in reply to File::Tail on win32

THe following sample code should do it for you. You should omit the updateFile related code - that's just there to get the test file updated.

use strict;
use warnings;

my $logFileName = 'test.txt';
my $lastPos = 0;
my $endTime = time + 60;

while (time < $endTime)
  {
  next if ! -e $logFileName;
  next if $lastPos >= -s $logFileName;
  
  open inFile, '<', $logFileName;
  seek inFile, $lastPos, 0;
  print while <inFile>;
  $lastPos = tell inFile;
  close inFile;
  }
  continue
  {
  sleep (5);
  updateFile ();
  }

sub updateFile
{
open outFile, '>>', $logFileName;
print outFile 'Line added to file at ' . (join ', ', localtime) . "\n"
+;
close outFile;
}

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Printed:

Line added to file at 30, 16, 12, 30, 10, 105, 3, 333, 1
Line added to file at 35, 16, 12, 30, 10, 105, 3, 333, 1
Line added to file at 40, 16, 12, 30, 10, 105, 3, 333, 1
Line added to file at 45, 16, 12, 30, 10, 105, 3, 333, 1
Line added to file at 50, 16, 12, 30, 10, 105, 3, 333, 1
Line added to file at 55, 16, 12, 30, 10, 105, 3, 333, 1
Line added to file at 0, 17, 12, 30, 10, 105, 3, 333, 1
Line added to file at 5, 17, 12, 30, 10, 105, 3, 333, 1
Line added to file at 10, 17, 12, 30, 10, 105, 3, 333, 1
Line added to file at 15, 17, 12, 30, 10, 105, 3, 333, 1
Line added to file at 20, 17, 12, 30, 10, 105, 3, 333, 1

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DWIM is Perl's answer to Gödel

Replies are listed 'Best First'.
Re^2: File::Tail on win32
by perlAffen (Sexton) on Nov 30, 2005 at 00:47 UTC
    thanks, I'll hook it up to large file and try it.
[reply]
some more help
by perlAffen (Sexton) on Nov 30, 2005 at 01:44 UTC
    The script behaves strangely when the source file is removed and recreated.
    like so, test.txt is created by doing echo "" > test.txt
    run -> perl this.pl
    other window (ow) echo one >> test.txt
    one
    (ow) echo two >> test.txt
    two
    (ow) del /F test.txt
    (ow) echo uno > test.txt
    (ow) echo due >> test.txt
    (ow) echo tre >> test.txt
    re
    (ow) echo quattro >> test.txt
    quattro

    So it seems to hold on to the last cursor position and won't yield any output until that last postion is surpassed ?
    Also when you first run it, it outputs the entire file, is it possible to set $lastpos to its current EOF line ? ie Can it go to the bottom and wait for the next newline ?
    Also if I wanted to hand the output to a program, rather than print, how would I change
    print while <inFile>; ??
    Thanks !
[reply]

      This modified version may be closer to what you want:

      use strict;
use warnings;

my $logFileName = 'test.txt';
my $highWater = -1; # Signal first time through

while (1)
  {
  next if ! -e $logFileName;
  if ($highWater >= -s $logFileName)
    {
    $highWater = -s $logFileName; # Reset high water mark
    next;
    }
 
  open inFile, '<', $logFileName;
  seek inFile, $highWater, 0;
  #my @lines; # Uncomment to collate lines
  while (<inFile>)
    {
    print $_; # Replace with alternate code to handle output.
    #push @lines, $_; #Uncomment to collate lines
    }
  
  $highWater = tell inFile;
  close inFile;
  
  # Use @lines as required here to deal with added lines in one hit. e
+g.:
  #print @lines; #Uncomment to print collated lines
  }
  continue
  {
  sleep (5);
  }

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      DWIM is Perl's answer to Gödel
[reply]
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