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    SubjectRe: RPMs :o(
       Date: 	Tue, 19 May 1998 23:54:40 +0100 (BST)
    From: Peter Horton <pdh@berserk.demon.co.uk>

    RPMs are basically gzipped cpio archives with a header.

    If you search the file for the byte 0x1f followed by 0x8b (these bytes
    mark a gzip file) and remove everything that precedes them, you will be
    left a gzipped cpio archive, which you can then unzip and unpack.

    Since this is so short, I'll take the liberty to repost the following
    rpm2cpio perl script.

    - Ted

    #!/usr/local/bin/perl

    # why does the world need another rpm2cpio? because the existing one
    # won't build unless you have half a ton of things that aren't really
    # required for it, since it uses the same library used to extract RPM's.
    # in particular, it won't build on the HPsUX box i'm on.

    # add a path if desired
    $gzip = "gzip";

    sub printhelp {
    print "rpm2cpio, perl version by orabidoo <odar\@pobox.com>\n";
    print "use: rpm2cpio [file.rpm]\n";
    print "dumps the contents to stdout as a GNU cpio archive\n";
    exit 0;
    }

    if ($#ARGV == -1) {
    printhelp if -t STDIN;
    $f = "STDIN";
    } elsif ($#ARGV == 0) {
    open(F, "< $ARGV[0]") or die "Can't read file $ARGV[0]\n";
    $f = 'F';
    } else {
    printhelp;
    }

    printhelp if -t STDOUT;

    # gobble the file up
    undef $/;
    $|=1;
    $rpm = <$f>;
    close ($f);

    ($magic, $major, $minor, $crap) = unpack("NCC C90", $rpm);

    die "Not an RPM\n" if $magic != 0xedabeedb;
    die "Not a version 3 RPM\n" if $major != 3;

    $rpm = substr($rpm, 96);

    while ($rpm ne '') {
    $rpm =~ s/^\c@*//s;
    ($magic, $crap, $sections, $bytes) = unpack("N4", $rpm);
    $smagic = unpack("n", $rpm);
    last if $smagic eq 0x1f8b;
    die "Error: header not recognized\n" if $magic != 0x8eade801;
    $rpm = substr($rpm, 16*(1+$sections) + $bytes);
    }

    die "bogus RPM\n" if $rpm eq '';

    open(ZCAT, "|gzip -cd") || die "can't pipe to gzip\n";
    print STDERR "CPIO archive found!\n";

    print ZCAT $rpm;
    close ZCAT;


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