heh. i didn't realize i sucked this bad =)
On 9/1/05, John W. Krahn <[EMAIL PROTECTED]> wrote:
> > Anyway, the issue I have is that I need to determine where there are
> > gaps between the first sector and last sector (on the entire disk, not
> > on a given partition).
>
> How do you determine which partitions to skip and which not to skip?
Well, my initial thought was to skip partition 2 entirely (which is
reserved in Solaris as a means to address the entire disk, and would
therefore bork up the calculations). I've since realized that I can't
quite do that, I need to at least check if part2 is the only one
present first. Either way, it won't be part of the calculations
though.
Really, I should check all the partitions and see if the difference
between start and end sectors is == the total number of sectors ...
>
> > use strict();
>
> You are telling perl to load the 'strict' module and then you are telling the
> 'strict' module not to do anything (with the empty parentheses.) Why use the
> module if you don't want it to do anything?
*doh* . thanks.
> > sub get_vtoc($) {
>
> You really, really, *REALLY* shouldn't use "prototypes". If you want to check
> the arguments passed to your subroutine you should do something like this:
>
> @_ == 1 or die "Wrong number of arguments passed to get_vtoc().\n";
>
>
> "Far More Than Everything You've Ever Wanted to Know about Prototypes in Perl"
> http://library.n0i.net/programming/perl/articles/fm_prototypes/
A very good read, noted and changed.
>
> > # if this is the bytes/sector line, split it
> > # and store the bytes per sector as $BPS
> > if($_ =~ /bytes\/sector/) {
> > our (undef, $BPS, undef) = split(/\s/, $_, 3);
>
> our() is lexically scoped just like my() and the only reason that this
> actually works is because strict is turned off and $BPS is a package variable.
> To make this work correctly with strict you have to declare $BPS outside of
> the while loop.
>
> If you use split correctly that could be written as:
>
> $BPS = ( split )[ 1 ];
>
> Then you wouldn't need the substitutions at the beginning of the loop.
>
> However *I* would write it like this:
>
> if ( /(\d+)\s+bytes\/sector/ ) {
> $BPS = $1;
> }
I think this is the best example of regexp backreferencing I've seen.
At last, they make sense to me =)
I've changed this in the real script, and a few other places elsewhere to boot!
> > }
> >
> > # skip the the line if it starts with an * or is partition 2
> > next if(/^[\*|2]/);
>
> Your comment is incorrect, it should read "if it starts with an * or a | or is
> partition 2". Regular expression meta-characters are not special in a
> character class so you probably meant /^[*2]/.
I did indeed mean that. And now that you've got it working the right
way I realize it's totally not what I wanted. I need to leave the 2
out of it, because if partition 2 is the only one defined, I need to
return it. Many thanks for helping me catch this.
>
> > # put the pieces into the slices hash
> > $slices{$part} = {
> > bps => "$BPS",
> > tag => "$tag",
> > flag => "$flag",
> > part => "$part",
> > fsector => "$fsector",
> > lsector => "$lsector",
> > sectcount => "$sectcount",
> > mount => "$mount"
>
> perldoc -q quoting
>
> Found in /usr/lib/perl5/5.8.6/pod/perlfaq4.pod
> What's wrong with always quoting "$vars"?
Read ... I don't quite get it, but I understood enough to realize that
I needed to unquote them or potentially suffer difficult to trace
errors later on. Done.
> This appears to do what you want (although there may be a module that does
> this better):
>
> my @sec_range;
> for my $sectors ( map [ @{ $_ }{ 'fsector', 'lsector' } ],
> sort { $a->{ fsector } <=> $b->{ fsector } }
> values %$slices ) {
>
> if ( @sec_range && $sec_range[ -1 ][ 1 ] == $sectors->[ 0 ] - 1 ) {
> $sec_range[ -1 ][ 1 ] = $sectors->[ 1 ];
> }
> else {
> push @sec_range, $sectors;
> }
> }
>
> print "Available sectors:\n";
> print "\t0 - ", $sec_range[0][0]-1, "\n" if $sec_range[0][0];
> print "\t", $sec_range[$_-1][1]+1, ' - ', $sec_range[$_][0]-1, "\n"
> for 1 .. $#sec_range;
This does indeed do the right thing on the sample data. I'm working
through it slowly, and I kinda get it. I gotta admit, I'm lost in the
crypticism, but it looks like it throws the firstsectors and
lastsectors into a hash, sorts the keys and values independantly, then
compares ?
I'm trying it on a second drive however, and am getting results that
don't look right ...
That drive has the following partitions defined:
* First Sector Last
* Partition Tag Flags Sector Count Sector Mount Directory
0 2 00 1048707 68030172 69078878 /
1 3 01 0 1048707 1048706
2 5 00 0 71127180 71127179
7 8 00 69078879 2048301 71127179 /export/home
I would expect the script to return no available sectors, but am
getting this instead:
Available sectors:
1048707 - -1
71127180 - 1048706
Still looking into why, not sure, since I'm just trying to figure out
which end is up =0)
Thanks for the input and guidance. I'll keep hacking away on this and
see if I can't get it to work, now that I've got an idea on how to
start.
- jason
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