Changes to the P1003 D4 Draft Proposed Standard

[Moderator, John Quarterman]

This article mentions some changes to the P1003.D4 draft by section,
sometimes with discussion of the motivation for the changes.
There were far too many changes to record them all, and I do not
have the minutes which have the details anyway.  Thus I am trying
here merely to mention changes which strongly affect the reader
of P1003.D4, in hopes of reducing duplicate effort.

Section 2.2, General Terms, has been expanded to include many
previously missing definitions.  There was a proposal to change the
format to be more tutorial, with definitions of specific terms embedded
in paragraphs discussing related concepts (in fact, the writeup in that
form was considered to be the text of that section for D4 instead of
what appears in the current copy, which is older).  The consensus was
that, while there is certainly a need for such tutorial material,
a standard is a reference, not a place to learn the operating system.
The result is the same general form as that of P1003.D4, though
somewhat more detailed.

Much attention has been paid to error codes throughout the document.
Many of the definitions in 2.3, Error Numbers, have been revised.

The spurious last sentence about structure elements in section 2.4
has been deleted.

Most places where the numeric values of symbolic constants were
given, such as section 2.8, Symbolic Constants, the numeric values
have been removed, and the form of the display has been changed
from C preprocessor definitions to a table.  I believe there is
an intention to give the numeric values in appendices as examples
of what they historically have been.  The main exception is section
14. Data Interchange Format, as the values of the bytes on the tape
or other interchange medium must be defined.

In section 4.2, User Identification, it was decided that there
was no need for three methods of getting the user's login name
(cuserid, getlogin, and getlogname).  Getlogname was removed,
and the writeups of the other two were redone to emphasize when
it was appropriate to use each.  Note that though the logname
function was removed, the LOGNAME environment variable was not.
These changes are different from what is in the SVID or X/OPEN
documents.

Ustat, and its containing section 7.9.1, File System Statistics,
no longer exist.  The reasoning was that only a very few programs
used it (df and ed) and it does not generalize easily to networked
file systems.  Df is not defined by the standard, and the use
of ustat in ed is not necessary and not sufficient.  Also, ustat
required the definition of a "mounted file system" which was otherwise
not in the standard (as mount and umount are not).

In section 8.3, Pipes, much work was put into producing a description
which permitted most known existing implementations while retaining
enough specificity to be useful.  There are a few areas which will
affect existing implementations, but this is more because there
already were conflicting implementations, not that P1003 wishes
to legislate one version as the better one.  A table will appear
in an appendix showing what happens with various attempts at
writing with O_NDELAY on or off, and with differing buffer sizes.
The Version 8 manual was an inspiration for some of the wording.

In section 8.6, Input and Output, a proposal to change the
nbyte arguments of read and write from type int to unsigned
failed to pass the committee, as has apparently happened many
times before.  Verbiage was added to the Errors subsections
to clarify what may happen if a negative nbyte argument is passed.

In section 8.7.3, File Record Locking, the last vestiges of references
to enforcement mode were removed.  There were only two known
implementations of enforcement mode, and the representatives of both
companies (AT&T and HP) said they had done it only because the
/usr/group standard had included it, and they would be happy to have it
removed.

Section 9.1.1, Termios, does not appear in the copy of the draft which
is currently available, but was supplied to the committee as a separate
document which I believe was considered to be part of P1003.D4.  The
subcommittee which considered it at the meeting recommended removing it
from the draft standard altogether.  The reasons for this were various,
including that the wording was too stringent in places (it would
apparently require an X.25 or TCP/IP/RS232C connection to act like an
ordinary terminal port) and too vague in others (it was not clear what
a line discipline was).  Also, there was no provision for speeds other
than the traditional ones up to 19200 baud, only one direction of
XON/XOFF protocol was supported, etc.

In the full committee, several members objected to the removal of the
termio section on the grounds that a) many of the objections to the
section were internationalization issues, and the committee had
otherwise explicitly avoided addressing such issues, and b) the draft
standard really needed a termio section, as it would risk being voted
down by the balloting committee if it lacked one.  It was speculated
that the /usr/group standard would have had more influence if it had
included a similar section.

The resolution was to put the existing termio section in an appendix,
while letting section 9.1.1 refer to the appendix, saying something
to the effect that the committee did intend to have a section similar
to the one currently in the appendix, but possibly not until after
trial use.  This prohibits anyone from specifying compliance to the
current termio section, while making the intention to include one clear.

In section 12. Passwords, there are no longer any references to text
files for the /etc/passwd or /etc/group information.  Only the getpwent
and getgrent functions are defined:  the internal storage format is
not defined.

Once again, remember that these are only my opinions, and not those
of the P1003 committee, IEEE, or anyone else.

Volume-Number: Volume 2, Number 15