Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!iuvax!cica!gatech!udel!mmdf
From: HELMER%SDNET.BITNET@vm1.nodak.edu (Guy Helmer)
Newsgroups: comp.os.minix
Subject: Re: Replacement for rename()?
Message-ID: <20510@louie.udel.EDU>
Date: 26 Jul 89 13:22:36 GMT
Sender: mmdf@udel.EDU
Lines: 69

Thos Sumner writes:
>In article <20454@louie.udel.EDU>, HELMER%SDNET.BITNET@vm1.nodak.edu (Guy
> Helmer) writes:
>> I've ported David Clunie's yacc to MINIX successfully except for
>> one problem: no obvious working replacement for rename()
>
>   system -- issue a shell command (Section 3, Unix User's Manual)
>   mv -- move or rename files (Section 1, Unix User's Manual)
>thus
>   system("mv <oldfile> <newfile>");
>

Ugh...  Not exactly the beautiful, simple, fast executing trick I was
looking forward to seeing...

>> I've tried using link(oldname, newname); unlink(oldname);,
>> but link() apparently doesn't like to work over mount points even
>> if the new file and old file are to exist on the same file system.
>
>I find this confusing: going over mount points appears to be the essence
>of different file systems.  What do you mean here?  It is correct for
>links (i.e. hard as opposed to symbolic links) not to connect between
>file systems.
>

Under minix, link("/tmp/oldfile", "/tmp/newfile") doesn't work for
me.  When I tried it, this path traversed a mount point on my system, but
I (apparently incorrectly) hoped that it would still work.
I don't have V7 docs nor do I have real un*x to try this out,
so I don't really know what is supposed to work.

>> The only thing that seems to be left to do is the equivalent
>> of 'cp <oldfile> <newfile>' and then unlink(oldname).  Does anyone
>I presume this should be "<oldfile>"  --------^^^^^^^
>> have a better suggestion?  Thanks in advance.
>
>The latter sequence is about equivalent to _mv_ for the case where
>the two names refer to different filesystems (mv also sets the time
>and date info on the new copy). Of course, as written the example
>is mixing program execution (cp) and library call (unlink).

I was thinking of writing code to do the equivalent of a 'cp', and
then do the unlink().  I'm trying to avoid fork() and exec() like
the plague :-) ; yacc really doesn't need to be any slower.

I have a new thought, though;  would link() work if I did something
like this:

   getcwd(curpath);
   chdir("/tmp");
   link("oldname", "newname");
   unlink("oldname");
   chdir(curpath);

It seems to me like this would be the best replacement possible for
rename on Minix.

>
>
> Thos Sumner       Internet: thos@cca.ucsf.edu
> (The I.G.)        UUCP: ...ucbvax!ucsfcgl!cca.ucsf!thos
>                   BITNET:  thos@ucsfcca
>
> U.S. Mail:  Thos Sumner, Computer Center, Rm U-76, UCSF
>             San Francisco, CA 94143-0704 USA
>
>OS|2 -- an Operating System for puppets.
>
>#include <disclaimer.std>