Question

缓冲区示例：

Line 1 is my favourite line
Line 2 is bad
Line 3 is bad
Line 1 is still my favourite line

如何使用正则表达式匹配包含“第1行”的2个句子？

请注意，我不知道数字'1'，只知道多个出现的数字相同。

Answer 1

my $s = q{Line 1 is my favourite line
Line 2 is bad
Line 3 is bad
Line 1 is still my favourite line
};

my ($l1, undef, $l2) = $s =~ /(Line \s* ([0-9]+) .*) [\w\W]*? (Line \s* \2 .*)/x;
print "$l1\n$l2\n";

输出

Line 1 is my favourite line
Line 1 is still my favourite line

Answer 2

use 5.14.0; #including features 'say' and smart match (~~)
use warnings;


my @lines = (); #lines that occurred

while (<DATA>){
    my $line = /^(Line\s*+\d+\b)/ ? $1 : ''; #\b to avoid '2' matches '22'
    $line ~~  @lines and do {say "$line occurred before."; next;}; 
    push @lines, $line;
}


__DATA__
Line 1 is my favourite line
Line 2 is bad
Line 3 is bad
Line 1 is still my favourite line
Line 22 is bad

输出：

Smartmatch is experimental at ./tst.pl line 16.
Line 1 occurred before.

虽然上面的代码可以很好地获取已发生的行号，但它并不能告诉您这些行是什么。如果您确实需要该功能，请尝试以下代码：

my @lines = ();

while (<DATA>){
    my $line = /^(Line\s*+\d+\b)/ ? $1 : ''; #\b to avoid '2' matches '22'
    next unless $line;
    push @lines, $_;
    my @occurred = grep {/$line/} @lines;
    @occurred > 1 and print for @occurred;
}

输出：

Line 1 is my favourite line
Line 1 is still my favourite line

在perl中使用正则表达式多次匹配特定的未知

2 个答案: