match a word and delete last line

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

Hi, I am trying to match the word (sample-text) and delete previous line if has a single word that might include (digit,_,-).

use strict;
use warnings;

my $filename = 'test1.txt';
open(my $fh, '<:encoding(UTF-8)', $filename)
  or die "Could not open file '$filename' $!";

my $line;
my $flag=1;
 while($line=<$fh>)
 {
     if($flag == 0)
     {
         print $line;
         next;
     }
     if($line=~/sample-text/)
     {
         $flag=0;
         print $line;
     }
}
[download]

Content of the test1.txt

 
Text_1
sample-text file Text_1
 matching the 1st line
 matching the last line
Text
text_1
text-2
sample-text file text-2
 matching the 1st line
 matching the last line
[download]

Expected output

 
sample-text file Text_1
 matching the 1st line
 matching the last line
text
text_1
sample-text file text-2
 matching the 1st line
 matching the last line
[download]

But it only removes the 1st line, and doesn't look for other lines. Please let me know.

Comment on match a word and delete last line Select or Download Code

Replies are listed 'Best First'.
Re: match a word and delete last line by tybalt89 (Monsignor) on May 23, 2017 at 13:40 UTC
`#!/usr/bin/perl # http://perlmonks.org/?node_id=1190966 use strict; use warnings; $_ = do { local $/; <DATA> }; s/^(\w+[-_]\d+)\n(?=.*\1\b)//gm; print; __DATA__ Text_1 sample-text file Text_1 matching the 1st line matching the last line Text text_1 text-2 sample-text file text-2 matching the 1st line matching the last line` [download]	[reply] [d/l]
Re^2: match a word and delete last line by ArifS (Beadle) on May 23, 2017 at 14:03 UTC
tybalt89, how do I modify to remove the previous line word if doesn't include (d,_,-) for example if only says Text. `sample-text file Text-1 matching the 1st line matching the last line text text_1 sample-text file text-2 matching the 1st line matching the last line text_1 text-2 text sample-text file text matching the 1st line matching the last line` [download] I need to remove the following ( text ) too- `..................... text_1 text-2 text sample-text file text matching the 1st line matching the last line` [download]	[reply] [d/l] [select]
Re^3: match a word and delete last line by tybalt89 (Monsignor) on May 23, 2017 at 14:17 UTC
Try this, but your question is a little unclear. Please give an exact input and output test case, not a partial one. `#!/usr/bin/perl # http://perlmonks.org/?node_id=1190966 use strict; use warnings; $_ = do { local $/; <DATA> }; s/^(\w+(?:[-_]\d+)?)\n(?=.*\1\b)//gm; print; __DATA__ Text_1 sample-text file Text_1 matching the 1st line matching the last line Text text_1 text-2 sample-text file text-2 matching the 1st line matching the last line text_1 text-2 text sample-text file text matching the 1st line matching the last line` [download]	[reply] [d/l]
Re^4: match a word and delete last line by ArifS (Beadle) on May 23, 2017 at 14:23 UTC
Re^2: match a word and delete last line by ArifS (Beadle) on May 23, 2017 at 13:45 UTC
That works. Thank you.	[reply]
Re: match a word and delete last line by hippo (Archbishop) on May 23, 2017 at 13:49 UTC
But it only removes the 1st line, and doesn't look for other lines. Please let me know. That's because once `$flag` is set to zero, it will always be zero. There is no place in your code where it can be reset to 1. You will have to re-think the fine detail of your algorithm.	[reply] [d/l]
Re: match a word and delete last line by BillKSmith (Monsignor) on May 23, 2017 at 22:59 UTC
Your task is trivial if you process the file backwards and then reverse the result. `use strict; use warnings; use File::ReadBackwards; my $INFILE = File::ReadBackwards->new( 'infile.txt' ) or die "Cannot open infile.txt\n$!"; open my $TMPFILE, '>', 'backward.txt'; while (defined( $_ = $INFILE->readline)) { print {$TMPFILE} $_; next if !/sample-text/; $INFILE->readline; } $INFILE->close; close $TMPFILE; my $BCKFILE = File::ReadBackwards->new( 'backward.txt' ); while (defined( my $line = $BCKFILE->readline)) { print $line; } $BCKFILE->close; unlink 'backward.txt';` [download] Bill	[reply] [d/l]