What's up with /usr/src/usr.bin/alias?

[Jordan K. Hubbard]

As some people already know, the SUSv2 standards require that a number 
of commands which are typically implemented as shell built-ins also 
exist in /usr/bin (for reasons which are at best clear to The Open 
Group).  Unfortunately, the Open Group UNIX conformance test suite also 
tests that these things actually *work*, which can't be said for 
FreeBSD's current set, as we can see by the following interaction with 
/bin/sh:

# cat
^Z
[1] + Suspended               cat
# /usr/bin/fg
fg: No current job
# /usr/bin/jobs
# jobs
[1] + Suspended               cat
# fg
cat
^D
#

Using the fg and jobs builtins work, using the "command equivalents" do 
not.  The same is true for things like alias.  I suspect this is simply 
due to the implementation, which invokes the commands in a subshell and 
thus won't actually work in the context of a test harness which is 
actually verifying that they did what they said they were going to do 
afterwards.  Naturally, implementing something like "cd" as a command 
vs a builtin is also pretty darn hard so I'm not saying I don't 
understand why somebody might have punted on these, I'm simply 
wondering what the justification for trying to do this at all was given 
the shortcomings of the chosen approach.

--
Jordan K. Hubbard
Engineering Manager, BSD technology group
Apple Computer