This sounds like a good job for Tie::File. (the following is untested.)

use strict;
use warnings;

use Tie::File;

my @array;
tie @array, 'Tie::File', 'filename.txt' or die $!;

foreach ( 0 .. $#array ) {
    if( $array[$_] =~ /word/ ) {
        $#array = ( $_ < $#array ) ? $_ + 1 : $_;
        last;
    }
}

untie @array;
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This works by iterating over the array tied to the file. When 'word' is found, the array is resized (by setting $#array to a smaller value). An extra check is done to ensure that if 'word' is found on the last line of the array we're not resizing the array larger than it previously was. The one inefficiency here is that behind the scenes Tie::File must learn how many lines there are in the array, and that means scanning through the file internally first. In practice it doesn't seem to slow things down noticably, but I suppose for super large files it could.

I often overlook Tie::File, thinking of it as mostly a novelty; not really something you would think of actually using. But I shouldn't think of it that way; it works, it's fast, and it makes some simple tasks even simpler.

my @lines;
open FILE, "<", "foo.txt";
while( <FILE> ){
  push @lines, $_;
  next unless /\byourWord\b/;
  <FILE> for 1 .. 5;
}
close FILE;
open FILE, ">", "foo.txt";
print FILE, @lines;
close FILE;
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my @lines;
open FILE, "<", "foo.txt";
while( <FILE> ){
  push @lines, $_;
  last if /\byourWord\b/;
}
close FILE;
open FILE, ">", "foo.txt";
print FILE, @lines;
close FILE;
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If the files aren't huge, or the word appears fairly early (a few hundred MB) in the file, then you can do this with a "one-liner" (wrapped for viewing; adjust quoting to your OS needs):

perl -e"BEGIN{$/=qq[the word or phrase]}" 
-ne"$n=tell ARGV; close ARGV; truncate $ARGV, $n" path\to\the\file
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Here's another one-liner that doesn't use a begin block:

perl -ni.bak -e "print; /word/ && last;" file.txt
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When the thought came to me, I was surprised at how simple the solution turned out to be.




Dave

That doesn't quite match the OPs stated requirements in that it will preserve the entire 'line', (which could be the entire file if this was a binary file), containing the keyword rather than truncating immediately after the keyword.

Has the advantage that it does matter how big the file (assuming non-binary), or how far into the file the truncation point is.

Has the disadvantage that it will consume more disc space rather than reducing it--if that was the original intent.

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

You can, but these simpler tasks are easier to do with an editor unless the file is very large:

ed file <<<$'/\<word\>/+,$d\nw'
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Update: Sure, you can do it with truncate too, like

perl -we 'open $F, "+<", $ARGV[0] or die; while (<$F>) { /\bword\b/ an
+d truncate $F, tell $F; }' file
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Using an external grep program might also be possible, but beware that this command below truncates before the line containing the word. (I only include it because this is the first use I've found for the bash <> redirection operator. perl -we 'length($n = `grep -wbm1 word`) and truncate STDIN, $n;' <>file

Hi everyone, WOW..!! I got so many replies.....I am trying to run the suggestions you gave...Now the problem I face is that...I am grepping an large xml file....(I dont have any hassles with memory ..) ..;-].....I have to grep for a word in the tail end of the file and remove the line below that word. thank u kindly,