delete lines between two patterns without deleting the pattern - bash

Question

i have a file like below
[NAMES]
biren
bikash
dibya
[MAIL]
biren_k
bikash123
dibya008
my output should be like below
[NAMES]
[MAIL]
i tried the below code just to remove the lines between NAMES and MAIL, but it did not work.
sed -n '/NAMES/{p; :a; N; /MAIL/ba; s/.*\n//}; p' input.txt
Can anyone help please... i would prefer perl code if any...
NOTE: like [NAMES] and [MAIL] , i have a lot of headers in my actual file. here i have just shown two headers. I have to replace the contents below the headers(not all, only selected headers which are at random line numbers) with new contents. but first i nedd to delete the contents below them. Thats why i need my output like this. Any suggestions please...

Answer 1

You can modify sed as
$ sed '/\[NAMES\]/, /\[MAIL\]/ {/^\[/p; d}' input
[NAMES]
[MAIL]
biren_k
bikash123
dibya008

Answer 2

Please try this may be helpful on your question:
%hashes = (
"[NAMES]" => "<br/>kumar<br/>avi<br/><br/>\n",
"[MAIL]" => "<br/>biren_k<br/>bikash123<br/>dibya008<br/>\n"
);
my #arr = <DATA>;
foreach my $snarr(#arr)
{
chomp($snarr);
push(#newarr, "$snarr\n$hashes{$snarr}"), if( $hashes{$snarr} );
}
print #newarr;
__DATA__
[NAMES]
biren
bikash
dibya
[MAIL]
biren_k
bikash123
dibya008

Answer 3

Just replace the lines between my #erase = qw[ and ]; with HEADERS you meant to empty out.
#!/usr/bin/env perl
use strict;
use warnings;
push #ARGV, 'file.txt';
# here list out the HEADERS
# which content you wanna erase
my #erase = qw[
NAMES
MAIL
];
my %dump;
my $header;
# build a hash from your file
while (<>) {
if (/^\[([^\]]+)\]$/) {
$header = $1;
$dump{$header} = "";
next;
}
$dump{$header} .= $_ if $header;
}
# replace the content
# with empty string
foreach (#erase) {
$dump{$_} = "";
}
# now print it back to <STDOUT>
foreach (sort keys %dump) {
print "[$_]\n$dump{$_}\n";
}

Answer 4

I found solution to my problem here:
my #name_var = ();
while (<STDIN>)
{
last if ($_ =~ /^\n/ );
push(#name_var, $_);
}
my #mail_add = ();
while (<STDIN>)
{
last if ($_ =~ /^\n/ );
push(#mail_add, $_);
}
open(my $var, "input.txt") || die("Input File not found");
open(my $out, ">temp.txt") || die("Temp File not created");
while($line = <$var>)
{
# print $line;
if( $line =~ /\[NAMES\]/)
{
print $out $line;
print $out $name_var;
while(($line = <$var>) && ($line !~ /^\n/))
{
}
}
if( $line =~ /\[MAIL\]/)
{
print $out $line;
print $out $mail_add;
while(($line = <$var>) && ($line !~ /^\n/))
{
}
}
print $tcf_out $line;
}
close($var);
close($out);
open($var1,">input.txt") || die("failed to open\n");
open($out1,"<temp.txt") || die("failed to open\n");
while($fl = <$out1>)
{
print $var1 $fl;
}
close($var1);
close($out1);
Thank you all. I got the solution from stack overflow, perlmonk and few more sites related to perl.