Remove Lines from file

jreyesb has asked for the wisdom of the Perl Monks concerning the following question:

Hi everyone, Im newbie on perl and this site, i like it very much, most of all the top messages jejee like "Keep It Simple, Stupid" jajaja it kills me, ok, question. How can i delete the first 5 lines from a drive file, im doing this:

#!/usr/bin/perl

use strict;
use Tie::File;

my @parsedfiles;
my $n_files;

if (-e "last_processed.log") {
 tie @parsedfiles, 'Tie::File', "last_processed.log";
 n_files = @parsedfiles;

 if($n_files>=10) {
   for(my $i=0; $i<5; $i++) {
     delete $parsedfiles[$i];
   }
 }
 untie @parsedfiles;
[download]

But!!! it just remove the content of the lines and my file looks like:





6chale
7chale
8chale
9chale
10chale
11chale
12chale
[download]

Help please!!!! Thanks in advanced

Comment on Remove Lines from file Select or Download Code

Replies are listed 'Best First'.
Re: Remove Lines from file by Corion (Patriarch) on Jul 14, 2009 at 19:37 UTC
You want shift, or splice, not delete, which is for hashes. Actually, delete also is documented to work on arrays, but it sets the array element to `undef`, which Tie::File turns into the empty string, which doesn't help you.	[reply] [d/l]
Re^2: Remove Lines from file by ikegami (Patriarch) on Jul 14, 2009 at 19:45 UTC
Specifically, `for(my $i=0; $i<5; $i++) { delete $parsedfiles[$i]; }` [download] should be `splice(@parsedfiles, 0, 5);` [download]	[reply] [d/l] [select]
Re: Remove Lines from file by ikegami (Patriarch) on Jul 14, 2009 at 19:44 UTC
`perl -i.bak -ne'print if $. > 5' last_processed.log` [download]	[reply] [d/l]
Re: Remove Lines from file by johngg (Canon) on Jul 14, 2009 at 22:06 UTC
Another one-liner solution. `$ perl -ne 'BEGIN { <> for 1 .. 5 } print' file > newfile` [download] Cheers, JohnGG	[reply] [d/l]
Re: Remove Lines from file by Utilitarian (Vicar) on Jul 14, 2009 at 19:45 UTC
As a crude one liner `perl -e 'while (<>){if ($. > 5){print $_;}}' file >file.tmp;mv file.tmp file` To add sophistication print to a file handle, ie `use strict; use warnings; my ($FILE, $TEMP); open $FILE, "<", "file"; open $TEMP,">",file.tmp; while (<$FILE>){ if ($. > 5){ print $TEMP $_; } } close $FILE; close $TEMP; rename file.tmp, file;` [download]	[reply] [d/l] [select]
Re: Remove Lines from file by CountZero (Bishop) on Jul 14, 2009 at 19:45 UTC
Replace your `for`-loop by `shift @parsedfiles for (1..5);` [download] CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James	[reply] [d/l] [select]
Re: Remove Lines from file by ambrus (Abbot) on Jul 15, 2009 at 16:09 UTC
`sed -i 1,5d last_processed.log` [download]	[reply] [d/l]
Re: Remove Lines from file by johngg (Canon) on Jul 15, 2009 at 09:13 UTC
It seems you can use a `BEGIN {...}` block with the `-p` flag to skip lines as well but it might be too succinct for its own good. `$ perl -pe 'BEGIN { <> for 1 .. 5 }' file > newfile` [download] Cheers, JohnGG	[reply] [d/l] [select]