Problem with grabing last ten lines. 1

ETbyrne · Mar 22, 2007

I'm having trouble printing the last ten lines from a text file to another text file. It works until it gets to the line 20 and I get this error...

Use of uninitialized value in string at e:\0\74\38\237038\user\240783\htdocs\mywebs\ETbyrne\cgi-bin\redalert\ten_newest_maps.pl line 20.

here's my script:

Code:

#!/usr/bin/perl
use warnings;
use strict;
use CGI qw(:standard);
use Fcntl qw(:flock :seek);

open(FILE, ">>./mywebs/ETbyrne/redalert/links.txt") or die "Can not open links.txt: $!";
seek(FILE,0,0);
my @file = <FILE>;
@file = reverse(@file);
close FILE;

open(FH, "+<./mywebs/ETbyrne/redalert/newmaps.txt") or die "Cannot open newportals.txt: $!";
flock(FH,LOCK_EX);
seek(FH,0,SEEK_SET);

truncate(FH,0);

seek(FH,0,SEEK_SET);
print FH "$file[$_]" for (0..9); # This is line 20 #
close (FH);

print "<html><head><title>Thank You</title></head>\n";
print "<body>\n";
print "Your Map was added. click <a href=\"index.shtml\">here</a> to go to the home page.<br>\n";
print "</body></html>\n";

Thanks for all help.

_______________________________________

You don't know me.

brigmar · Mar 22, 2007

I think perhaps you're overcooking with the file open/seeks/etc... and you seem to have the directions back-to-front.

Code:

#!/usr/bin/perl
use warnings;
use strict;
use CGI qw(:standard);
use Fcntl qw(:flock :seek);

open(FILE, "<links.txt") or die "Can not open links.txt: $!";
my @file = <FILE>;
@file = (reverse(@file))[0..9];
close FILE;

open(FH, ">newmaps.txt") or die "Cannot open newmaps.txt: $!";
print FH foreach @file;
close (FH);

print "<html><head><title>Thank You</title></head>\n";
print "<body>\n";
print "Your Map was added. click <a href=\"index.shtml\">here</a> to go to the home page.<br>\n";
print "</body></html>\n";

As I understand it, a process prior to this one appends each new map to links.txt, and you want the last 10 in reverse order (newest first).

Obviously, add the full paths in your open statements....

ETbyrne · Mar 22, 2007

Thanks, it works now, but I kept one of the locks in so that the file newmaps.txt doesn't get corrupted when two people run the script at once.

_______________________________________

You don't know me.

KevinADC · Mar 22, 2007

You might want to look into using Tie::File, you can read and write files almost exactly like you do with a perl array.

------------------------------------------
- Kevin, perl coder unexceptional! [wiggle]

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Problem with grabing last ten lines. 1

ETbyrne

Programmer

brigmar

Programmer

ETbyrne

Programmer

KevinADC

Technical User

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