Removing linefeeds from part of a file

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

I am somewhat stumped as to how to approach this problem.
Basiclly I have an ASCII text file that looks like this:

POSTNUM
12345
ENDPOSTNUM
DESCRIPTION
item 1
Item 2
item 3 long line
ENDDESCRIPTION
CONTACT
Bill Smith
ENDCONTACT
[download]

What I need to do is reformat just the DESCRIPTION section to remove the linefeeds in it so that it becomes:

POSTNUM
12345
ENDPOSTNUM
DESCRIPTION
item 1 Item 2 item 3 long line
ENDDESCRIPTION
CONTACT
Bill Smith
ENDCONTACT
[download]

Note that this shows a single record, there are close to 50 records like this in each file.
I have no idea how to approach this. Anyone who can point me a general direction for this would be a great help.

Comment on Removing linefeeds from part of a file Select or Download Code

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Re: Removing linefeeds from part of a file by Abigail (Deacon) on Jul 12, 2001 at 02:33 UTC
`{ local $\ = "\n"; while (<>) { chomp; if (/^ENDDESCRIPTION$/) { print "\n"; $\ = "\n"; } print; $\ = "" if /^DESCRIPTION$/; } }` [download] -- Abigail	[reply] [d/l]
Re: Removing linefeeds from part of a file by John M. Dlugosz (Monsignor) on Jul 12, 2001 at 01:45 UTC
something like (just off my head; prob. needs work): `while (<>) { chomp if (my $num= /^DESCRIPTION$/ .. /^ENDDESCRIPTION/); next if $num==0 \|\| $num =~ /E/; # skip endpoints print; }` [download] There was a thread on that a short time ago. Look up Range Operator in Perlop, and do a super search on flip-flop and variations for the past couple weeks. —John	[reply] [d/l]
Re: Removing linefeeds from part of a file by thpfft (Chaplain) on Jul 12, 2001 at 04:31 UTC
Methods that use <> will be most efficient but , for the sake of MTOW, here's another. To do this properly with a regex would either require you to unroll the loop or use a proper parser, but this is the sloppy version. It's more expensive, especially for a big file, but it'll work well enough and i'd feel happier not having to rely on a state toggle. `$text =~ s{DESCRIPTION(.*?)ENDDESCRIPTION} {"DESCRIPTION\n" . join(' ', split("\n",($1))) . "\nENDDESCR +IPTION"}ges;` [download]	[reply] [d/l]
Re: Removing linefeeds from part of a file by particle (Vicar) on Jul 12, 2001 at 02:27 UTC
sorry, this code is untested, but it may just work~ `#!/usr/bin/perl -w use strict; my $do_i_chomp?; # off by default while(<>){ # read from STDIN $do_i_chomp? && chomp; # chomp if you should m/^DESCRIPTION$/ && do{ !$do_i_chomp?; # flip chomping on print; # print the DESCRIPTION line }; print; # print the line m/^ENDDESCRIPTION$/ && do{ print "\n$_"; # print newline, then the ENDDESCRIPTION +line !$do_i_chomp?; # flip chomping off }; }` [download] `perl script.pl <infile >outfile` ~Particle	[reply] [d/l] [select]
Re: Removing linefeeds from part of a file by lemming (Priest) on Jul 12, 2001 at 01:47 UTC
`open file check each line if it's eq to "DESCRIPTION" turn on line chomping if it's eq to "ENDDESCRIPTION" turn off line chomping print each line close file` [download] Note you'll need a seperator for inside description	[reply] [d/l]