[Bug-tar] Print estimate Tar size without reading data

[Tomas M]

Hi,
I'd like to suggest a feature for Tar.

The option --totals prints total size of tar archive, but it needs to go 
through the filesystem and read file data. When user only wish to see 
the size of TAR archive, (s)he must do something like

tar --totals -c /files/* -f /dev/null

or

tar -c /files/* | wc -c

This is OK with small files, but it's problematic if you want to 
estimate TAR size of several files bigger than 1GB. It reads the data 
even if it should only stat().

Just for the record, it may be useful to know the size of TAR archive 
BEFORE actually reading the data, for example to send correct 
'Content-Lenght' header for users browser before the Tar output, so user 
can see very nice progress bar during download of dynamically-created 
tar archive.

So I would like to suggest a new argument, --compute-total-size, which 
would only compute total size of TAR archive WITHOUT READING THE FILE DATA.

I believe coding shouldn't be hard for someone who understands the code 
now, but I'm far to stupid to make it myself (I tried).


Thank you for your consideration

Tomas M
slax.org