[30207] in Perl-Users-Digest
Perl-Users Digest, Issue: 1450 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue Apr 15 16:30:53 2008
Date: Tue, 15 Apr 2008 13:30:41 -0700 (PDT)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Tue, 15 Apr 2008 Volume: 11 Number: 1450
Today's topics:
Unpack - getting values directly into the correct varia PugetSoundSylvia@gmail.com
Re: Unpack - getting values directly into the correct v xhoster@gmail.com
Re: Unpack - getting values directly into the correct v <someone@example.com>
Re: Unpack - getting values directly into the correct v <1usa@llenroc.ude.invalid>
Re: Unpack - getting values directly into the correct v <someone@example.com>
Re: Unpack - getting values directly into the correct v <1usa@llenroc.ude.invalid>
Re: Unpack - getting values directly into the correct v <nospam-abuse@ilyaz.org>
Re: Unpack - getting values directly into the correct v <someone@example.com>
Re: Unpack - getting values directly into the correct v <hjp-usenet2@hjp.at>
Re: Unpack - getting values directly into the correct v <nobull67@gmail.com>
use modules OS dependent sledz@dresearch.de
Re: use modules OS dependent <noreply@gunnar.cc>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Thu, 10 Apr 2008 08:52:55 -0700 (PDT)
From: PugetSoundSylvia@gmail.com
Subject: Unpack - getting values directly into the correct variables
Message-Id: <a9c1aa0a-7f6f-4d7d-94e9-dc474b1ba039@t12g2000prg.googlegroups.com>
Hello all,
I'm just starting to get into perl, so please forgive me if I'm asking
something obvious.
I'm using the unpack function to parse through a fixed length file.
It's working well, but there's lots and lots of fields, and I'd like
to make the code more readable.
What I have now is this:
$LOGFILE = "text.log";
open(LOGFILE) or die("Could not open log file.");
# Define the record format for unpack function
$BaseBSPFileTemplate =
"A3" # RecordType Field 0
."A8" # SequenceNumber Field 1
."A2" # RecordTypeSuffix Field 2
."A6" # CreateDate Field 3
."A6" # TransactionNumber Field 4
."A15" # DataNumber Field 5
."A98" # UpdateDate Field 6
;
while (<LOGFILE>) {
@fields = unpack( $BaseBSPFileTemplate, $_ );
$RecordType = $fields[0];
$SequenceNumber = $fields[1];
$RecordTypeSuffix = $fields[2];
... and so forth ...
Is there a better way to do this - one where the unpack function
itself would automatically split it into the actual variables
($RecordType, $SequenceNumber, $RecordTypeSuffix, etc) - instead of me
having to have the section that has a bunch of rows like this:
$RecordType = $fields[0];
Thanks much for any advice!!
Sylvia
------------------------------
Date: 10 Apr 2008 16:02:53 GMT
From: xhoster@gmail.com
Subject: Re: Unpack - getting values directly into the correct variables
Message-Id: <20080410120254.889$3p@newsreader.com>
PugetSoundSylvia@gmail.com wrote:
>
> while (<LOGFILE>) {
>
> @fields = unpack( $BaseBSPFileTemplate, $_ );
>
> $RecordType = $fields[0];
> $SequenceNumber = $fields[1];
> $RecordTypeSuffix = $fields[2];
>
> ... and so forth ...
>
> Is there a better way to do this - one where the unpack function
> itself would automatically split it into the actual variables
> ($RecordType, $SequenceNumber, $RecordTypeSuffix, etc) - instead of me
> having to have the section that has a bunch of rows like this:
You can assign directly to a list of variables:
my ( $RecordType,
$SequenceNumber,
$RecordTypeSuffix,
# ....
) = unpack( $BaseBSPFileTemplate, $_ );
Xho
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this fact.
------------------------------
Date: Thu, 10 Apr 2008 17:48:46 GMT
From: "John W. Krahn" <someone@example.com>
Subject: Re: Unpack - getting values directly into the correct variables
Message-Id: <2qsLj.27618$pb5.11173@edtnps89>
PugetSoundSylvia@gmail.com wrote:
>
> I'm just starting to get into perl, so please forgive me if I'm asking
> something obvious.
>
> I'm using the unpack function to parse through a fixed length file.
> It's working well, but there's lots and lots of fields, and I'd like
> to make the code more readable.
I see that Xho has answered your unpack question but ...
> What I have now is this:
You should really have these two lines at the beginning of your program:
use warnings;
use strict;
> $LOGFILE = "text.log";
Which means that you have to declare this variable:
my $LOGFILE = 'text.log';
> open(LOGFILE) or die("Could not open log file.");
And you should really be using the three argument form of open(). As
well, you should include the $! variable in the error message so you
know why it failed:
open LOGFILE, '<', $LOGFILE or die "Could not open '$LOGFILE' $!";
John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall
------------------------------
Date: Thu, 10 Apr 2008 17:53:05 GMT
From: "A. Sinan Unur" <1usa@llenroc.ude.invalid>
Subject: Re: Unpack - getting values directly into the correct variables
Message-Id: <Xns9A7C8D3B1C134asu1cornelledu@127.0.0.1>
PugetSoundSylvia@gmail.com wrote in
news:a9c1aa0a-7f6f-4d7d-94e9-dc474b1ba039
@t12g2000prg.googlegroups.co
m:
> Hello all,
>
> I'm just starting to get into perl, so please forgive me if I'm
> asking something obvious.
>
> I'm using the unpack function to parse through a fixed length
> file. It's working well, but there's lots and lots of fields, and
> I'd like to make the code more readable.
>
> What I have now is this:
>
> $LOGFILE = "text.log";
> open(LOGFILE) or die("Could not open log file.");
>
> # Define the record format for unpack function
> $BaseBSPFileTemplate =
> "A3" # RecordType Field 0
> ."A8" # SequenceNumber Field 1
> ."A2" # RecordTypeSuffix Field 2
> ."A6" # CreateDate Field 3
> ."A6" # TransactionNumber Field 4
> ."A15" # DataNumber Field 5
> ."A98" # UpdateDate Field 6
> ;
>
> while (<LOGFILE>) {
>
> @fields = unpack( $BaseBSPFileTemplate, $_ );
>
> $RecordType = $fields[0];
> $SequenceNumber = $fields[1];
> $RecordTypeSuffix = $fields[2];
#!/usr/bin/perl
use strict;
use warnings;
my @fields = qw( RecordType SequenceNumber RecordTypeSuffix
CreateDate TransactionNumber DataNumber UpdateDate );
my %formats;
@formats{ @fields } = qw( A3 A8 A2 A6 A6 A15 A98 );
my $unpack_tmpl = join( '', @formats{ @fields } );
while( <DATA> ) {
last if /^\s+$/;
my %obs;
@obs{ @fields } = unpack $unpack_tmpl;
print "$_\t$obs{$_}\n" for @fields;
}
__END__
00011111111223333334444445555555555555556666666666666666666666666666
66666666666666666666666666666666666666666666666666666666666666666666
66
--
A. Sinan Unur <1usa@llenroc.ude.invalid>
(remove .invalid and reverse each component for email address)
comp.lang.perl.misc guidelines on the WWW:
http://www.rehabitation.com/clpmisc/
------------------------------
Date: Thu, 10 Apr 2008 18:47:44 GMT
From: "John W. Krahn" <someone@example.com>
Subject: Re: Unpack - getting values directly into the correct variables
Message-Id: <khtLj.27964$pb5.25660@edtnps89>
A. Sinan Unur wrote:
> PugetSoundSylvia@gmail.com wrote in
> news:a9c1aa0a-7f6f-4d7d-94e9-dc474b1ba039
> @t12g2000prg.googlegroups.co
> m:
>
>> Hello all,
>>
>> I'm just starting to get into perl, so please forgive me if I'm
>> asking something obvious.
>>
>> I'm using the unpack function to parse through a fixed length
>> file. It's working well, but there's lots and lots of fields, and
>> I'd like to make the code more readable.
>>
>> What I have now is this:
>>
>> $LOGFILE = "text.log";
>> open(LOGFILE) or die("Could not open log file.");
>>
>> # Define the record format for unpack function
>> $BaseBSPFileTemplate =
>> "A3" # RecordType Field 0
>> ."A8" # SequenceNumber Field 1
>> ."A2" # RecordTypeSuffix Field 2
>> ."A6" # CreateDate Field 3
>> ."A6" # TransactionNumber Field 4
>> ."A15" # DataNumber Field 5
>> ."A98" # UpdateDate Field 6
>> ;
>>
>> while (<LOGFILE>) {
>>
>> @fields = unpack( $BaseBSPFileTemplate, $_ );
>>
>> $RecordType = $fields[0];
>> $SequenceNumber = $fields[1];
>> $RecordTypeSuffix = $fields[2];
>
> #!/usr/bin/perl
>
> use strict;
> use warnings;
>
> my @fields = qw( RecordType SequenceNumber RecordTypeSuffix
> CreateDate TransactionNumber DataNumber UpdateDate );
>
> my %formats;
> @formats{ @fields } = qw( A3 A8 A2 A6 A6 A15 A98 );
>
> my $unpack_tmpl = join( '', @formats{ @fields } );
>
> while( <DATA> ) {
> last if /^\s+$/;
> my %obs;
> @obs{ @fields } = unpack $unpack_tmpl;
Don't forget the variable that you want to unpack:
@obs{ @fields } = unpack $unpack_tmpl, $_;
> print "$_\t$obs{$_}\n" for @fields;
>
> }
>
> __END__
> 00011111111223333334444445555555555555556666666666666666666666666666
> 66666666666666666666666666666666666666666666666666666666666666666666
> 66
John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall
------------------------------
Date: Thu, 10 Apr 2008 23:27:00 GMT
From: "A. Sinan Unur" <1usa@llenroc.ude.invalid>
Subject: Re: Unpack - getting values directly into the correct variables
Message-Id: <Xns9A7CC5D7D7751asu1cornelledu@127.0.0.1>
"John W. Krahn" <someone@example.com> wrote in news:khtLj.27964
$pb5.25660@edtnps89:
> A. Sinan Unur wrote:
...
>> @obs{ @fields } = unpack $unpack_tmpl;
>
> Don't forget the variable that you want to unpack:
>
> @obs{ @fields } = unpack $unpack_tmpl, $_;
I didn't ;-) From perldoc -f unpack:
unpack TEMPLATE,EXPR
unpack TEMPLATE
...
If EXPR is omitted, unpacks the $_ string.
Sinan
--
A. Sinan Unur <1usa@llenroc.ude.invalid>
(remove .invalid and reverse each component for email address)
comp.lang.perl.misc guidelines on the WWW:
http://www.rehabitation.com/clpmisc/
------------------------------
Date: Thu, 10 Apr 2008 23:50:31 +0000 (UTC)
From: Ilya Zakharevich <nospam-abuse@ilyaz.org>
Subject: Re: Unpack - getting values directly into the correct variables
Message-Id: <ftm947$1q6b$1@agate.berkeley.edu>
[A complimentary Cc of this posting was sent to
<PugetSoundSylvia@gmail.com>], who wrote in article <a9c1aa0a-7f6f-4d7d-94e9-dc474b1ba039@t12g2000prg.googlegroups.com>:
> $BaseBSPFileTemplate =
> "A3" # RecordType Field 0
> ."A8" # SequenceNumber Field 1
> ."A2" # RecordTypeSuffix Field 2
> ."A6" # CreateDate Field 3
> ."A6" # TransactionNumber Field 4
> ."A15" # DataNumber Field 5
> ."A98" # UpdateDate Field 6
> ;
>
> while (<LOGFILE>) {
>
> @fields = unpack( $BaseBSPFileTemplate, $_ );
>
> $RecordType = $fields[0];
> $SequenceNumber = $fields[1];
> $RecordTypeSuffix = $fields[2];
What a horror... Here is an example (Audio::FindChunks):
my $wav_header = <<EOH;
a4 # header: 'RIFF'
V # size: Size of what follows
a4 # type: 'WAVE'
a4 # type1: 'fmt ' subchunk
V # size1: Size of the rest of subchunk
v # format: 1 for pcm
v # channels: 2 stereo 1 mono
V # frequency
V # bytes_per_sec
v # bytes_per_sample
v # bits_per_sample_channel
a4 # type2: 'data' subchunk
V # sizedata: Size of the rest of subchunk
EOH
my @wav_fields = ($wav_header =~ /^\s*\w+\s*#\s*(\w+)/mg);
$wav_header =~ s/#.*//g; # For v5.005
...
@vals{@wav_fields} = unpack $wav_header, $in or ...
Hope this helps,
Ilya
------------------------------
Date: Fri, 11 Apr 2008 04:31:30 GMT
From: "John W. Krahn" <someone@example.com>
Subject: Re: Unpack - getting values directly into the correct variables
Message-Id: <CQBLj.58897$_v3.18045@edtnps90>
A. Sinan Unur wrote:
> "John W. Krahn" <someone@example.com> wrote in news:khtLj.27964
> $pb5.25660@edtnps89:
>
>> A. Sinan Unur wrote:
> ...
>
>>> @obs{ @fields } = unpack $unpack_tmpl;
>> Don't forget the variable that you want to unpack:
>>
>> @obs{ @fields } = unpack $unpack_tmpl, $_;
>
> I didn't ;-) From perldoc -f unpack:
>
> unpack TEMPLATE,EXPR
> unpack TEMPLATE
> ...
> If EXPR is omitted, unpacks the $_ string.
That must be new for 5.10 cause it doesn't work in 5.8.8
$ perl -le'
$_ = q[1234567890123456789012345678901234567890];
print for unpack q[a4 a7 a3];
'
Not enough arguments for unpack at -e line 3, near "q[a4 a7 a3];"
Execution of -e aborted due to compilation errors.
John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall
------------------------------
Date: Sat, 12 Apr 2008 11:49:09 +0200
From: "Peter J. Holzer" <hjp-usenet2@hjp.at>
Subject: Re: Unpack - getting values directly into the correct variables
Message-Id: <slrng011cp.uag.hjp-usenet2@hrunkner.hjp.at>
On 2008-04-10 23:50, Ilya Zakharevich <nospam-abuse@ilyaz.org> wrote:
><PugetSoundSylvia@gmail.com>], who wrote in article <a9c1aa0a-7f6f-4d7d-94e9-dc474b1ba039@t12g2000prg.googlegroups.com>:
>> $BaseBSPFileTemplate =
>> "A3" # RecordType Field 0
>> ."A8" # SequenceNumber Field 1
>> ."A2" # RecordTypeSuffix Field 2
>> ."A6" # CreateDate Field 3
>> ."A6" # TransactionNumber Field 4
>> ."A15" # DataNumber Field 5
>> ."A98" # UpdateDate Field 6
>> ;
>>
>> while (<LOGFILE>) {
>>
>> @fields = unpack( $BaseBSPFileTemplate, $_ );
>>
>> $RecordType = $fields[0];
>> $SequenceNumber = $fields[1];
>> $RecordTypeSuffix = $fields[2];
>
> What a horror...
You could have phrased that more politely :-).
Actually, I think that's pretty low on the horror-scale. Tedious and
redundant, yes, but I've seen much worse code.
> Here is an example (Audio::FindChunks):
>
> my $wav_header = <<EOH;
> a4 # header: 'RIFF'
> V # size: Size of what follows
> a4 # type: 'WAVE'
>
> a4 # type1: 'fmt ' subchunk
> V # size1: Size of the rest of subchunk
> v # format: 1 for pcm
> v # channels: 2 stereo 1 mono
> V # frequency
> V # bytes_per_sec
> v # bytes_per_sample
> v # bits_per_sample_channel
>
> a4 # type2: 'data' subchunk
> V # sizedata: Size of the rest of subchunk
> EOH
>
> my @wav_fields = ($wav_header =~ /^\s*\w+\s*#\s*(\w+)/mg);
>
> $wav_header =~ s/#.*//g; # For v5.005
> ...
> @vals{@wav_fields} = unpack $wav_header, $in or ...
Clever. Maybe a bit too clever for production code. At least I would add
a comment about the format (so that the next maintainer doesn't break
it) and why it works.
I'd use an array of arrays instead:
#!/usr/bin/perl
use warnings;
use strict;
my @BaseBSPFileFormat = (
["RecordType", "A3" ],
["SequenceNumber", "A8" ],
["RecordTypeSuffix", "A2" ],
["CreateDate", "A6" ],
["TransactionNumber", "A6" ],
["DataNumber", "A15" ],
["UpdateDate", "A98" ],
);
my $BaseBSPFileTemplate = join('', map $_->[1], @BaseBSPFileFormat);
my @BaseBSPFileFields = map $_->[0], @BaseBSPFileFormat;
while (<DATA>) {
my %fields;
@fields{@BaseBSPFileFields} = unpack( $BaseBSPFileTemplate, $_ );
for (@BaseBSPFileFields) {
print "$_: $fields{$_}\n";
}
print "\n"
}
__DATA__
111222222223344444455555566666666666666677777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777
111222222223344444455555566666666666666677777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777
hp
------------------------------
Date: Sat, 12 Apr 2008 03:03:41 -0700 (PDT)
From: Brian McCauley <nobull67@gmail.com>
Subject: Re: Unpack - getting values directly into the correct variables
Message-Id: <bfd91bfe-5ff0-4ce5-a677-187a521431f7@8g2000hsu.googlegroups.com>
On Apr 11, 5:31 am, "John W. Krahn" <some...@example.com> wrote:
> A. Sinan Unur wrote:
> > "John W. Krahn" <some...@example.com> wrote in news:khtLj.27964
> > unpack TEMPLATE,EXPR
> > unpack TEMPLATE
> > ...
> > If EXPR is omitted, unpacks the $_ string.
>
> That must be new for 5.10
And about $EXPLETIVE time! It's always bugged me that unpack didn't do
this.
------------------------------
Date: Mon, 14 Apr 2008 06:24:14 -0700 (PDT)
From: sledz@dresearch.de
Subject: use modules OS dependent
Message-Id: <c6676a33-ae66-4329-9b4c-f704244761e6@v26g2000prm.googlegroups.com>
I'm writing an perl script which should communicate over a serial
port. The script should be able to run in Linux and Win32
environments. In both environments exist modules to access the serial
port:
Win32::SerialPort (under Windows)
Device::SerialPort (else)
I know it is possible to detect the OS using Config::Config. But it
seems not possible to use different modules depending on this
information like this:
if ( $OS eq 'WINDOWS' ) {
use Win32::SerialPort qw( :PARAM :STAT );
} else {
use Device::SerialPort qw( :PARAM :STAT );
}
What's the right way to write such an OS dependent application?
Steffen
PS: Fup to comp.lang.perl.modules
------------------------------
Date: Mon, 14 Apr 2008 15:26:46 +0200
From: Gunnar Hjalmarsson <noreply@gunnar.cc>
Subject: Re: use modules OS dependent
Message-Id: <66h4g0F2kd0c4U2@mid.individual.net>
sledz@dresearch.de wrote:
> I'm writing an perl ...
I just answered your question in clpmodules. Please show some patience.
--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
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Subject: Digest Administrivia (Last modified: 6 Apr 01)
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------------------------------
End of Perl-Users Digest V11 Issue 1450
***************************************
