Re: md5sum

[Bill Hogan <bhogan@rahul.net>]

"IJ" == Ian Jackson <ian@chiark.chu.cam.ac.uk> writes:

  IJ> Bill Hogan writes ("Re: md5sum") [SuperCite undone]:
  >> [Ian Jackson <ian@chiark.chu.cam.ac.uk> writes:]
  >> > Bill Hogan writes ("md5sum"):
  >> > > What is the correct way to invoke md5sum to apply the checksums
  >> > > that are printed in Packages.gz?
  >> > Did you try
  >> md5sum <filename>
  >> > ?
  >> 
  >> Yes indeed.
  >> For example, I just downloaded the Debian-0.93 binutils package.
  >> 
  >> # md5sum binutils-2.5.2-3.deb
  >> 089acd78637918ecec283fc42b55dfd9  binutils-2.5.2-3.deb
  >> 
  >> I am interpreting this output to mean "the checksum computed by
  >> the program `md5sum' on the file `binutils-2.5.2-3.deb' was
  >> `089acd78637918ecec283fc42b55dfd9'."

  IJ> Yes ...

  >> [But w]hat is the md5sum checksum for that file supposed to be?
  >> 
  >> The only thing I have to compare it to is the md5sum checksum for
  >> that package which I find printed in my Packages.gz file.

  IJ> Yes ...

  >> Assuming equivalent `md5sum' programs were used to compute both
  >> of these checksums, it seems to me that if the two checksums don't
  >> match -- whether because the files on which they were calculated differ
  >> or because the checksum printed in Packages.gz file is outdated or
  >> incorrect or for some other reason -- then I am well-advised to assume
  >> the file is screwed up.

  IJ> Yes ...

  >> Hence my question: What is the correct -- i.e., best, proper,
  >> least error-prone -- way to invoke md5sum to *APPLY* the checksums
  >> that are printed in Packages.gz?

  IJ> You can't "apply" a checksum. 

  IJ> I have no idea what you're talking about, I'm afraid.

    "*Apply*. v. To put a thing in practical contact with another.
... 5. To put to a special use or purpose. ... 6. To put to
use. ... 7. To make use of (a word) in special reference to, or to
describe or characterize a thing. ... 8. To bring (a law, rule, test,
principle, etc) into contact with facts, to bring to bear practically,
to put into practical action. ..." [O.E.D.]

  IJ> You compare the output from `md5sum filename' or `md5sum
  IJ> <filename' with the md5sum field in the Packages file, and if it
  IJ> doesn't match you don't have the same file as was used to create the
  IJ> Packages file.

    Exactly, to apply the md5sum checksum printed in the Packages file
to the corresponding debian.deb file, I compare the output from
`md5sum debian.deb' or `md5sum <debian.deb' with the md5sum field
printed in in the Packages file, and if it doesn't match then I don't
have the same file as was used to create the Packages file.

    So, have it your way: What is the correct -- i.e., best, proper,
least error-prone -- way to to compare the output from `md5sum
debian.deb' or `md5sum <debian.deb' with the md5sum field printed in
the Packages file?

    BH

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