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From: PugetSoundSylvia on 10 Apr 2008 11:52
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
From: xhoster on 10 Apr 2008 12:02
PugetSoundSylvia(a)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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From: John W. Krahn on 10 Apr 2008 13:48
PugetSoundSylvia(a)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
From: A. Sinan Unur on 10 Apr 2008 13:53
PugetSoundSylvia(a)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(a)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/
From: John W. Krahn on 10 Apr 2008 14:47
A. Sinan Unur wrote:
> PugetSoundSylvia(a)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
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