Merging Selected Lines in a Text File

[xxqq]

I have a giant text file with thousands of line.
I want to merge selected multiple lines into a single line.
Lines that begin with a coma will be merged with previous line.
Lines that begin with other characters will not be merged with previous line.

Example: from:

aaaaa
, bbbb
, ccccc
dddd
, eeee

To:

aaaa, bbbb, cccc
dddd, eeee

How to do this operation? Can I use sed command?
Thank you.

[drl]

Hi, xxqq.

Brute force:

#!/usr/bin/perl

# @(#) p1       Demonstrate match including newlines.

use warnings;
use strict;

# slurp in entire file.
# Perl Best Practices, page 213.

my $file = do { local $/; <> };

# replace "newline," with ",".
# PBP, p 235 - 241

$file =~ s/\n,/,/xmsg;

print $file;

Results on your data file:

./p1 data1
aaaaa, bbbb, ccccc
dddd, eeee

Drawback: memory intensive ... cheers, drl