Re: File Parsing Question
William Black wrote:
Hello,
I'm trying to figure out how to read multiple lines from a file at once for
parsing. For example,, If the file contained the following:
input file
Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
I want to read in lines 1-4 for processing then during the next iteration
read lines 5-8. Could someone give me a could starting place?
I know of no other way than the hard way.
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
while( ! eof DATA ){
my @lines = ();
for my $i ( 1 .. 4 ){
my $line = ;
push @lines, $line;
}
# process @lines
print Dumper [EMAIL PROTECTED];
}
__END__
line 1
line 2
line 3
line 4
line 5
line 6
line 7
line 8
line 9
--
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re: File Parsing Question
Hello, I'm trying to figure out how to read multiple lines from a file at once for parsing. For example,, If the file contained the following: input file Line 1 Line 2 Line 3 Line 4 Line 5 Line 6 Line 7 Line 8 I want to read in lines 1-4 for processing then during the next iteration read lines 5-8. Could someone give me a could starting place? -- William Black [EMAIL PROTECTED]
Re: [beginner] file parsing question
- Original Message -
From: Stout, Joel R <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, April 24, 2001 10:20 PM
Subject: [beginner] file parsing question
> Sorry so lengthy but here goes:
>
> I am a Perl newbie and trying to parse a file. Depending on the tags in
the
> data I want to parse each line a different way. I built the following
> program to test my process.
>
> use strict;
> my (@lines, $testln, @REFln);
What is @lines for? Is doesnt seem to be used.
And @REFln could be declared inside sub parseREF; where $testln is better
declared locally in sub testType.
It might also be more efficient to read the file one time and then process
it
try this:
#!perl
my @lines = (<>);
foreach $line (@lines) {
chomp $line;
my ($element1, $element2, $element3) = split (/\*/, $line, 3);
if ($element1 eq 'REF' && !($element2 eq 'SN')) {
print "Not a Shipment Number, $element1 type $line.\n";
} else {
print "I found a $element1 line: $line\n";
}
}
>
> while (<>) {
> chomp;
> testType ($_);
> }
>
> sub testType {
> $testln = $_[0];
> if (/^REF/) {
> print "I found a REF line: $testln\n";
> parseRef ($testln);
> } elsif (/^NTE/) {
> print "I found a NTE line: $testln\n";
> }
> }
>
> sub parseREF {
> print "Parsing line: $_[0]\n";
>
> @REFln = split (/\*/, $_[0]);
>
> print "Element 1) $REFln[0] ";
> print " 2) $REFln[1] ";
> print " 3) $REFln[2]\n";
>
> if ($REFln[1] = "SN") {
> print "$REFln[1]: $REFln[2]\n";
> } else {
> print "Not a Shipment Number, $REFln[1] type line.\n";
> }
> }
>
> Based on the input:
> CUR**USD
> REF*SN*0108106
> REF*PO*cn190108106
> REF*BL*cn190108106
> REF*PS*JessupPA
>
> I expected to see "SN: 0108106" (which I did) but I didn't expect to see
> "SN: cn190108106" and "SN: cn190108106", "SN: JessupPA".
> I expected to see "Not a Shipment Number, PO/BL/PS type line." for those.
> It almost seems like $REFln[1] is not being refreshed each time parseREF
> happens.
>
> I have written this same program in VB but I'm trying to do my parsing in
> Perl now . To tell you the truth I really don't have a clue why this
> doesn't work, so any help is much appreciated.
>
> Joel
>
Re: [beginner] file parsing question
--- Timothy Kimball <[EMAIL PROTECTED]> wrote:
> Ah, yes, one of the most frustrating bugs in the world:
> : if ($REFln[1] = "SN") {
> This *assigns* the value "SN" to $REFln[1]. What you want to do is
> *test* it. String comparisons in Perl are done with "eq" (and numeric
> comparisons with "=="). So you want this:
> if ($REFln eq "SN") {
> You can avoid this by always writing comparisons with the constant
> (if there is one) on the left-hand side:
>
> if ("SN" eq $REFln)
>
> but I rarely see people actually do that.
People rarely do it, btu I *HIGHLY* recommend it.
This way, if you write
if ("SN" = $REFln) {
the compiler will shut down and warn you that you can't *do* that, and
you'll probably say "Oh! that should have been ==, or maybe eq"
It's just cleaner code. =o)
__
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Re: [beginner] file parsing question
On Tue, Apr 24, 2001 at 04:33:00PM -0400, Timothy Kimball wrote:
> You can avoid this by always writing comparisons with the constant
> (if there is one) on the left-hand side:
>
> if ("SN" eq $REFln)
>
> but I rarely see people actually do that.
I think that's because it feels so unnatural and looks so ugly ;-)
--
Paul Johnson - [EMAIL PROTECTED]
http://www.pjcj.net
Re: [beginner] file parsing question
Hi Joel,
Did you type this in by hand? :)
> parseRef ($testln);
> sub parseREF {
You would want to change one of those! Anyways..
Your problem is in this line:
> if ($REFln[1] = "SN") {
= is for assignments. You want this to be:
if ($REFln[1] eq "SN") {
To learn more about perl operators like eq, =, and == (which is for numeric
comparisons, while eq is for strings) read the perlop manual page.
Cheers,
Kevin
On Tue, Apr 24, 2001 at 08:20:59PM -, Stout, Joel R ([EMAIL PROTECTED])
spew-ed forth:
> Sorry so lengthy but here goes:
>
> I am a Perl newbie and trying to parse a file. Depending on the tags in the
> data I want to parse each line a different way. I built the following
> program to test my process.
>
> use strict;
> my (@lines, $testln, @REFln);
>
> while (<>) {
> chomp;
> testType ($_);
> }
>
> sub testType {
> $testln = $_[0];
> if (/^REF/) {
> print "I found a REF line: $testln\n";
> parseRef ($testln);
> } elsif (/^NTE/) {
> print "I found a NTE line: $testln\n";
> }
> }
>
> sub parseREF {
> print "Parsing line: $_[0]\n";
>
> @REFln = split (/\*/, $_[0]);
>
> print "Element 1) $REFln[0] ";
> print " 2) $REFln[1] ";
> print " 3) $REFln[2]\n";
>
> if ($REFln[1] = "SN") {
> print "$REFln[1]: $REFln[2]\n";
> } else {
> print "Not a Shipment Number, $REFln[1] type line.\n";
> }
> }
>
> Based on the input:
> CUR**USD
> REF*SN*0108106
> REF*PO*cn190108106
> REF*BL*cn190108106
> REF*PS*JessupPA
>
> I expected to see "SN: 0108106" (which I did) but I didn't expect to see
> "SN: cn190108106" and "SN: cn190108106", "SN: JessupPA".
> I expected to see "Not a Shipment Number, PO/BL/PS type line." for those.
> It almost seems like $REFln[1] is not being refreshed each time parseREF
> happens.
>
> I have written this same program in VB but I'm trying to do my parsing in
> Perl now . To tell you the truth I really don't have a clue why this
> doesn't work, so any help is much appreciated.
>
> Joel
>
Writing CGI Applications with Perl - http://perlcgi-book.com
--
Nuclear explosions under the Nevada desert? What the f*ck are we testing for?
We already know the sh*t blows up.
-- Frank Zappa
Re: [beginner] file parsing question
Ah, yes, one of the most frustrating bugs in the world:
: if ($REFln[1] = "SN") {
This *assigns* the value "SN" to $REFln[1]. What you want to do is
*test* it. String comparisons in Perl are done with "eq" (and numeric
comparisons with "=="). So you want this:
if ($REFln eq "SN") {
You can avoid this by always writing comparisons with the constant
(if there is one) on the left-hand side:
if ("SN" eq $REFln)
but I rarely see people actually do that.
--
Tim Kimball · ACDSD / MAST¦
Space Telescope Science Institute ¦ We are here on Earth to do good to others.
3700 San Martin Drive ¦ What the others are here for, I don't know.
Baltimore MD 21218 USA¦ -- W.H. Auden
[beginner] file parsing question
Sorry so lengthy but here goes:
I am a Perl newbie and trying to parse a file. Depending on the tags in the
data I want to parse each line a different way. I built the following
program to test my process.
use strict;
my (@lines, $testln, @REFln);
while (<>) {
chomp;
testType ($_);
}
sub testType {
$testln = $_[0];
if (/^REF/) {
print "I found a REF line: $testln\n";
parseRef ($testln);
} elsif (/^NTE/) {
print "I found a NTE line: $testln\n";
}
}
sub parseREF {
print "Parsing line: $_[0]\n";
@REFln = split (/\*/, $_[0]);
print "Element 1) $REFln[0] ";
print " 2) $REFln[1] ";
print " 3) $REFln[2]\n";
if ($REFln[1] = "SN") {
print "$REFln[1]: $REFln[2]\n";
} else {
print "Not a Shipment Number, $REFln[1] type line.\n";
}
}
Based on the input:
CUR**USD
REF*SN*0108106
REF*PO*cn190108106
REF*BL*cn190108106
REF*PS*JessupPA
I expected to see "SN: 0108106" (which I did) but I didn't expect to see
"SN: cn190108106" and "SN: cn190108106", "SN: JessupPA".
I expected to see "Not a Shipment Number, PO/BL/PS type line." for those.
It almost seems like $REFln[1] is not being refreshed each time parseREF
happens.
I have written this same program in VB but I'm trying to do my parsing in
Perl now . To tell you the truth I really don't have a clue why this
doesn't work, so any help is much appreciated.
Joel
