Re: RFC: Change pwd to assume -L by default

[Jim Meyering]

On Tue, Jul 1, 2014 at 12:02 PM, Bob Proulx <address@hidden> wrote:
> Jim Meyering wrote:
>> Pádraig Brady wrote:
>> > POSIX says that `pwd` without options should assume -L is specified.
>
> Hmm...  It does?  If so I think that is a bad thing in the standard
> since it does not standardize existing behavior but requires an
> incompatible change to it.  Existing behavior of /bin/pwd has always
> been to print the canonical path.
>
>> > pwd is most often invoked as a shell builtin and bash, dash, zsh, ksh
>> > all follow POSIX and assume that -L is the default.
>
>> > However coreutils pwd assumes -P is the default, according to this
>> > comment in the source:
>> >
>> >   "POSIX requires a default of -L, but most scripts expect -P."
>
> I still think that is true.  I think most usage of /bin/pwd expects it
> to be -P not -L.  This is separate from the usage of the shell builtin.
>
>> When I wrote the original pwd.c, the standard was
>> POSIX 1003.2-1992, and someone had actually sent
>> me hard copy for Volumes 1 and 2. I've just checked (still have them)
>> and see it says simply to print "an absolute pathname of the current
>> working directory", so I made it call xgetcwd and print that.
>>
>> I think it's fine to make -L the default, now.  As you say, it will make
>> our version conform to the newer standard and eliminate a small
>> source of incompatibility between the modern built-ins and exec'd
>> versions of this command. Any time we make such a change, there
>> is a risk of causing a script to malfunction, but I think very few scripts
>> exec pwd, and fewer still would malfunction with this change.
>
> I disagree.  I think most people expect that /bin/pwd produces the
> canonical path.  I think changing it to print $PWD as the shell
> builtin does is a bad idea since it will go against long standing
> usage.  I think if users were polled it would show that most people
> have the built in pwd defaulting to -L and therefore explicitly
> execute /bin/pwd in order to escape that logical illusion and to
> return the canonical path.
>
> I think this very small thing is actually a huge change in legacy
> behavior.  Please don't do it.

Hi Bob,

In coreutils tests, we had more uses than expected
of $(env pwd) or equivalent that expected the -P behavior.
Do you know of other uses of /bin/pwd that require -P's behavior?