Any Idea why this code doesn't remove all the blank lines?

[Jack Wang]

This is the code I've written so far.

#!/usr/bin/perl
my $result = "";
while (<>){
if (/---START---/../--END\s---/){
$result.=$_;
}
}
$text="";
$result=~m/^---START---(.*)--END\s---$/s;
$text.=$1;
$text =~ s/\n+/\n/g;
print $text;

This is the text that it should handle (shortened, ........ represents
more data).

---START---

1342A 1O B10/B11
1003 1O B45/Z46
1094 1O F39/F40
1416 1O G37/G38
1007 1O Z33/A34
..........................

.............................
.............................
.....stuff here..........
.....................

4105 4L F31/F32
.......................
......................

--END ---


I want to extract the data betweeen ---START--- and --END ---,
removing any blanklines. However, the above mentioned program would
outputs everything correctly except it leaves a blank line at the top
and I can't figure out why. Thanks for any help!

 

[John W. Krahn]

This is the code I've written so far.

#!/usr/bin/perl

use warnings;
use strict;

my $result = "";
while (<>){
if (/---START---/../--END\s---/){

next unless /\S/;
next if /---START---/ || /--END\s---/;

$result.=$_;
}
}
$text="";
$result=~m/^---START---(.*)--END\s---$/s;
$text.=$1;
$text =~ s/\n+/\n/g;
print $text;

John

 

[xhoster]

$result=~m/^---START---(.*)--END\s---$/s;
$text.=$1;
$text =~ s/\n+/\n/g;
....

However, the above mentioned program would
outputs everything correctly except it leaves a blank line at the top
and I can't figure out why. Thanks for any help!

You get a blank line either when there are two \n in a row, or when
the string has a single \n at the beginning. Your regex captures one,
but not the other.

Either don't capture them in the first place:

$result=~m/^---START---\n*(.*)--END\s---$/s;

Or remove it particularly:

$text =~ s/\n+/\n/g;
$text =~ s/^\n+//;

Xho

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[Uri Guttman]

JWK> use warnings;
JWK> use strict;

JWK> next unless /\S/;
JWK> next if /---START---/ || /--END\s---/;

you can use the return value of .. to eliminate the redundancy of those
regexes:

if ( my $range_num = /---START---/ .. /--END\s---/ ) {

next if $range_num == 1 || $range_num =~ /e/i ;
}


i would even drop the block:

my $range_num = /---START---/ .. /--END\s---/ ) {
next unless $range_num ;
next if $range_num == 1 || $range_num =~ /e/i ;
next unless /\S/ ;

but my favorite way is so much faster and shorter (untested):

use File::Slurp ;

my $text = read_file( \*STDIN ) ;
while( my( $result ) = $text =~ m/^---START---(.+)--END\s---$/msg ) {

# do newline and other cleanup here

$result =~ tr/\n//s ;

print $result ;
}

can't get much simpler than that.

uri

 

[Martijn Lievaart]

I want to extract the data betweeen ---START--- and --END ---,
removing any blanklines. However, the above mentioned program would
outputs everything correctly except it leaves a blank line at the top
and I can't figure out why. Thanks for any help!

Because you ask it to?

Your problem can be shortened to:
$ perl -e '$t="\ntest\n\ntest\n"; $t=~ s/^\n+/\n/g; print "t=$t\n"'

This does exactly the same thing, it leaves the first empty line. Why?
Because you replace the newline there wit a newline.

Try:
$ perl -e '$t="\ntest\n\ntest\n"; $t=~ s/\n+/x/g; print "t=$t\n"'

And you'll see what I mean.

You probably want to add:
$text =~ s/^\n//;
to achieve what you want.

Some stylistic issues:

#!/usr/bin/perl

use strict;
use warnings;

my $result = "";
while (<>){
if (/---START---/../--END\s---/){
$result.=$_;
}
}

Indentation helps for readability.

$text="";
$result=~m/^---START---(.*)--END\s---$/s;
$text.=$1;

Useless use of concatenation, Change to:

$result=~m/^---START---(.*)--END\s---$/s;
my $text = $1;

$text =~ s/\n+/\n/g;
print $text;

HTH,
M4

 

[Mario D'Alessio]

Try this:

while(<>)
{
#
# Grab the lines between these two lines (exclusive)
#
my $sequence = /---START---/.../--END\s---/;
next unless $sequence > 1; # Excludes left-hand pattern
next if $sequence =~ /E0$/; # Excludes right-hand pattern

next if /^\s*$/; # Skip blank lines
print;
}