Re: [PATCH] Add a "-h" flag to mv

On Wednesday, August 29, 2012 3:32:13 pm Jilles Tjoelker wrote:
> On Wed, Aug 29, 2012 at 08:09:20AM -0400, John Baldwin wrote:
> > On Wednesday, August 29, 2012 6:02:47 am Jilles Tjoelker wrote:
> > > GNU coreutils mv (and also cp/install/ln) appears to use
> > > -T/--no-target-directory for a similar purpose: -T prevents the target
> > > being treated as a directory (whether it is a symlink or not).
> 
> > Hmm, I could find no documentation for this online via Google searches or
> > the Linux manpages we have on www.FreeBSD.org.  Bah, Google just makes
> > searching for these sorts of things painful it seems (you have to put
> > explicit quotes around "--no-target-directory" for it to actually be used).
> > Also, it seems I just chose all the wrong Linux manpage sets to look at.
> 
> > It seems that Linux's -T flag is similar to -h for ln as well.  I don't think
> > we can deprecate -h for ln, but perhaps we could add -T as a compat flag to
> > ln and mv?  I'd be inclined to still add -h to mv so that it mirrors ln.
> 
> > Hmm, it seems RedHat's ln uses -n for this (OpenBSD, NetBSD, and Darwin
> > all include a -n as an alias to -h for ln to support compat with other
> > operating systems).  OSF/1 (and Tru64) and SunOS use -n to mean "complain
> > if the file already exists" similar to 'mv -n'.  Also, looking at the
> > Suse manpage on www.FreeBSD.org, it seems their ln (which does have -T)
> > has both -n and -T with different descriptions, but to achieve the same
> > purpose:
> 
> > http://www.freebsd.org/cgi/man.cgi?query=ln&apropos=0&sektion=0&manpath=SuSE+Linux%2Fi386+11.3&arch=default&format=html
> 
> >        -n, --no-dereference
> > 	      treat destination that is a symlink to a directory as if it were
> > 	      a normal file
> 
> >        -T, --no-target-directory
> > 	      treat LINK_NAME as a normal file
> 
> > (To me it seems LINK_NAME and destination are the same thing.)
> 
> > My inclination would be to add -h to mv, but perhaps add -T as an alias
> > for -h to both ln and mv, and -n as an alias for -h to ln (if we want
> > aliases to match coreutils).
> 
> Coreutils ln -n is the same as our ln -h, and we already have
> compatibility for it.

Bah, not sure how I missed the -n previously.

> The coreutils -T option is different, though. It forces the ln
> source_file target_file synopsis instead of the ln source_file ...
> target_dir synopsis, without checking the type of the final operand. If
> there are not exactly two operands, a syntax error occurs. If the final
> operand is a directory and cannot be overwritten, an error occurs.

Ah, this is not quite what my mv -h patch does.  It does not error if the
destination is a directory.  It is much closer to ln -h and exactly matches
the language for ln -n I quoted above.

-- 
John Baldwin