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.IP \fBSubject:\fP 15
Add /usr/xpg4/bin/crontab and /usr/xpg6/bin/crontab
.IP "\fBSubmitted by:\fP" 15
Carol Fields
.IP \fBFile:\fP 15
\*(aR/\*(cA/opinion.ms
.IP \fBDate:\fP 15
November 30th, 2005
.IP "\fBCommittee:\fP" 15
Bill Sommerfeld,
Robert Berube Jr,
James D Carlson,
Ed Gould,
Joseph Kowalski,
Glenn Skinner,
Gary Winiger,
Shudong Zhou.
.IP "\fBProduct Approval Committee:\fP" 15

Solaris PAC
.br
solaris-pac-opinion@Sun.COM
.pn 2
.NH
Summary
.LP
This project proposed to deliver xpg4 and xpg6 variants of the
"crontab" command which invoke the xpg4 and xpg6 variants of "vi" as
their default editors.  In addition, the project will deliver a change to
the /usr/bin variant of crontab to use "vi" rather than "ed" as
the default editor.
.NH
Decision & Precedence Information
.LP
This project is approved as specified in references [1] and [2].
.LP
The entirety of this project may be delivered in a Minor release of the
Solaris OS.  In addition, the two xpg variants of crontab may be
delivered in a Patch release of the Solaris OS.
.Ec
.NH
Interfaces
.LP
The project exports the following interfaces.
.if n .ne 8
.if t .ne 3
.TS H
box;
c s s
l | l | l.
Interfaces Exported
_
Interface	Classification	Comments
_
.TH
/usr/xpg4/bin/crontab	Standard	T{
XPG4 behavior
T}
/usr/xpg6/bin/crontab	Standard	T{
XPG6 behavior
T}
/usr/bin/crontab	Standard	T{
change default editor from ed to vi to parallel XPG behavior
T}
.TE
.NH
Opinion
.LP
.NH 2
Background
.LP
During the era of SunOS 4.1, our standards-compliance approach relied
exclusively on the setting of $PATH.  Based on customer feedback, we
subsequently added the additional ability for users to "cherry-pick" specific
commands from the variant directories.  At present, we document a
combined approach: setting $PATH as specified in standards(5) for a
complete standards-compliant environment, and, in addition, variant
forms of individual commands are documented by pathname in the
individual command manpages.
.NH 2
Original Proposal
.LP
The original proposal left the existing behavior of /usr/bin/crontab
-e unchanged, using the first "ed" in $PATH as the default editor.
.NH 2
Amendment
.LP
Several reviewers expressed concern with the divergence in behavor
between /usr/bin and xpgN variants introduced by this case.  The
project team accepted a suggestion during the meeting to amend the
spec to add, in addition to the delivery with Patch binding of the
xpg4 and xpg6 variants of crontab, a change with Minor release binding
to /usr/bin/crontab to use the first vi on $PATH as the default
editor.
.NH 2
Standards Strategy Unclear To Many
.LP
Additionally, several reviewers expressed concern with the slowly
growing proliferation of additional variant commands in the
/usr/xpg4/bin and /usr/xpg6/bin directories, triggered solely by the
behavior of a spawned subprocess.  This concern was reinforced by the
observed behavior that many of the variant commands in /usr/xpg4/bin
support options which are simply rejected by the default variant; for
instance, /usr/xpg4/bin/id supports a '-u' option; while /usr/bin/id
rejects -u with an "illegal option" usage message.
.LP
The heated discussion which followed made it clear that our strategy
for standards compliance is not well understood among solaris
developers as well as among solaris users & developers of applications
for solaris.  Selective cherry-picking is documented, but there is
additionally a significant concern among a number of members of the
Committee that the cherry-picking of complex commands which invoke
other commands is of very limited applicability.  Both ability to
cherrypick and the limitations on this are not well expressed in our
documentation, including the standards(5) man page.  This led to the
advice given in section 6.1.
.LP
While conformance with the letter of the standards could be satisfied
by changing /usr/bin/crontab's default editor to the first "vi" in
$PATH, precedent as defined by [3] and [4] among other cases leads us
to also deliver xpg4 and xpg6 variants to allow for cherry-picking.
Several reviewers felt that this takes cherry-picking too far but
there was no consensus among the committee to break with past
precedent; a median view among the Committee is that any change to
this strategy needs to involve significant review and consideration.
.LP
.NH 2
Gratuitous Divergence Obscures The Architecture
.LP
The discussion also exposed significant divergence between our
standards compliance architecture and its implementation.  In many
cases, once a decision to "fork" a command was made, many new
non-conflicting behaviors were integrated only into the xpgN variants.
However, as a general rule, there should be no cases where a
particular command feature, option, or the like accepted by a
/usr/xpgN/bin variant should generate a syntax error when fed to the
default system (/usr/bin) variant; similarly, non-conflicting features
found in the default system variant should generally be present in any
/usr/xpgN/bin variant unless they conflict with the requirements of
the relevant standards.\**
.nr MF 1
.FS
.IP [\n*]
Whenever possible we should also attempt to head off future
unresolvable divergence by avoiding new changes to the default system
variant of a command which are known to conflict with a relevant
standard.
.FE
.LP
This divergence has created both confusion about the overall
architecture, and also substantially increases the need to cherry-pick
specific command variants in scripts.
.LP
This degree of confusion is harmful to Solaris and to our users.  When
members of the community encounter such divergence, they should file
bugs against the commands in question, and should flag those bugs with
the "missing-std-feature" keyword.
.NH 2
Examples Of Divergence
.LP
Specific examples of divergence, where options and syntax are
supported by an xpgN variant of a command and are rejected as syntax
errors by the /usr/bin variant:
.NH 3
id -u, -g, -G, -n, and -r
.IP
4521640 *id* /usr/bin/id missing options from /usr/xpg4/bin/id
.NH 3
grep -e, -f, -q, -x, -E, and -F
.IP
4843344 *grep* should have -q, -e, -f, -x, -E, and -F options
.NH 3
tail -n and possibly -c
.IP 
6231496 *tail* non-XPG4 tail could support -n and possibly -c
.NH 3
du -x
.IP 
6269516 *du* should always accept -x
.NH 3
sh's lack of support for "export env=expr", $(cmd) syntax, and other
non-conflicting POSIX syntax.\**
.nr MF 1
.FS
.IP [\n*]
One early reviewer of this opinion questioned the appropriateness of
including this point, as the existing "/bin/sh" implementation is
largely unrelated to the codebase used for the /usr/xpgN/bin shells.
This is true, and will be a significant obstacle to fixing this problem, but it
is a matter of resource allocation, not architecture.  It is also the
case that the limitations of the existing "sh" are a recurring source
of irritation to newcomers to solaris and barrier to adoption by some.
Finding the proper approach and balance here will be difficult.
.FE
.IP 
6378708 *sh* could implement non-conflicting posix syntax
.LP
This is by no means a comprehensive list.   
.LP
Fixing these bugs, and identifying other inconsistencies is outside
the scope of the case, but resulted in the advice given in section 6.2.
.LP
.NH 2
Heroic Compatibility Measures Unnecessary
.LP
A proposal was made to suggest that any potential issue of script
compatibility could be addressed by having crontab invoke "ed" if
isatty(0) returned zero and "vi" if it returned nonzero.  However, as
there was no consensus that a patch binding was otherwise compatible
with a change to the default editor spawned by the crontab command,
these heroic measures were deemed unnecessary in a change with Minor
release binding.
.NH 2
Proliferation of additional setuid commands
.LP
Subsequent to the meeting, concern was expressed regarding the
delivery of additional setuid variant commands; this concern was
underscored by prior incidents where XPG4 variants which were setuid
had security holes not found in the default system variant.
The specific problem was caused by linking with values-xpg4.o and
values-xpg6.o, exposing different interfaces in the variant executables.
.LP
The current implementation plan is to deliver three setuid
executables, none of which will be linked with values-xpg?.o,
mitigating this risk.  Whether or not any specific crontab
executable is setuid is best thought of as an implementation detail,
not any sort of Public interface.
.NH
Minority Opinion(s)
.LP
No members voted to deny; however, several members of the Committee
believe that the xpgN variants of the crontab command push variant
cherry-picking beyond its actual usefulness.
.NH
Advisory Information
.LP
.NH 2
Improve standards(5) documentation relating to cherry-picking.
.LP
The PAC should ensure that both our user-facing and our
developer-facing process documentation relating to standards-related
command variants is reviewed for clarity and approchability.
.NH 2
Repair Existing Gratuitous Divergence
.LP
Unnecessarily divergent behavior between standards-compliant and
default variants of the commands we ship in Solaris is a recurring
source of irritation, confusion, and dissatisfaction.  While each
individual instance of divergence is minor, the cumulative impact is
akin to that of a thousand paper cuts.  Many of these fixes are likely
to be small "starter" bugs appropriate for new developers, though
subtleties requiring review from experienced engineers will abound.
Engineers should be encouraged to fix these and other "irritant" bugs
as they are found.
.NH
Appendices
.NH 2
Appendix A: Technical Changes Required
.LP
None.
.NH 2
Appendix B: Technical Changes Advised
.LP
None.
.NH 2
Appendix C: Reference Material
.LP
Unless stated otherwise, path names are relative to the case
directory \*(aR/\*(cA.
.IP 1.
Amended specification.  File: final.spec
.IP 2.
crontab(1) man page.  File: final/crontab.1
.IP 3.
PSARC 1994/161 XCU4 Conformance
.IP 4.
PSARC 2000/492 Austin Group Common Revision of SUSv2 and POSIX Standards.