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Date: Sun, 07 Jul 1996 08:36:56 -0400
From: Gary Chrysler <tcg@ime.net>
Reply-To: tcg@ime.net
Organization: The Computer Guy
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To: "Hr.Ladavac" <lada@ws2301.gud.siemens.co.at>
CC: "Thomas S. Traylor" <tst@titan.cs.mci.com>, questions@FreeBSD.ORG
Subject: Re: How do you write to an executable (binary)?
References: <199607071119.AA080148382@ws2301.gud.siemens.co.at>
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Hr.Ladavac wrote:
> 
> In his e-mail Thomas S. Traylor wrote:
> > Here's what I'm trying to do:
> >
> > I have a program that will prompt the user for a value.  I would like to
> > write that value to the executable (binary) file.  (Using open, lseek,
> > write, close)
> >
> > Problem:
> >
> > When I open the file I get the following error:
> >
> > "Error: Text file busy".  The message number is [ETXTBSY].
> >
> > I'm able to do this with other OS.  How can I get this to work with
> > FreeBSD? Any ideas or suggestions would be greatly appreciated.
> 
> AFAIK, you cannot change the executable image from under itself (nor
> while file is in use--being executed).
> 
> What you can do is:
> 
>         1) copy executable to executable.new
>         2) edit executable.new to your heart's content (it is not in use :)
>         3) move executable.new to executable.
> 
> Beware: all processes that started executing the executable prior to point
> 3) will not see the changes in the image (namely, they will still be using
> or having access to the *old* executable, which is basically marked deleted
> but referenced/in use and remains on disk until it is no longer referenced).
> 
> /Marino

Seems to me like it would be easier to whip up a setup program.

-Enjoy
Gary
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