Example buffer:
Line 1 is my favourite line Line 2 is bad Line 3 is bad Line 1 is still my favourite line
How do I use regex to match the 2 sentences that contain "Line 1" ?
Please note that the number '1' is not known to me, Only thing that's known is that the multiple occurences have the same number.
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";
output
Line 1 is my favourite line
Line 1 is still my favourite line
\2 which is reference to ([0-9]+)). If you need something more complex, regex is probably not right tool for the job.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
Output:
Smartmatch is experimental at ./tst.pl line 16.
Line 1 occurred before.
Whilst the above code is good to pick up line numbers that have occurred, it doesn't tell you what those lines are. If you do want that feature, then try the following code:
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;
}
Output:
Line 1 is my favourite line
Line 1 is still my favourite line
