Re: mkdir when target exists and is a broken symlink

[Paul Eggert]

"Avis, Ed" <address@hidden> writes:

> There could be some kind of -f, --follow option so that mkdir will
> create the directory pointed to.

There is a potential security problem there, if the symbolic link
is in a directory writable by an attacker.

> You'd probably use it together with -p.  Then 'mkdir -fp' would be a
> way to try everything sensible to make sure the destination exists
> and can be used as a directory (ie, is a directory itself or a
> symlink to one).

Perhaps "mkdir -F -p" would also remove files that got in the way?  :-)

> Is this a sensible thing to put in mkdir or is there some existing Unix
> idiom that does what I want?

Not in POSIX/Unix, but in coreutils 5.3.0 and later: either "mkdir -p
$(readlink -f file)" or "mkdir -p $(readlink -m file)", depending on
the exact semantics that you want.  But think about the security
problems.

ftp://alpha.gnu.org/gnu/coreutils/coreutils-5.3.0.tar.gz

> I note that 'touch foo' when foo is a broken symlink will create the
> link destination if possible (though without making any directories,
> obviously).

POSIX requires this, but it is arguably a misfeature, due to the
security issues mentioned.  Perhaps we should add an option to "touch"
to disable it?