symlinks

[Olson, Arthur David (NCI)]

> -----Original Message-----
> From: Paul Eggert [mailto:eggert at twinsun.com]
> Sent: Thursday, March 14, 2002 7:19 PM
> To: Olson, Arthur David (NCI)
> Cc: tz at elsie.nci.nih.gov
> Subject: Re: symlinks
> 
> Unfortunately that code won't work if toname is of the form FOO/BAR,
> where FOO is a symbolic link to some other place in the filesystem.
> 
> The simplest fix is to remove the HAVE_SYMLINK code entirely, and to
> fail if the hard-link call fails.  It's one less thing to configure in
> Makefile and in private.h.  But if you want to support situations
> where hard links don't work, I think it would be simpler and more
> portable to make a copy instead of a link.

Checking the legislative history, I discovered that the item attached below
is what got the symlink ball rolling.
What I'm after is something that handles such real-world cases correctly;
I'm willing to let non-real-world cases slide.

				--ado

>From OLSONA at dc37a.nci.nih.gov  Sat Jan 17 14:32:28 1998
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From: "Olson, Arthur David" <OLSONA at dc37a.nci.nih.gov>
To: 'tz' <tz at elsie.nci.nih.gov>,
        "'aj at arthur.rhein-neckar.de'"
	 <aj at arthur.rhein-neckar.de>
Subject: FW: zic using hardlinks:-(
Date: Sat, 17 Jan 1998 14:31:18 -0500
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Status: RO

Andreas Jaeger is not on the time zone list; be sure to include Andreas
in any reply.

				--ado

----------
From: 	Andreas Jaeger[SMTP:aj at arthur.rhein-neckar.de]
Sent: 	Thursday, January 15, 1998 3:34 PM
To: 	tz at elsie.nci.nih.gov
Subject: 	zic using hardlinks:-(


Hi,

I received the following bug report for GNU libc. Jochen says
that using a hard link doesn't work for his system since /etc and
/usr/share are on different filesystems. zic is from tzcode1997h.

I see three possibilities:
- changing the link call in zic.c to symlink. 
- if link fails with error EXDEV (oldpath and newpath are not on the
  same filesystem) retry with a symlink.
- leave it the way it is.

Should symbolic links used in general or only for localtime?

Andreas
-- 
 Andreas Jaeger   aj at arthur.rhein-neckar.de

>Number:         413
>Category:       libc
>Synopsis:       `zic -l' tries to hard link a file between different
disk partitions
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    libc-gnats
>State:          open
>Class:          sw-bug
>Submitter-Id:   unknown
>Arrival-Date:   Thu Jan 15 07:32:17 EST 1998
>Last-Modified:
>Originator:     Jochen Voss
>Organization:
 Department of Mathematics, University of Kaiserslautern/Germany
>Release:        libc-2.0.6
>Environment:
Host type: i486-pc-linux-gnu
System: Linux tatonka 2.0.33 #2 Fri Jan 9 20:20:45 MET 1998 i486
Architecture: i486

Addons: localedata crypt linuxthreads
Build CFLAGS: -O3 -m486 -fomit-frame-pointer
Build CC: gcc -B$(common-objpfx)
Build shared: yes
Build profile: no
Build omitfp: no
Stdio: libio

>Description:
	The command "zic -l MET" should set the local time zone by
	linking the file "/usr/share/zoneinfo/MET" to
	"/etc/localtime".  It uses a hard link for this purpose.  On
	my system this fails, because the directories "/etc" and
	"/usr/share/zoneinfo" are located on different disk partitions
	on my system.  This results in the output
	
	  zic: Kann nicht von /usr/share/zoneinfo/MET nach
/etc/localtime linken: Ungltiger Link ber Gertegrenzen hinweg
	
	when I execaute the above command (obviously I use `LANG=de').
>How-To-Repeat:
	Find a system, which uses disk partitions as described above,
	and execute the command "zic -l MET".
>Fix:
	Modify the code in "time/zic.c" to use symlinks (if available)
	or to copy the file if the hard link fails.
>Audit-Trail:
>Unformatted: