Richard Fernandez wrote:
> There's a FAQ that deals with coding a "tail -f" if you're logfile is
> on the same box as the perl script.
> But what if you want to use rsh to tail a file remotely?
>
> Here's what I have:
> ------------------------------8<------------------------------
> ---------8<---
> --------------------------------
>
> #!/usr/bin/perl -w
> use strict;
> use Net::Rsh;
>
> my $host = shift or die "usage: my_rsh <hostname> <command>";
> my $cmd = shift or die "usage: my_rsh <hostname> <command>";
>
> my $session = Net::Rsh -> new();
>
> my @output = $session->rsh($host, '<local_user>',
> '<remote_user>', $cmd) or
> die;
>
> for (@output) {print;}
>
> ----------------8<----------------------------8<--------------
> --------------
> -----------8<----------------
>
> and here's my command line:
>
> $ sudo my_rsh.pl <hostname> "tail -f /u01/app/apache/logs/access_log"
>
> It seems that I never reach the print statement...
>
> I've tried things like:
>
> open(OUTPUT, $session->rsh($host, '<local_user>',
> '<remote_user>', $cmd) )
> or die;
> while (<OUTPUT>) {print;}
>
> but that doesn't work.
The call to Net::Rsh::rsh is going to wait for the remote command to exit,
and then return the output as an array of lines. But tail -f is never going
to exit, so you need a different approach.
Try a pipe open like this:
open RSH, "rsh hostname tail -f /u01/app/apache/logs/access_log |"
or die $!;
print while <RSH>;
close RSH or die $!;
The print loop will run forever, so you'll have to interrupt your script.
The remote process will end when it tries to write the next line (it'll get
a SIGPIPE), or when the TCP keepalive detects that the client is gone.
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