Re: Deleting last 10 lines of a file
Thanks a lot Shlomi and Thomas.
I will try with these methods.
On Tue, Mar 23, 2010 at 7:13 PM, Shlomi Fish shlo...@iglu.org.il wrote:
Hi Sheela,
On Tuesday 23 Mar 2010 15:06:24 sheela b wrote:
Hi All,
How to delete last 10 lines of a file using Perl one liner?
I used the following one liner to delete first 10 lines of a file,
perl -i.bak -ne 'print unless 1..10' test.txt
If it doesn't have to be a one-liner, you can do it efficiently using the
following script:
#!/usr/bin/perl
use strict;
use warnings;
use File::ReadBackwards;
use Getopt::Long;
my $count;
GetOptions(
n=i = \$count,
);
if (!defined($count))
{
die Please specify -n for the line count.;
}
my $filename = shift;
my $bw = File::ReadBackwards-new($filename)
or die Could not backwards-open '$filename' - $!;
foreach my $idx (1 .. $count)
{
$bw-readline();
}
my $wanted_len = $bw-tell();
$bw-close();
open my $truncate_fh, +, $filename
or die Could not truncate-open '$filename' - $!;
truncate($truncate_fh, $wanted_len);
close($truncate_fh);
If you still insist on it being a one-liner, see:
http://mail.perl.org.il/pipermail/perl/2005-August/007316.html
You can do it as a one liner in a much less elegant way by using a cyclical
queue, but I can't be bothered to implement it.
Regards,
Shlomi Fish
Regards
Sheela
--
-
Shlomi Fish http://www.shlomifish.org/
Parody on The Fountainhead - http://shlom.in/towtf
Deletionists delete Wikipedia articles that they consider lame.
Chuck Norris deletes deletionists whom he considers lame.
Please reply to list if it's a mailing list post - http://shlom.in/reply .
Deleting last 10 lines of a file
Hi All, How to delete last 10 lines of a file using Perl one liner? I used the following one liner to delete first 10 lines of a file, perl -i.bak -ne 'print unless 1..10' test.txt Regards Sheela
AW: Deleting last 10 lines of a file
sheela b sheela.b.2...@gmail.com asked:
How to delete last 10 lines of a file using Perl one liner?
I used the following one liner to delete first 10 lines of a file,
perl -i.bak -ne 'print unless 1..10' test.txt
OTTOH:
perl -i.bak -ne 'BEGIN { $b[9]= } print shift @b; push @b, $_'
test.txt
@b is the bucket chain of 10 initially empty strings. Inside the implied
while() loop, new text is added at the end of the chain while the head element
is pruned and then printed. The loop will terminate on eof(), leaving the last
10 lines of text in the array.
If you're dealing with small files, another option would be to slurp in the
file to an array, delete the last 10 items of the array and write the file back
out to disk.
HTH,
Thomas
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Re: Deleting last 10 lines of a file
Hi Sheela,
On Tuesday 23 Mar 2010 15:06:24 sheela b wrote:
Hi All,
How to delete last 10 lines of a file using Perl one liner?
I used the following one liner to delete first 10 lines of a file,
perl -i.bak -ne 'print unless 1..10' test.txt
If it doesn't have to be a one-liner, you can do it efficiently using the
following script:
#!/usr/bin/perl
use strict;
use warnings;
use File::ReadBackwards;
use Getopt::Long;
my $count;
GetOptions(
n=i = \$count,
);
if (!defined($count))
{
die Please specify -n for the line count.;
}
my $filename = shift;
my $bw = File::ReadBackwards-new($filename)
or die Could not backwards-open '$filename' - $!;
foreach my $idx (1 .. $count)
{
$bw-readline();
}
my $wanted_len = $bw-tell();
$bw-close();
open my $truncate_fh, +, $filename
or die Could not truncate-open '$filename' - $!;
truncate($truncate_fh, $wanted_len);
close($truncate_fh);
If you still insist on it being a one-liner, see:
http://mail.perl.org.il/pipermail/perl/2005-August/007316.html
You can do it as a one liner in a much less elegant way by using a cyclical
queue, but I can't be bothered to implement it.
Regards,
Shlomi Fish
Regards
Sheela
--
-
Shlomi Fish http://www.shlomifish.org/
Parody on The Fountainhead - http://shlom.in/towtf
Deletionists delete Wikipedia articles that they consider lame.
Chuck Norris deletes deletionists whom he considers lame.
Please reply to list if it's a mailing list post - http://shlom.in/reply .
--
To unsubscribe, e-mail: beginners-unsubscr...@perl.org
For additional commands, e-mail: beginners-h...@perl.org
http://learn.perl.org/
