the file truncate API is limited and inconvenient

[Krzysztof Åelechowski <giecrilj at stegny dot 2a dot pl>]

I am reading the description of the file truncate API at "14.9.10 File Size" 
[1]:

:However, sometimes it is necessary to reduce the size of a file. This can be 
done with the truncate and ftruncate functions. They were introduced in BSD 
Unix. ftruncate was later added to POSIX.1. 

1. How is it possible that they were not needed before BSD UNIX?

2. It is obvious for me that there should be a stdio API with the meaning "let 
here be the end of this FILE".  I can do this under POSIX by using ftruncate 
but it requires writing my own subroutine (ftuncate (fileno (), ftell())), and 
of course there is no C++ way to do this.  How is it possible that nobody ever 
needed this to be a standard API?

I understand that you can end a text file with ^Z (which is because at IBM 
file size had to be a multiple of 128) and that binary formats can just ignore 
excessive data.  However, disk space was very expensive those days, so wasting 
it for unneeded data would not be very wise IMHO, and the alternative of 
copying the file can run out of disk space when the data part is big enough.

Please enlighten me on the subject.

Astonished,
Chris

== References ==
[1] <URL:http://www.gnu.org/software/libc/manual/html_node/File-
Size.html#File-Size>