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To: Gary Kline <kline@thought.org>
References: <20081227011335.GA29354@thought.org>
From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org>
Date: Fri, 26 Dec 2008 20:32:45 -0500
In-Reply-To: <20081227011335.GA29354@thought.org> (Gary Kline's message of
	"Fri\, 26 Dec 2008 17\:13\:39 -0800")
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Cc: FreeBSD Mailing List <freebsd-questions@FreeBSD.ORG>
Subject: Re: how can i be certain that a file has copied exactly?
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Gary Kline <kline@thought.org> writes:

> 	is there a way i can be sure that my little C program has copied a
> 	dos/win file named, say, foo.htm\;7 to simply foo.htm?
>
> 	my program uses fopen/fgets/fputs to copy the markup files.  of
> 	the several i have copied, no problem.  unless i hack cmp or diff, 
> 	i have to avoid the shell.
>
> 	any ideas? in other words, does anybody have a prefab cmp(oldfile, newfile)
> 	fn?

mtree(1) handles whole ranges of files.

For a single file, you could use some kind of checksum in your program
or externally, but in general it will be comparing against the cache of
the file's buffers, not against what is really on disk, so if you
suspect an operating system or hardware-write bug, you won't spot it
immediately.

What, precisely, would you like to protect against?
-- 
Lowell Gilbert, embedded/networking software engineer, Boston area
		http://be-well.ilk.org/~lowell/