How to zero out a file in tcsh?

[dgavin at davegavin.com]

 the "rm filename; touch filename" variation doesn't necessarily preserve
ownership or permissions depending on who does it and what their umask is.
My personal favorite is "cat /dev/null > filename".

Dave Gavin

Quoting John Jannotti <jj at lcs.mit.edu>:

> 
> 
> 
> Jerry Feldman <gaf at h0020780e341c.ne.client2.attbi.com> writes:
> > On Thu, 6 Feb 2003 22:29:15 -0500
> > Derek Martin <blu at sophic.org> wrote:
> > 
> > > One method to do this regardless of how your shell handles redirection
> > > and what flavor of echo you have is this:
> > > 
> > >   rm filename; touch filename
> > I fully concur with Derek. This is full portable accross all versions of
> > Unix and Linux. As mentioned in the other posts, echo, while a shell
> > builtin may have different behavior depending on the shell. 
> 
> But it doesn't do the same thing.  The other examples truncate the existing
> file, this doesn't.  It's possible this makes a difference.  One of the
> reasons you might be doing this is to reclaim disk space.  If a process has
> the file open, truncating it still reclaims the space, deleting it doesn't.
> 
> Or, perhaps you know that something is doing the equivalent of "tail -f" on
> the file, and another process is appending to it.  If you delete and
> recreate, those processes are not talking to each other any more.
> 
> I think "cat > filename", then ^d is probably the shortest portable
> way. (or echo -n > filename is you're not interactive).
> 
>   jj
> 
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