svn commit: r203990 - head/lib/libc/sys

[Bruce Evans]

On Thu, 18 Feb 2010, Bruce Evans wrote:

> On Wed, 17 Feb 2010, Poul-Henning Kamp wrote:
>
>> Log:
>>  Mention EISDIR as a possible errno.
>
> It's not a possible error.
>
>> ...

Related bug: unlink(1) bogusly prints a messages that looks like
strerror(EISDIR).  It doesn't even try unlink(2) on directories,
but prints this message from a private string.

%%%
Script started on Thu Feb 18 05:49:45 2010
ttyp0:bde at besplex:/tmp/z> mkdir z
ttyp0:bde at besplex:/tmp/z> /bin/unlink z
unlink: z: is a directory
ttyp0:bde at besplex:/tmp/z> truss /bin/unlink z
lstat("z",0xbfbfe840)				 = 0 (0x0)
unlink: write(2,0xbfbfe0b0,8)				 = 8 (0x8)
z: is a directorywrite(2,0xbfbfe0d0,17)				 = 17 (0x11)

write(2,0x80a6753,1)				 = 1 (0x1)
exit(0x1) 
process exit, rval = 256
%%%

Here I use /bin/unlink since the unlink in $PATH is missing the bug.

/bin/unlink is a link to /bin/rm.  rm(1) takes a -d flag which should
do the right thing for unlink, but this flag is neither settable nor
forced for unlink(1).

The above behaviour of unlink(1) is not permitted by POSIX or unlink(1)'s
man page:

POSIX (old draft, no change in current version):
%%%
36900            The unlink utility shall perform the function call:
36901            unlink(file);
36902            A user may need appropriate privilege to invoke the unlink utility.
%%%

Man page:
%%%
      When the utility is called as unlink, only one argument, which must not
      be a directory, may be supplied.  No options may be supplied in this sim-
      ple mode of operation, which performs an unlink(2) operation on the
      passed argument.

STANDARDS
      The rm command conforms to IEEE Std 1003.2 (``POSIX.2'').

      The simplified unlink command conforms to Version 2 of the Single UNIX
      Specification (``SUSv2'').
%%%

Oops, the man page actually says that the arg must not be a directory.

POSIX doesn't make this restriction, except by possibly requiring
appropriate privilege, which can be interpreted as "more privilege
than exists" if the file is a directory so as to make FreeBSD conform
(except the error must involve unlink(1) not being invokable in this
case :-).  POSIX doesn't specify the form of the diagnostic message for
any case.

Anyway, unlink(1) shouldn't fall into rm(1)'s error handling to to
print its diagnostic.  It should use a special message (matching its
man page) for directories, or just try unlink(2).

rm(1)'s current special message should say something about directory
removal requiring -d, and not look like strerror(EISDIR).  Or since
directory removal is prohibited by the kernel, the -d option can never
work, so it should have been removed ~10 years ago when the kernel was
changed to prohibit it.

Bruce