If you want an over complex solution you could try using
use IPC::Open3;
use IO::Select;
use IO::Handle;
i.e.
#!/usr/local/bin/perl -w
use Data::Dumper;
use File::Copy;
use IPC::Open3;
use IO::Select;
use IO::Handle;
use strict;
use vars qw(
$line $select
$read $write $error
);
( $select, $read, $error ) =
process_command('/usr/bin/tail -f tmp.dat');
process_tail($select);
close_handles( $read, $error );
sub process_command {
my ($command) = @_;
my ( $pid, $readbuff, $timeout, $s );
$timeout = 10;
$read = new IO::Handle;
$error = new IO::Handle;
$pid = open3( $write, $read, $error, $command );
#
# create selects
#
$s = IO::Select->new();
$s->add($read);
$s->add($error);
return ( $s, $read, $error ); }
sub process_tail {
my ($select) = shift;
my ( @ready, $handle, $timeout, $readbuff, $flag, $tapeloc, $newnum );
$flag = 0;
#
# get write handle
#
while ( $flag == 0 ) {
@ready = $select->can_read($timeout);
foreach $handle (@ready) {
sysread( $handle, $readbuff, 256 ); # 256 is the number of chars
to read.
if ( length($readbuff) == 0 ) {
$flag = 1;
}
}
#
# do something here
#
print "$readbuff\n";
}
sleep(1);
}
sub close_handles {
my ( $r, $e ) = @_;
$r->close();
$e->close();
}
Its not been tested so not sure if it will do what you require.
-----Original Message-----
From: Octavian Rasnita [mailto:[EMAIL PROTECTED]
Sent: 24 July 2007 10:45
To: Jeff Pang; beginners perl
Subject: Re: reading from a file
From: "Jeff Pang" <[EMAIL PROTECTED]>
>
> --- Octavian Rasnita <[EMAIL PROTECTED]> wrote:
>
>> Hi,
>>
>> I am trying to read from a log file which increase continuously
>> almost every second.
>
> You may try the Unix 'tail' command and pipe the result to your Perl
> program.Like:
>
> tail -f access_log|perl -e
> 'while(<>){handle_routine()}'
>
> handle_routine() is your routine for handling logfile lines.
>
>
I can do this, but in that case I don't know how to be sure that I don't
skip any line of the file.
The condition is to not skip any line and to not get the same line twice.
I tested the tail command in the command line using:
tail -n 1 /path/to/file
because I wanted to get only the last line of the file.
If I use that command for more times, sometimes the same last line is
printed for more times, but sometimes the tail command doesn't print
anything.
I don't know if the result of tail can be trusted...
Thank you.
Octavian
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