Strange grep behavior

From: Helge Preuss (spam.preuss_at_fhi-berlin.mpg.de)
Date: 11/10/03 

Date: Mon, 10 Nov 2003 16:02:31 +0100

Hi,
a colleague of mine complained to me that grep does not print lines
matching the search expression in some of his files, giving the message
"binary file foo.txt matches". Now his files are just plain old text
files. What is even stranger, if he renames that file, grep prints the
matching lines.
Now I was not able to reproduce this behavior, but I found a different
unexpected behavior: grepping for a string in a binary file, which i
know it exists, two times out of three (different strings) it does not
find the search string. The third time, it just prints the string. No
line number, no mention of a binary file eiteher.
So my questions: Is this behavior known, maybe even documented? More
generally, how does grep determine whether a file is a binary?
The OS in case is Tru64 5.1a.
TIA
Helge 

-- 
hint: my first name is not "spam"!

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