From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Mon, 10 Apr 2000 17:36:53 +0000
From: Tom Duff td@pixar.com
Subject: [9fans] truncate syscall
Topicbox-Message-UUID: a1536a66-eac8-11e9-9e20-41e7f4b1d025
Message-ID: <20000410173653.bwaF7C25C3FExCYm402lhMt9Rl3ehxea_fbAU6N5rpg@z>

> mmap(). truncate() is a bad name - it's setsize(). IOW, it can extend
> files. Add the mmap() semantics in that respect and there you go -
> open()/ftruncate() to set the size/mmap() the region/start working; is
> quite common. Yes, you can kludge around it with lseek();write(); but
> that's a kludge, unless we accept that zero-length write() changes the
> file size. Which is not true under a lot of Unices (I seriously suspect
> that it's explicitly prohibited by POSIX or something like that).

	int f=create("file", OREAD, 0666);
	if(n){
		seek(f, n-1, 0);
		write(f, "", 1);
	}

What exactly is kludgy about this?

I've been using UNIX & Plan 9 for 26 years,
and not once have I wanted to chop the tail
off a file.  I find it really hard to believe
that you need this so badly that you want to
change 9p.  Why can't you afford to rewrite
the file?


-- 
Tom Duff.  This work was funded by The Corporation for Public Vaporware.