checksum/disk theories?

[John Summerfield]

Tom Horsley wrote:
> I have the f12 Beta dvd images run through "split -b 1G" on
> a vfat usb stick. For both the i36 and the x86_64 images
> when I do something like this:
> 
> cat Fedora-12-Beta-x86_64-DVD.isoa* > ~/Fedora-12-Beta-x86_64-DVD.iso
> 
> The sha256sum -c fails on the resulting file :-(. (The checksums
> checked OK on the original files I downloaded).
> 
> Then I do this:
> 
> cat Fedora-12-Beta-x86_64-DVD.isoaa > ~/Fedora-12-Beta-x86_64-DVD.iso
> cat Fedora-12-Beta-x86_64-DVD.isoab >> ~/Fedora-12-Beta-x86_64-DVD.iso
> cat Fedora-12-Beta-x86_64-DVD.isoac >> ~/Fedora-12-Beta-x86_64-DVD.iso
> cat Fedora-12-Beta-x86_64-DVD.isoad >> ~/Fedora-12-Beta-x86_64-DVD.iso
> 
> The resulting file is the same size as the one I got the 1st time,
> but this file passes the sha256sum -c.
> 
> Has bash started randomly ordering wildcard expansion or something?

I don't think bash has ever ordered the files. Instead, they're listed 
in the order matched.

Where order matters, something modelled on this:
echo $(\ls Derf*)
or echo $(ls -1 Der* | sort)

ls supports ordering on other criteria than filename, even for short lists.

That said, my testing on RHEL6-clone just now doesn't support my 
contention, so maybe I misremember something.

btw FAT32 does support files larger than 1 Gb, and you can format them 
ext2 if you wish. I'd not bother with journals in the ordinary course of 
events.

<after further research>

DESCRIPTION
        The  scandir()  function  scans the directory dir, calling 
filter() on each directory entry.  Entries
        for which filter() returns non-zero are stored  in  strings 
allocated  via  malloc(),  sorted  using
        qsort() with the comparison function compar(), and collected in 
array namelist which is allocated via
        malloc().  If filter is NULL, all entries are selected.

Why you appeared to have the files concatenated in the wrong order, I'm 
running out of ideas.
This might help elucidate:

echo \
cat Fedora-12-Beta-x86_64-DVD.isoa* \> ~/Fedora-12-Beta-x86_64-DVD.iso

Note I escaped the ">" so as to prevent its interpretation by your 
shell. This command will show you what bash thinks it's doing.



-- 

Cheers
John

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