Regex 正则表达式匹配不会在perl中生成输出

我有一个如下的测试文件：

t # 3-0, 1
v 0 0
v 1 19
v 2 2
u 0 1 2
u 0 2 2
u 1 2 2
t # 3-1, 1
v 0 0
v 1 15
v 2 2
u 0 1 2
u 0 2 2
u 1 2 2
t # 3-2, 1
v 0 0
v 1 17
v 2 2
u 0 1 2
u 0 2 2
u 1 2 2
t # 3-3, 1
v 0 0
v 1 18
v 2 7
u 0 1 2
u 0 2 2
u 1 2 2

我编写了以下代码以匹配事务的最后三行（每个事务以

t#

开头）

---

请您尝试以下方法：

#!/usr/bin/perl -w

my $ref;
open(FH, shift) or die;
while (<FH>) {
    chop;
    if (/^t\s*#/) {            # if a new transaction starts
        $ref = [];             # then create a new reference to an array
        push(@refs, $ref);     # and memorize the reference
    }
    push(@$ref, $_);           # append the line to the current array
}
for $ref (@refs) {
    print(join(" " x 4, $ref->[0], $ref->[-3], $ref->[-2], $ref->[-1]), "\n");
}

---

一种方法：将事务的所有行保存在缓冲区中，当您到达一个新的事务id时，将前一行以及该缓冲区中的最后三行一起存储

use warnings;
use strict;
use feature 'say';

my (@transactions, @trans_lines, $tid);

while (<>) { 
    chomp;

    if (/^(t\s*#\s*[0-9,\s-]+)/) { 
        if (not $tid) {      
            $tid = $1;   # the very first one starts
            next;
        }

        # Store previous id and its last three lines, reset
        push @transactions, [ $tid, @trans_lines[-3..-1] ];
        $tid = $1; 
        @trans_lines = ()
    }   

    push @trans_lines, $_; 
}


say "@$_" for @transactions;

或者，更好的方法是使用更完整的用法消息调用例程，等等

---

使用词法文件句柄，

打开我的$fh，您的代码按原样为我提供以下输出：

t # 3-0, 1  u 0 1 2 u 0 2 2 u 1 2 2
t # 3-1, 1  u 0 1 2 u 0 2 2 u 1 2 2
t # 3-2, 1  u 0 1 2 u 0 2 2 u 1 2 2
t # 3-3, 1  u 0 1 2 u 0 2 2 u 1 2 2

看来问题出在你没给我们看的东西上。可能输入文件来自不同的系统，并且具有系统无法识别的行尾

嵌套的
while
循环和
if
条件使代码比需要的更复杂（因此更难维护）。您可以使用以下方法在一个循环中完成所有操作：

#!/usr/bin/perl

use strict;
use warnings;

my $input = shift @ARGV or die $!;

open (my $fh, '<', $input) or die $!;

my ($transaction_id, $edge_1, $edge_2, $edge_3);

while (<$fh>) {
  if (m/^(t\h*#\h*[0-9,\h-]+)/) {
    $transaction_id = $1;
  } elsif (m/^(u\h+[0]\h+[1]\h+[2])/) {
    $edge_1 = $1;
  } elsif (m/^(u\h+[0]\h+[2]\h+[2])/) {
    $edge_2 = $1;
  } elsif (m/^(u\h+[1]\h+[2]\h+[2])/) {
    $edge_3 = $1;
  }

  if ($transaction_id and $edge_1 and $edge_2 and $edge_3) {
    print "$transaction_id\t$edge_1\t$edge_2\t$edge_3\n";
    ($transaction_id, $edge_1, $edge_2, $edge_3) = (undef) x 4;
  }
}

#/usr/bin/perl
严格使用；
使用警告；
my$input=shift@ARGV或die$！；
打开（my$fh），定义正则表达式模式
$skip
，
$data
和
$tran
，遍历数据，组装事务行并在新事务开始时推入数组

use strict;
use warnings;
use feature 'say';

use Data::Dumper;

my $skip = qr/^v \d+ \d+/;
my $data = qr/^u \d+ \d+ \d+/;
my $tran = qr/^t # \d-\d, \d/;

my @array;
my $line = <DATA>;

chomp($line);

 while( <DATA> ) {
    next if /$skip/;
    chomp;
    $line .= '  ' . $_ if /$data/;
    if( /$tran/ ) {
        push @array, $line;
        $line = $_;
    }
}

push @array, $line;

say Dumper(\@array);

__DATA__
t # 3-0, 1
v 0 0
v 1 19
v 2 2
u 0 1 2
u 0 2 2
u 1 2 2
t # 3-1, 1
v 0 0
v 1 15
v 2 2
u 0 1 2
u 0 2 2
u 1 2 2
t # 3-2, 1
v 0 0
v 1 17
v 2 2
u 0 1 2
u 0 2 2
u 1 2 2
t # 3-3, 1
v 0 0
v 1 18
v 2 7
u 0 1 2
u 0 2 2
u 1 2 2

my $file = shift @ARGV  // die "Usage: $0 file\n";

t # 3-0, 1  u 0 1 2 u 0 2 2 u 1 2 2
t # 3-1, 1  u 0 1 2 u 0 2 2 u 1 2 2
t # 3-2, 1  u 0 1 2 u 0 2 2 u 1 2 2
t # 3-3, 1  u 0 1 2 u 0 2 2 u 1 2 2

#!/usr/bin/perl

use strict;
use warnings;

my $input = shift @ARGV or die $!;

open (my $fh, '<', $input) or die $!;

my ($transaction_id, $edge_1, $edge_2, $edge_3);

while (<$fh>) {
  if (m/^(t\h*#\h*[0-9,\h-]+)/) {
    $transaction_id = $1;
  } elsif (m/^(u\h+[0]\h+[1]\h+[2])/) {
    $edge_1 = $1;
  } elsif (m/^(u\h+[0]\h+[2]\h+[2])/) {
    $edge_2 = $1;
  } elsif (m/^(u\h+[1]\h+[2]\h+[2])/) {
    $edge_3 = $1;
  }

  if ($transaction_id and $edge_1 and $edge_2 and $edge_3) {
    print "$transaction_id\t$edge_1\t$edge_2\t$edge_3\n";
    ($transaction_id, $edge_1, $edge_2, $edge_3) = (undef) x 4;
  }
}

use strict;
use warnings;
use feature 'say';

use Data::Dumper;

my $skip = qr/^v \d+ \d+/;
my $data = qr/^u \d+ \d+ \d+/;
my $tran = qr/^t # \d-\d, \d/;

my @array;
my $line = <DATA>;

chomp($line);

 while( <DATA> ) {
    next if /$skip/;
    chomp;
    $line .= '  ' . $_ if /$data/;
    if( /$tran/ ) {
        push @array, $line;
        $line = $_;
    }
}

push @array, $line;

say Dumper(\@array);

__DATA__
t # 3-0, 1
v 0 0
v 1 19
v 2 2
u 0 1 2
u 0 2 2
u 1 2 2
t # 3-1, 1
v 0 0
v 1 15
v 2 2
u 0 1 2
u 0 2 2
u 1 2 2
t # 3-2, 1
v 0 0
v 1 17
v 2 2
u 0 1 2
u 0 2 2
u 1 2 2
t # 3-3, 1
v 0 0
v 1 18
v 2 7
u 0 1 2
u 0 2 2
u 1 2 2

$VAR1 = [
          't # 3-0, 1  u 0 1 2  u 0 2 2  u 1 2 2',
          't # 3-1, 1  u 0 1 2  u 0 2 2  u 1 2 2',
          't # 3-2, 1  u 0 1 2  u 0 2 2  u 1 2 2',
          't # 3-3, 1  u 0 1 2  u 0 2 2  u 1 2 2'
        ];