Re: How do I delete lines from a file using "ofstream" ?

From: Thomas Matthews (Thomas_MatthewsHatesSpam_at_sbcglobal.net)
Date: 11/06/03 

Date: Thu, 06 Nov 2003 21:12:41 GMT

Paul LAURENT wrote:
> Hi everybody,
>
>
> I am using the STL "ofstream" class.
There is no STL, ofstream, or class in standard C. You may want the
folks across the hall in news:comp.lang.c++.
{However, the answer to your issue is still the same, see below}.

> I open a file using "ofstream" in update at the end mode ("ate"), I can read and
> write my file correctly.
>
> => What I would like to do is deleting some lines from the file which decreases
> the size of the file.
>
> For performance reasons, I DO NOT WANT to close and open the file each time I
> want to delete some information in it (I know that you can overwrite the file
> content by re-opening the file)
Yes, but overwriting does not guarantee adjusting the end of the file to
the last used record.

> I only found methods which allow you to add some information but no methods for
> deleting the information.
>
> Any idea will be welcome !
>
>
>
> Thanks in advance.
>
>
>
> Paul
>
>

Unfortunately, there is no process in _standard_ C to truncate a file
by delete portions of it. The portable method is to copy the portions
of the old file to a new file and then delete the old file {you could
rename the new file at this point}.

However, your platform may have some specific functions to perform
what you want. Ask the experts in a newsgroup about your platform. 

-- 
Thomas Matthews
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