如何精确匹配两个空行 [英] How to match exactly two empty lines

问题描述

我对正则表达式有疑问.我有一个文件，我需要以一种可以区分其中某些特定文本块的方式来解析它.这些文本块由两条空行分隔(有些块由3或1空行分隔，但我恰好需要2).所以我有一段代码，这是我认为应该匹配的\s*$^\s*$/正则表达式，但事实并非如此. 怎么了?

I have a question about regular expressions. I have a file and I need to parse it in such a way that I could distinguish some specific blocks of text in it. These blocks of text are separated by two empty lines (there are blocks which are separated by 3 or 1 empty lines but I need exactly 2). So I have a piece of code and this is \s*$^\s*$/ regular expression I think should match, but it does not. What is wrong?

$filename="yu";
open($in,$filename);
open(OUT,">>out.text");
while($str=<$in>)
{
unless($str = /^\s*$^\s*$/){
print "yes";
print OUT $str;
}
}
close($in);
close(OUT);

干杯， 尤里娅

推荐答案

新答案

在排除了> 2个空行的问题之后，在这里睡个好觉是一个更好的方法，甚至不需要着嘴.

After having problems excluding >2 empty lines, and a good nights sleep here is a better method that doesn't even need to slurp.

#!/usr/bin/perl

use strict;
use warnings;    

my $file = 'yu';
my @blocks; #each element will be an arrayref, one per block
            #that referenced array will hold lines in that block

open(my $fh, '<', $file);

my $empty = 0;
my $block_num = 0;
while (my $line = <$fh>) {
  chomp($line);
  if ($line =~ /^\s*$/) {
    $empty++;
  } elsif ($empty == 2) { #not blank and exactly 2 previous blanks
    $block_num++; # move on to next block
    $empty = 0;
  } else {
    $empty = 0;
  }

  push @{ $blocks[$block_num] }, $line;
}

#write out each block to a new file
my $file_num = 1;
foreach my $block (@blocks) {
  open(my $out, '>', $file_num++ . ".txt");
  print $out join("\n", @$block);
}

实际上，除了以后存储和写入外，您还可以随便在每个块中写入一个文件:

In fact rather than store and write later, you could simply write to one file per block as you go:

#!/usr/bin/perl

use strict;
use warnings;

my $file = 'yu';

open(my $fh, '<', $file);

my $empty = 0;
my $block_num = 1;
open(OUT, '>', $block_num . '.txt');
while (my $line = <$fh>) {
  chomp($line);
  if ($line =~ /^\s*$/) {
    $empty++;
  } elsif ($empty == 2) { #not blank and exactly 2 previous blanks
    close(OUT); #just learned this line isn't necessary, perldoc -f close
    open(OUT, '>', ++$block_num . '.txt');
    $empty = 0;
  } else {
    $empty = 0;
  }

  print OUT "$line\n";
}

close(OUT);

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