Date: Mon, 12 Dec 1994 15:02:12 GMT+0100
From: IBBT0 AT cc DOT uab DOT es
Subject: Help about truncating files
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Organization: Universitat Autonoma de Barcelona

Hello, people!

I am writting a program that allows doing different changes over pree=
xisting
files. One of the options is to erase an important part of the end of
the file. To do this one possible solution is to rename the file and =
to
rewrite the first part over a new file with the original name. Of cou=
rse
this is slow and probably there is a better solution, but I cannot fi=
nd it.

In other words, I am asking you for a instruction, if possible workin=
g in
ANSI C and using streams (fopen(),...), not file handles, to inform t=
he
operating system and the File Allocation Table I want truncate the fi=
le.

Note I work with binary data files and I want a real truncation, not =
only a
visual one in the case of "type"; I want my next "dir" command report=
ing a
smaller number of bytes. So the solution of putting a "Ctrl+Z" in the=
 end
of a text file is not useful for me.

I have test putting my FILE pointer to the approprite part of the fil=
e
with fseek() and doing the following:

   FILE *stream;
   long int offset;
            :
      fgetpos (stream, &offset);
      fsetpos (stream, &offset);
            :
but it does not work.

I work under a DOS-Windows environment.

Thank you very much for your help!!



Xavier Pons
Centre de Recerca Ecol=95gica i Aplicacions Forestals, CREAF.
Universitat Aut=95noma de Barcelona.
09193. Bellaterra
Catalonia. Spain.