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

[Paul LAURENT]

Hi everybody,


I am using the STL "ofstream" class.

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)

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

 

[Thomas Matthews]

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 {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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[CBFalconer]

I am using the STL "ofstream" class.

c.l.c++ is over thataway --------->