Re: [PATCH, contrib] download_prerequisites: check for existing symlinks before making new ones

[Eric Gallager <egall@gwmail.gwu.edu>]

On 7/13/16, Jeff Law <law@redhat.com> wrote:
> On 06/27/2016 08:10 PM, Eric Gallager wrote:
>> The last time I ran ./contrib/download_prerequisites, I already had
>> previous symlinks set up from a previous run of the script, so `ln`
>> followed the existing symlinks and created the new ones in the
>> directories to which the symlinks pointed. This patch should fix that
>> by removing the old symlinks before creating new ones. (For some
>> reason the `-f` flag to `ln` that was already there wasn't enough for
>> me.) Tested by running the script and ensuring that the new isl
>> symlink pointed to the correct directory, and that there were no bad
>> symlinks in the old isl directory. Could someone commit this trivial
>> patch for me, or something like it? I don't have write access.
> I'd really rather know why the "-f" flag didn't work for you.  The whole
> point of -f is to remove the destination file first.
>
> Jeff
>

Reading my ln manpage, it describes the "-f" flag like this:


     -f    If the target file already exists, then unlink it so that the
           link may occur.  (The -f option overrides any previous -i
           options.)

Okay, so that seems like it should do what you say, but the manpage
also describes a separate uppercase "-F" option:

     -F    If the target file already exists and is a directory, then
           remove it so that the link may occur.  The -F option should be
           used with either -f or -i options.  If none is specified, -f is
           implied.  The -F option is a no-op unless -s option is speci-
           fied.

So it seems to imply that "-f" will only remove the destination file
if it's a regular file, while "-F" is needed if the destination file
is a directory. The page also has this to say about "-F" later:

     The -F option is FreeBSD extention and should not be used in portable
     scripts.

So this could be a BSD vs. GNU thing.