bin/mytail-f.pl

   1 #!/usr/bin/perl
   2
   3 =pod
   4
   5 with help from perlfaq5
   6
   7 Displays the whole file with leading line number and timestamp and
   8 switches to 'tail -f' mode when the end is reached.
   9
  10 =cut
  11
  12 use Time::HiRes qw(time sleep);
  13 my $curpos = 0;
  14 my $line;
  15 my $i = 0;
  16 my $file = shift or die "Usage";
  17 open GWFILE, $file or die "Could not open '$file': $!";
  18 my $lines;
  19 while (<GWFILE>) {
  20   $lines = $.;
  21 }
  22 close GWFILE;
  23 open GWFILE, $file or die "Could not open '$file': $!";
  24 for (;;) {
  25   for ($curpos = tell(GWFILE); $line = <GWFILE>; $curpos = tell(GWFILE)) {
  26     if (++$i > $lines - 10) {
  27       my @time = localtime;
  28       my $localtime = sprintf "%02d:%02d:%02d", @time[2,1,0];
  29       my $fractime = time;
  30       $fractime =~ s/\d+\.//;
  31       $fractime .= "0000";
  32       printf "%5d %s.%s %s", $i, $localtime, substr($fractime,0,4), $line;
  33     }
  34   }
  35   sleep 2;
  36   seek(GWFILE, $curpos, 0);  # seek to where we had been
  37 }