CODEWITHSUNDEEP
linuxperlunixcommand-line
xpt
xpt

Reputation: 22994

Skip lines when "perl -n"

The -n argument causes Perl to place a loop around the program, which makes it iterate over filename arguments somewhat like sed -n or awk.

Now, is it possible to skip grab some of the forthcoming lines lines in advance in script using -n? 

#!/usr/bin/perl -wn

if (/my case/) {
  # Skip two lines
  <>; <>;
  # Do something with the line just read.
}

The above is not working for me. $_ is stuck at the same line/content.

Upvotes: 1

Views: 121

Answers (2)

ikegami
ikegami

Reputation: 385647

Another approach is to use a sliding window buffer.

perl -ne'
   push @buf, $_;
   next if @buf <= 3;
   shift(@buf);

   if ($buf[0] =~ /c/) {
      my $line1 = $buf[1];
      my $line2 = $buf[2];
      ...
   }
'

Upvotes: 1

choroba
choroba

Reputation: 241828

It works for me:

perl -wE 'say for 1..10' | perl -ne 'if (/2/) { <>; <>; print "!$_" } else { print }'
1
!2
5
6
7
8
9
10

If you want to process the next two lines, store them in variables.

$line1 = <>; $line2 = <>;

<> on its own doesn't populate $_ - only in the special case of while (<>).

Upvotes: 3

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