skipline

   1 #!/usr/bin/env perl
   2
   3 # skipline
   4 # File ID: dcd11fb0-5d43-11df-8525-90e6ba3022ac
   5 # Only prints every n'th line from stdin
   6
   7 use warnings;
   8
   9 defined($ARGV[0]) || die("\nSyntax: $0 number_of_lines_to_skip [file [...]]\n\n");
  10
  11 my $Skip = $ARGV[0];
  12 shift;
  13
  14 ($Skip =~ /[^0-9]/) && die("$Skip: Invalid character in number");
  15 $Skip || die("Number has to be greater than zero");
  16
  17 my $Count = 0;
  18
  19 while(<>) {
  20         ($Count++ % $Skip) || print;
  21 }