Archive of UserLand's first discussion group, started October 5, 1998.

tail -f in a web page

Author:Brent Simmons
Posted:11/5/1999; 3:30:35 PM
Topic:A question for Apache gurus
Msg #:12764 (In response to 12763)
Prev/Next:12763 / 12765

Question for Perl scripters:

I want a web page that allows me to view the last n lines of the Apache log. This web page would auto-refresh every 10 seconds or so. It would be kind of like tail -f in a web page -- but also kind of like the WebSTAR console, which is the point, now that www.scripting.com isn't running in WebSTAR anymore.

Anyway, my method for getting the last n lines from a log file seems inefficient, as it requires looping through the entire log file twice. Can this be improved on? I'm a total newbie Perl scripter.

Here's my script:

#!/usr/bin/perl -w


$lines = 0;
$filename = "/var/log/httpd/access_log";


#Count the number of lines


open (FILE, $filename) or die "Can't open filename '$filename': $!";
while (sysread FILE, $buffer, 4096) {
    $lines+= ($buffer =~ tr/n//);
}
close FILE;


print $lines;
print " lines. \n";


$currline = 0;
$lastlines = "";
$numlastlines = 10;


open (FILE, $filename) or die "Can't open filename '$filename': $!";


#Get the last 10 lines in a string.


while () {


    if ($currline == $lines) {
	last;
    }


    if ($currline >= ($lines - $numlastlines)) {
	$lastlines = $lastlines . $_;
    }


    $currline++;
}


close FILE;


print $lastlines;


print "\n";


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