start with the last question: user authorization is usually easiest handled as part of the web server configuration. If you're using Apache, look at the Location directive. Also, there's no programming language called CGI-BIN. CGI is a calling convention that defines how the web server invokes external programs to handle calls to certain URLs. Since CGI usually involves starting a new process for the external program it's less effective for either Perl or PHP than using a built-in interpreter in the web server. In PHP the latter is often called using SAPI while Perl people talk about using mod_perl. Solving your problem is possible in either language. Since this is a Perl list, we'll stick to using Perl here, though. At this point you'll probably want to look at the CGI module for all of your page rendering and argument parsing needs. Your code flow will likely look something like this: 1) Read config file into memory 2) Apply changes submitted by the user to the in-memory representation 3) Render the in-memory representation to a form where the user can edit values 4) Write out the config file data if it was changed Things to keep in mind are - You might want to do implement some kind of locking to prevent two people from editing your file ant once, since this may lead to lost updates (where changes from one user overwrite the changes previously submitted by another user) or worse (a trashed output file). - Pressing the stop button in the browser can cause your program to abort in mid-execution. You'll want to make sure that this doesn't happen while handling the update of the output file. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Please excuse the NOOB question - but I guess since this is a perl.beginners group
Hi, GlenM glenmill...@gmail.com wrote: I am sure that someone out there has done this before - I *think* I am on the right track. I have a directory full of emails. What I would like to do is read each file in, then parse them into a CSV style file. Quick aside: you can use the $. builtin variable to get the line number instead of keeping track of it yourself. Since you asked for suggestions, here's my $0.02: Putting mails line by line into a CSV files seems futile to me, since the number and position of mail headers is variable. If you want to create a database of your mails or do some other sort of data mining I would suggest that you look at something like the MIME-Tools bundle[1] to do the actual parsing and the concentrate on doing something useful with the extracted information. HTH, Thomas 1) http://search.cpan.org/~doneill/MIME-tools-5.427/lib/MIME/Tools.pm -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: newline problem
Michom michel.makhlo...@gmail.com asked: I am new to perl and I have written a smal script to grab data from one file, and put them into another file. The problem is new lines, which are printing nice under a linux environment, but it is all messed up if I open it with notepad. I am running Perl 5 under cygwin. This is a feature of Notepad - it expects DOS-style \r\n as a line ending. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Warning: Use of uninitialized value
Bob Williams n...@spam.barrowhillfarm.org.uk asked:
I am trying to split the lines in a file into two halves (at the first
space) each half going into an array. The code I have written is below.
---Code---
#!/usr/bin/perl
use warnings;
#use strict;
use strict; # unless you know what you're doing.
#use diagnostics;
# perl script to compare two files of md5 checksums
#+and extract the lines which differ
open (BHF_FILE, /home/bob/tmp/md5music)
or die Could not open md5music: $!;
Better:
open( my $bfh_file, '', '/home/bob/tmp/md5music' ) or die ...
@bhffile = BHF_FILE;
close (BHF_FILE);
for (my $i = 0; $i = $#bhffile; $i++){
$bhffile[$i] =~ m/(\s.+) ( .+)/;
push @ukchecksum, $1[$i];
push @uktrackname, $2[$i];
}
If your track names are unique, you're much better off using an associative
array (hash) for your data.
It also makes comparison with track names and checksums from a second list much
easier:
my %uktrackchecksum;
while( my $line = $bhf_file ){
my( $track, $checksum ) = split /\s+/, $line;
$uktrackchecksum{ $track } = $checksum;
}
close( $bhf_file );
print @ukchecksum[0]; # Won't print - uninitialized value ???
print @uktrackname[0];# Won't print - uninitialized value !!!
foreach my $track (keys %uktrackchecksum){
print $track = $uktrackchecksum{ $track }\n;
}
HTH,
Thomas
PS: Totally OTTOH, please excuse any typos.
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AW: passing a hash via cookie and dereferencing it
mike msmspellman...@gmail.com asked: I am trying to pass a hash of hashes from one script to another via a cookie. I can get the cookie to pass, but when I try to get the inner hash keys and values using what I think is the correct method, I cannot get them. Here are two scripts which should do it, but don't: Assuming that you do traditional CGI, each script invocation starts a new Perl process that exists after executing the script. When that happens, all your data is expunged and the hash reference you passed becomes invalid. What you want to do is called session handling and there are oodles of modules for doing that on CPAN. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: chroot as non-root?
Trevor Vallender t...@tsv.me.uk asked: I am designing a system in which scripts are installed into their own directory, by a non-root user, under their home directory. It is very important they not be allowed to write anywhere outside the directory they are installed in. There are two ways I thought of doing this; create a user for each script to run as, without permission to see outside of its directory, or run in a chroot. My problem here is both of these methods need root privileges to get started, and for the life of me I cannot think how to get around this. Is there any way at all to create a chroot-like environment without root privileges? You don't mention on which OS you're trying to implement this, but if it's Linux, then maybe SELinux (http://selinuxproject.org/page/Main_Page) might be a solution for you. When I had similar requirements in the past, I've always opted for a chroot-based solution, though - mainly because I knew I could make it work with limited effort. What I'd do is run a ssh daemon in a chroot jail and then make my unprivileged users connect to that instead of the real system. HTH, Thomas
AW: :POP3 -- download only x number of mails
Agnello George agnello.dso...@gmail.com asked: I am planning to use the Net::POP3 module to downald a mail box and then pass the mails via a parser . I would like to know if the there is a option to downlod only a certin number ( 100 ) of mails [unread] and then mark the mails as read . The mail box sie is 400 mb . And is there a way to keep the mails on the server. You can do the first two things without a problem. The third depends on the POP3 server's setup. Read mail may be expunged from the mailbox regardless of whether you requested it to be deleted or not. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: how to automate yum installation
mahesh bhasme mbha...@gmail.com asked: I want to pass yes/no argument to this comment : (Is this ok [y/N]: [y] ) . How we can do this in perl? Generally speaking, read the perlipc manpage (perldoc perlipc on the command line). In this particular instance, I'd rather suggest using yum -y instead. MfG, Thomas Bätzler -- BRINGE Informationstechnik GmbH Zur Seeplatte 12 D-76228 Karlsruhe Germany Fon: +49 721 94246-0 Fon: +49 171 5438457 Fax: +49 721 94246-66 Web: http://www.bringe.de/ Geschäftsführer: Dipl.-Ing. (FH) Martin Bringe Ust.Id: DE812936645, HRB 108943 Mannheim -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Regular expressions question
Hi,
Dermot paik...@googlemail.com suggested:
2009/11/17 mangled...@yahoo.com mangled...@yahoo.com:
Can anyone tell me hoq to write a regular expression which matches
anything _except_ a litteral string ?
For instance, I want to match any line which does not begin with
Nomatch. So in the following :
You would negate the pattern. Something like this:
#!/usr/bin/perl
use strict;
use warnings;
while (DATA) {
print if ! /^Nomatch/;
}
__DATA__
Line1
Line2
Nomatch
Line3
Line 4
One could also use a zero-with negative look-ahead assertion:
#!/usr/bin/perl -w
use strict;
while( my $line = DATA ){
if( $line =~ m/^(?!Nomatch)/ ){
print match: $line;
}
}
__DATA__
Line1
Line2
Nomatch
Line3
Line 4
Cheers,
Thomas
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AW: Perl CGI Incremental find
Hi, Jeff Pang pa...@uk2.net wrote: On Nov 17, 2009, Dave Tang d.t...@imb.uq.edu.au wrote: Is it possible to implement an incremental find* feature on a Perl CGI page? I'm running Apache2 with mod_perl on linux. For example, if I have a list of stuff (A, Aa, B, Bb, C, CA, etc. stored in a file or database) and when a user starts typing in A into the web form, 2 suggestions in a drop down menu will come up (A and Aa but not CA). Users will be able to click on this drop down menu and the web form will be filled with what they clicked on. A real life example would be Google Suggest**. This is the stuff JavaScript will do, nothing about CGI, which is a server-end implement. Yes and no. What the OP is inquiring about is a combination of technologies that are usually referred to as AJAX[1]. One possible starting point would be CGI::AJAX[2]. HTH, Thomas [1] http://en.wikipedia.org/wiki/Ajax_(programming) [2] http://search.cpan.org/~bpederse/CGI-Ajax-0.707/lib/CGI/Ajax.pm
AW: foreach loop
Anant Gupta mailto:anantgupta...@gmail.com asked:
In the foreach loop, without going to the beginning of the loop, i want
to get the next iteration of data. How do i get it.
You should probably not slurp (read in all at once) the file unless you need
to.
In your particular case reading in line by line is especially useful since this
would allow you to retrieve the next line from the file handle without having
to go to the next iteration in the loop.
Eg. (untested OTTOH though):
my $filename = 'abc.txt';
open( my $file, '', $filename ) or die Can't open '$filename': $!;
while( my $line = $file ){
if($line =~ m/something/){
if( defined( $line = $file ) ){
# do something with new line
} else {
# handle EOF here
}
}
}
HTH,
Thomas
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AW: foreach loop
Philip Potter philip.g.pot...@gmail.com asked:
Won't this loop terminate early if there is a blank line or a line
containing only '0'? If I do a readline loop I always do:
while (defined ($line = $file))
Is there something magical happening here I don't know about? I know
about the magical:
while ($file)
which is equivalent to:
while (defined($_ = $file))
but I don't know of any magic in the while loop at the top.
See the Camel book, p.81:
[...]
while( my $line = STDIN ) { print $line; } # now private
Both of these while loops still implicitly test for whether the result of the
assignment is defined, [...]
HTH,
Thomas
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AW: How do I pick one random element from an array?
Majian jian...@gmail.com asked: [...] print Array of random: $array[rand @array]\n; I thoght it might work but it doesnt. I hope someone could give me an idea to work this out... TIMTOWTDY: a) print Array of random: $array[rand( @array ) ] \n; b) print Array of random: . $array[rand @array] . \n; c) my $random_name = $array[rand @array]; print Array of random: $random_name\n; HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: AW: How do I pick one random element from an array?
Dave Tang d.t...@imb.uq.edu.au asked: Just a quick question, how does Perl interpret something like $array[0.7995038473872]? Just like $array[ int(0.7995038473872) ], i.e. the floating point number is coerced into an integer value by cutting off the decimal places. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: About the hash case insensitive ~~~
Majian jian...@gmail.com asked:
%courses = (
2CPR2B= C Language,
1UNX1B= Intro to Unix,
3SH414= Shell Programming,
4PL400= Perl Programming,
);
print \n\EDP\ NUMBERS AND ELECTIVES:\n;
while (($num, $value) = each (%courses))
{
print -\n;
printf %-10s | %s\n , $num, $value;
}
print \nWhat is the EOP number of the course you wish to take : $num;
chomp ($num = STDIN);
print The course you will be taking is: \$courses{$num}\\n;
===
The question was :
If I type the 4PL400, then it will output the value ---Perl
Programming;
But I want to type the 4pl400 , and the result should be printed Perl
Programming
How could I come it true?
Use chomp ($num = uc(STDIN) ) to uppercase the input and make sure that all
your keys are in upper case, too.
HTH,
Thomas
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AW: Building a fmt line for printf with a carriage return
Hi, Wagner, David --- Senior Programmer Analyst --- CFS david.wag...@fedex.com wrote: Here is the sample script I was playing with: #!/usr/bin/perl use strict; use warnings; my $MyLine1 = q[%2d %5s %6s]; my $MyLine2 = q[%2d %5s \n%6s]; The q// operator is equivalent to single quotes, so escape sequences like \n are not interpolated. If you want \n to be expanded to a newline character, you need to use qq or double quotes, or a combination of q// and qq// or quotes and text concatenation. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: perl document
mahesh bhasme mbha...@gmail.com asked: I am new to perl. From where I get the basic perl document Depends on your distribution, really. If you're on Windows and using the ActiveState Perl distribution, look for the html folder in your Perl installation directory. On Unix, you might want to try perldoc or man to get you started. Have a look at the perlsyn, perlop and perlrun documents (perldoc persyn etc) if you've got some programming experience. If you don't, you might be better off with supplementary documentation in book form like Learning Perl - please see http://books.perl.org/. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: compact my wordlist generator
Michael Alipio daem0n...@yahoo.com wrote: Can anyone tell me how the code above works? My original program must deal with arbitrary length and generate all the possible combinations (even repeating) of a particular set. What could take me gazillions of for loops for that, somebody just came up with less than ten lines. I can just copy and paste the code I found above but I want to learn how it works. How could someone write this code so easily but when I tried even writing just a pseudocode for it, my head almost exploded. It probably helps if you have some understanding of the underlying mathematics of the problem domain, i.e. in this case combinatorics. This would also clear up potential misunderstandings viz the definition of a permutation (randomly pick n of m elements without putting them back) vs. that of a combination (randomly pick n of m elements while putting them back). I want to be a good programmer, but at this rate, I don't think I can be one if I will just keep copying and pasting someone else's code or downloading modules from CPAN. Actually, taking somebody else's code and trying to figure out how it works is a good exercise ;-) Can anyone teach me how my own code (the one with gazillion for loops), can be converted into a pseudocode then eventually into a working sub procedure? No, probably not right away. But the good news is that most people don't come up with elegant solutions off the top of their heads - instead, they will have learned a number of basic patterns and/or algorithms for solving common problems, and they will have the experience to adapt what they know to new problems. So, in order to become a better programmer you should look at stuff people have been doing before you. Go to your local library and borrow a book on Algorithms. Try to implement them in Perl. Have a look at the Perl cookbook. If you want a challenge, then treat yourself to a copy of Higher Order Perl by Mark Jason Dominus. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: AW: compact my wordlist generator
Michael Alipio daem0n...@yahoo.com wrote:
I knew I needed a recursive function, I just didn't know how to start.
That is usually the easy part - you start out by solving the problem for a base
case, and then you embellish.
With regard to your problem of generating all combinations of a set of
elements, the base case would be to just enumerate those elements.
For a longer result set with n elements (n being 1), you'd then combine the
result for n-1 elements with the one element result set.
What confused me more is that the code I found is a lot different from
what I was initially thinking. He used the builtin function substr in the
code in a way that I couldn't figure how it worked.
If in doubt, it pays off to RTFM ;-)
So you do perldoc -f substr and it'll tell you:
You can use the substr() function as an lvalue, in which case EXPR must
itself be an lvalue.
It helps to know that lvalue is short for left-hand value and it basically
means that it behaves like a variable on the left hand side of the assignment
operator - it can be assigned a value.
The example from the man page helps to clarify this behavior:
my $name = 'fred';
substr($name, 4) = 'dy'; # $name is now 'freddy'
What's the use of double ($$) after sub perm?? Does it have anything to
do with process IDs (perldoc perlvar says so)?
Nope, these are prototypes for the function call (see perldoc perlsub, section
Prototype). Basically these two $$ signs make the function request two
arguments, which will be coerced to scalar values. This is of course only half
the truth, but I'll leave the nasty details and consequences to more erudite
folks on this list to explain ;-)
This line is also confusing:
substr($result,$cur,1)= $_;
Substr returns a list, right? The first parameter is the expression, 2nd
is the offset, and last is the length.
The above line is too cryptic for me. What confused me more is that the
return value of substr was assigned the $_.
Actually, substr() as an lvalue designates a part of the string $result that
will be assigned to, but please see above.
BTW, taking the recursive approach outlined above and using Iterators, my first
draft for a combination generator looks like this:
#!/usr/bin/perl -w
use strict;
#
# Iterator that generates all combinations of length $n of a set of elements.
#
sub gen_combo_iterator {
my( $n, @elements ) = @_;
# base case: iterator for all one element combinations
# This will just enumerate all elements of the set
if( $n == 1 ){
# this is a so-called closure - we return an anonymous subroutine that
# can still access the variables in its outer scope even though they
# are no longer visible for the rest of the program.
# subsequent calls to the anonymous function will manipulate a copy
# of the variable @elements that was created when the function was
# created by calling the outer subroutine.
return sub {
return shift @elements;
};
} elsif( $n 1 ){
# recursion: all combinations of n elements are the product
# of all (n-1) element combinations x all 1 element combinations.
# this call with fall through until it reaches $n = 1
my $sub_combo_iterator = gen_combo_iterator( $n -1 = @elements );
# the second iterator has just one element
my $combo_iterator = gen_combo_iterator( 1 = @elements );
# we pick the first element
my $element = $combo_iterator-();
return sub {
if( my $sub_combo = $sub_combo_iterator-() ){
# if the iterator over all combinations of length n-1 still
# returns a value, combine it with my current item.
return $element . $sub_combo;
} else {
# try and pick a new element from the 1 element iterator
if( $element = $combo_iterator-() ){
# if there's a new element, reset the n-1 element iterator
$sub_combo_iterator = gen_combo_iterator( $n -1 = @elements );
# get a fresh element from the n-1 element iterator
$sub_combo = $sub_combo_iterator-();
# combine with the current element and return like above
return $element . $sub_combo;
} else {
# nothing more to return, we are finished.
return undef;
}
}
};
} else {
die Assertion: $n must be a positive inter greater or equal 1;
}
}
#
# generate an iterator that will return all combinations of a given set
# with $min up to $max elements.
#
sub gen_all_combinations_iterator {
my( $min, $max, @elements ) = @_;
if( $min $max ){
my $iterator = gen_combo_iterator( $min = @elements );
return sub {
if( my $result = $iterator-() ){
return $result;
} else {
$min++;
if( $min = $max ){
$iterator = gen_combo_iterator( $min = @elements );
return $iterator-();
} else {
AW: Url written in txtfile
Hi,
Ruprecht Helms rhe...@rheynmail.de asked:
actually I have written the following line:
Currently. actually is actually a false friend.
print STATISTIKDATA
CGI-a({href='http://www.b-net-
c.de/adressbuch/$Vorname_$Name_$id.html'},'Link
zum Profil');
You are using the wrong quote marks. Use double quotes if you want variable
names in the string to be replaced by their values.
That'll raise the next problem, though: _ is a valid character for a variable
name, so the Perl interpreter will try to access the variable $Vorname_ which
probably isn't what you wanted. In such a case, use curly braces to delimit the
variable name, like this:
print STATISTIKDATA
CGI-a({href=http://www.b-net-c.de/adressbuch/${Vorname}_${Name}_$id.html'},'Link
zum Profil');
HTH,
Thomas
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AW: Url written in txtfile
Ruprecht Helms rhe...@rheynmail.de asked:
how have I to write the printstatement to write a URL like
http://www.example.com within the htmltag (a
href=http://www.example.com;Linktext/a) into a textfile.
Hm, for example
#!/usr/bin/perl -w
use strict;
my $file = '/some/path.txt';
my $text = 'a href=http://www.example.com;Linktext/a';
# naïve url extraction example. See mailing list archive for
# proper solution(s) of how to do this using a parser.
my( $url ) = ($text =~ m{a href=(.*?)});
open( my $fh, '', $file ) or die Can't open '$file': $!;
print $fh $url\n;
close( $fh )
__END__
OTTH YMMV of course.
HTH,
Thomas
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AW: Hash of Hashes
Soham Das soham...@yahoo.co.in asked:
How can I create a Hash of Hashes from two lists. Is it possible?
I want the effective functionality to be served like this
$ChildHash[Joe][21A]=Sally
i.e Joe at 21A has a child called Sally. List1 here will be the name of
Parents, List2 here will contain the house number.
Please keep in mind: square brackets are for arrays/lists. Curly brackets are
for hashes.
In any case, wouldn't it be smarter to organize your data differently?
I.e.:
%parent = ( 'Joe' = { 'address' = '21A', children = ['Dick','Sally'] } );
To add another child to an existing parent you'd then say
push @{$parent{'Joe'}{'children'}}, 'Jane';
To add a new parent:
@{$parent{'Sven'}}{'address','children'} = ( '9b', ['Bjorn'] );
HTH,
Thomas
AW: Burnt Camel Club
Ian pcs...@gmail.com wrote: Keep it up and the hollier-than-though's will have the list to themselves eventually. What's holly got to do with it, though? ;-) SCNR, Thomas ;-) -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: CGI and persistent data (without Storable)
Steve Bertrand st...@ibctech.ca asked: I'm writing a web interface using CGI::Application for a project that houses numerous methods within a dozen modules. One particular process displays a template to the user with passed in data, and then has four more steps before completing. The result of this procedure will be the modification of an elaborate data structure. The data structure may need to be modified along the way. Given that I can get through the web GUI portion of the process with just a couple of params, I'd like to find a way to retain the entire data structure without having to re-instantiate it (which requires rebuilding numerous objects etc), or pass each variable within it as a param on each CGI invocation. Can I, and is it plausible to create a cyclic ref redundancy of the data structure, store the memory location in a variable, pass the variable data as a param, and then recreate the data based on the variable that contains the memory location at the end of the entire CGI process? Is exploiting Perl's garbage collection like this possible, and ok to do? I'd like to be able to 'carry' the data structure without having to 'store' it to disk, if possible If you're using standard Perl CGI, a new interpreter is spawned for each of your requests. At the end of each request, the interpreter exists, and it takes any uncollected garbage with it. The next Perl process you start will get a completely new, empty, pristine memory space without any traces of previous use. So you can't store store data in memory between invocations that way. The easiest way to have persistent data across invocations is having a persistent Perl process and session handling. With CGI, this means using Apache and mod_perl and possibly a toolkit/framework/whatchamaycallit like Embperl on top. Although I have not used it yet personally, I would assume that the jifty framework is up to the task, too. If you can't use mod_perl or a stand-alone jifty server and if you have a Unix system, http://search.cpan.org/~samtregar/IPC-SharedCache-1.3/SharedCache.pm might be useful. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: How to pass info to a CGI program without using a form?
Disclaimer: I haven't written Perl or a major book on it so this answer is
strictly IMHO, OTTOH and of course YMMV ;-P
boll b...@sonic.net asked:
I would like to use this program in several places to display images
from other directories, so that one URL might display a random image
from the 'vegetables' directory, and a different URL would call the
same program but display an image from the 'fruits' directory.
You can tack on so-called GET parameters to an URL by adding pairs of
?key1=value1 [ key2=value2 ... [ keyn=valuen ] ]
Keys and values have to use a special encoding scheme for certain
special characters, see for example
http://en.wikipedia.org/wiki/Percent-encoding
In your code, you can query these parameters using the param() method of
CGI.pm, like this:
my $q = new CGI;
my $key1 = $q-param('key1');
Keep in mind that people might call your script without a parameter or that
they might try to hand-craft a value in order to exploit your code, so always
validate your input and always provide a sane default value.
For example if you had a parameter like image category, you'd probably only
want to allow numbers and lower case letters:
# make sure that your CGI parameter is clean
my( $img_category ) = ( $q-param('category') =~ m/^([a-z0-9]+)$/ );
# default for bad/missing parameter
$img_category ||= 'flowers';
Selecting the image based on a given category is left as an exercise for the
reader. Hint: you might want to extend the format of the image file list to
include a category column.
HTH,
Thomas
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AW: Trying to remove text in inverted commas.
Hello Gregory, Gregory Machin gregory.mac...@gmail.com asked: I'm writing a script to import logs into a Mysql .. My Perl is rusty and I'm battling with a convention on the one column. I need to remove the text in inverted commas Prashil 106 so that just the number 106 remains.. I have been trying the following regex s/(\([^]+)\\s)//g but it doesn't seem to work. It's always helpful if we can see several lines of sample input aswell as the output you wish to achieve so that we can understand your problem better. If your code doesn't work, please post the relevant portion of it. The RE you quoted will match a substring consisting of a double quote, followed by at least one character that is not a double quote, followed by another double quote and finally a whitespace (blank, tab) character. The match will be removed sicne you replace it with an empty string. Due to the modifier /g it will do that to multiple instances of the match in one line.
AW: WELCOME to beginners@perl.org
Ajay Kumar aku...@securities.com asked: Gesendet: Freitag, 21. August 2009 12:23 An: beginners@perl.org Betreff: RE: WELCOME to beginners@perl.org Hi All I have great issues 1) perl -e '$a=0.123451005;$a=sprintf(%.8f,$a);print=$a\n;' Output=0.12345101 2) perl -e '$a=5.123451005;$a=sprintf(%.8f,$a);print=$a\n;' Output=5.12345100 Here 1 one ging correct result but the second one wrong result For second one result should be 5.12345101 but it is giving 5.12345100 May I know why it behabe So See the first question in the Data: Number section of http://perldoc.perl.org/perlfaq4.html For the gritty details, see the article http://en.wikipedia.org/wiki/Floating_point and especially its setion representable numbers at Wikipedia. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: fast installing modules
Jenn G. practicalp...@gmail.com asked: We have a project which has 30+ perl/modperl modules. Installing those modules by hand on each host is wasting time. So can we just copy the directory /usr/lib/perl5/ from the already installed host to any other not installed hosts? We use Linux OS, perl version is 5.8.8. That sounds like a recipe for disaster. Some possibilities: 1) You could use the autobundle function of CPAN.pm: perl -MCPAN -e autobundle This will create a listing of all currently installed modules on your system. You can then copy that list to your target systems and do perl -MCPAN -e 'install Bundle::Snapshot_snapshot_date_time which will do a more or less automated install of all missing modules. Pro: Should work fine for different architectures and OS releases/patchlevels Con: Slow. Might install a different Perl version on your system (ouch!), unless you edit the packlist afterwards. That would require you knowing what you need module-wise, though. 2) If your project is a single executable and the target systems are all of the same architecture, you could use PAR to generate a standalone application. Pro: Easy to deploy - just copy one file. Doesn't mess with the distro's Perl installation. Con: Not so easy to create if you have external dependencies to certain libs etc. PAR archive is architecture/OS release specific. 3) If you have multiple executables, then Roll your own Perl might be an option. Create a package subdirectory under /opt and install your own Perl in /opt/yourpackage/bin with the the corresponding modules in /opt/yourpackage/lib. To distribute, simply copy /opt/yourpackage to the target systems. Pro: Doesn't mess with the distro's Perl installation. Incremental update capability using rsync ;-) Con: executables have to be fixed to call the proper Perl interpreter. Package is architecture/OS release specific. 4) If you're using Debian or a distro derived from it, you could use dh-make-perl to package the required modules that are not available from the distro itself. For deployment, you'd need a simple installer script that would load the required modules from a repository or the packages that you've made. The deluxe version would be to package your application itself; listing the required packages as dependencies. Pro: Clean integration into the distro's package management. Dependencies can be detected and installed if necessary. Depending on how professional you want to get you can keep your own repository woth multiple package versions around. Ideally installation could be automated to a simple apt-get install xxx on the target system if you package your application and use repository for your packages. Con: Package management takes some time to learn. Can be tricky to set up for multiple architectures. Requires some effort to maintain the module packages. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: delete 20 000 records in oracle from perl
luke devon luke_de...@yahoo.com asked: Since i have more binary data to be deleted in the requested query , i have to use a external script/program to satisfy the deletion. So thats why i wanted to know , how can we implement multi threading for the situation. You said that CPU load is high when deleting the records, and yet you want to do multiple delete queries at once? That doesn't sound like a good idea to me ;-) Also, if a delete query on a single records takes two minutes, then it might be worth your while to investigate the causes. Is there an index on the key you're using to select rows to delete? Have you had a pro look at the database configuration? I seem to recall that unlike consumer DBMS like MySQL, Oracle requires frequent tuning to optimize performance. HTH, Thomas
AW: Having problems getting data back to STDOUT once I assign it to a file
Wagner, David --- Senior Programmer Analyst --- CFS david.wag...@fedex.com asked: I have looked at perldoc -f open and tried a number of things. The line should be last line is appearing in my audittrail file, but I never see the EndOfProg or Error in the auditrrail or on the screen. Try perldoc -f select: select FILEHANDLE select Returns the currently selected filehandle. If FILEHANDLE is supplied, sets the new current default filehandle for output. [...] That way you could re-select() a previously saved handle to STDOUT. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: How to implement ping script to monitor server up/down state in perl ?
Amit Saxena learn.tech...@gmail.com asked: I want a perl ping script (console based) to monitor server up/down state. Why re-invent the wheel when there's already stuff like mon (http://mon.wiki.kernel.org/index.php/Main_Page) or nagios (http://www.nagios.org/)? HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: How to implement ping script to monitor server up/down state in perl ?
Amit Saxena learn.tech...@gmail.com wrote: Hi Thomas, Thanks for the response. The client for which I am working will not allow any external utility / modules to be installed on their development / production environments. Moreover they want the solution implemented using Perl only. Actually, mon ist pure Perl, so it should fit the bill on that count. Depending on the OS/distro your customer is using, they might even be able to install a mon package from one of their trusted sources. Even if you're not going to use mon, it should provide you with a wealth of ideas on how to write monitoring code in Perl. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: bug in perl?
Octavian Rasnita orasn...@gmail.com asked: I have tried the following calculation with ActivePerl 5.10.0 build 1004 under Windows XP Pro: print 0.79 - 0.798; And it gave the following result: -0.00801 which is obviously wrong. No, it isn't. Welcome to the wonderful world of machine numbers. Please read perldoc -q number. It doesn't matter too much the reasons, but is there a better way for doing such math calculations in perl? If you're dealing with money, it's a common practice to work with cents and integers instead of using floating point numbers. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: bug in perl?
Paul Johnson p...@pjcj.net wrote: On Fri, Jul 17, 2009 at 12:26:58PM +0200, Thomas Bätzler wrote: Octavian Rasnita orasn...@gmail.com asked: I have tried the following calculation with ActivePerl 5.10.0 build 1004 under Windows XP Pro: print 0.79 - 0.798; And it gave the following result: -0.00801 which is obviously wrong. No, it isn't. Well ... yes, it is. Let's settle on the result isn't what you'd expect if you had no prior experience with machine numbers ;-) Cheers, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
AW: Time stamp in file name.
Meghanand Acharekar vasco.deb...@gmail.com asked: I am writing a perl script which creates a file (on Linux/UNIX) using system's date. e.g. log_2009-07-07.gz Here is the code I wrote. #!/usr/bin/perl -w use strict; # Prog for demostrating file name concatenations. $prefix=log; $suffix=.gz; my $prefix = 'log'; my $suffix = '.gz'; ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst)=localtime(time); my($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst)=localtime(time); # Time $middle=sprintf %4d-%02d-%02d \n,$year+1900,$mon+1,$mday; # note no \n here! my $middle=sprintf %4d-%02d-%02d,$year+1900,$mon+1,$mday; print My Date : $middle\n; $file_name=join(_,$prefix.$middle.$suffix); my $file_name=join(_, $prefix, $middle, $suffix ); print New File name : $file_name \n; __END__ HTH, Thomas
AW: Edit text file using perl script
Alpesh Naik naik.alp...@gmail.com asked: I am trying to edit the text file using perl script. i want to replace a particular text of file with new text. but the problem is that the new text appeared at end of file; How can i solve this problem, pls. help We can help you much better if we can actually see what you're doing, so please include sample code. A working pattern for modifying a file goes like this: 1. open old file or reading 2. open temporary file for writing 3. read a line from the old file 4. if the line matches your criteria, then modify the line 5. write the line to the temporary file 6. If you have not reached the end of the old file yet, continue at 3. 7. close the old file 8. close the temporary file 9. rename the old file to a temporary filename 10. rename the temporary file to the name of the old file 11. optionally, delete the old file It's not an in-place edit, but it works. If you need to do in-place edits, you should look at seek() and understand the constraints of doing an in-place edit. HTH, Thomas -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
