You can open both files in Perl, which has no line length limits:

{
    my ( $in, $out );
    open $in, '<', $filepath or die $!;
    open $out, '>', $newpath or die $!;
    while (<$in>) {
        # process $_ which is the current line
        $_ = quux($_);
        print $out; # assumes $_ has everything to print now
    }
    close $out or die $!;
    close $in;
}

[download]
There are lots of ways to do this, many shortcuts. I showed this one because it's explicit about what it does. The use of lexical $in, $out as filehandles is relatively new, as is the three-argument open. For older perl, use globs like \*IN, \*OUT for filehandles, and concatenate the direction arrows '<', '>' with a space and the file path.

Update: After a lot of heat and little light, it seems that what you want is getgrent. If it fails, your /etc/group file is probably broken. See also 'perrldoc User::grent'.

After Compline,
Zaxo

In reply to Re: 2048 character limit by Zaxo
in thread 2048 character limit by druid

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.