POSIX/v7 equiv for ftruncate?

[Bob Webber]

Given the current trend toward Unix on multiuser machines, running out
of file space on a partition is becoming endemic.  The question arises
of what is the optimal way of making use of the file space you already
have and returning some of it where possible.  A program INSERT was
recently posted to alt.sources that hinges on the use of ftruncate
(2-BSD) to collapse the file to the appropriate size after having
written into it.  Is there any POSIX/v7 idiom for this?

---- BOB (webber at athos.rutgers.edu ; rutgers!athos.rutgers.edu!webber)