Re: GNU grep 2.5.1

[Hans-Bernhard Broeker]

Marvin Hile <address@hidden> wrote:
> I have quite a number of ~1 gigabyte data files on my system.
> They have a certain internal structure, and each section starts
> with a known pattern. This is so my software can "parse" them
> quickly. To check to make sure they are not corrupted, I have
> been doing

> od -x bigDataFile | grep -c "aa55 0000 0490"

> grep -c "\xaa\x55\x00\x00\x04\x90" bigDataFile

> should be faster. Well, it is faster, but it always says 0.

That may very well be because you forgot about endianness.  Let me
venture a guess:

        od -tx1 bigDataFile | grep -c "aa 55 00 00 04 90"

will report 0 but

        od -tx1 bigDataFile | grep -c "55 aa 00 00 90 04"

will report the large number you expect.

I'm not at all convinced that passing '\0' characters to grep via the
command line can ever possibly work.  C programs do tend to react
badly to strings with string terminators anywhere else but at their
end.

Would be it be heresy to suggest you just write a little C program for
doing this, instead?

-- 
Hans-Bernhard Broeker (address@hidden)
Even if all the snow were burnt, ashes would remain.