These are the draft minutes from this week's call. Andrew will need
to allocate the Austin-xxx document number and add the file to the
document register after he returns from vacation.
Regards,
Geoff.
----------
Minutes of the 3rd August 2017 Teleconference Austin-xxx Page 1 of 1
Submitted by Geoff Clare, The Open Group. 4th August 2017
Attendees:
Mark Ziegast, SHware Systems
Jörg Schilling, FOKUS Fraunhofer
Don Cragun, IEEE PASC OR
Richard Hansen, Google
Nick Stoughton, USENIX, ISO/IEC JTC 1/SC 22 OR
Geoff Clare, The Open Group
David Clissold, IBM
Eric Blake, Red Hat
Apologies:
Martin Rehak, Oracle, The Open Group OR
Andrew Josey, The Open Group
* General news
Don reported that he has not yet received any notification from IEEE
about the Draft 1 ballot.
Richard reported that he sent an email to IEEE (stds-...@ieee.org) about
the posix.org domain on Tuesday evening but has not heard back yet.
* Outstanding actions
( Please note that this section has been flushed to shorten the minutes -
to locate the previous set of outstanding actions, look to the minutes
from 28 Jan 2016)
Bug 0000249: Add standard support for $'...' in shell Reopened
http://austingroupbugs.net/bug_view_page.php?bug_id=249
We will return to bug 249 on a future call.
Bug 0000953: Alias expansion is under-specified Was Accepted as Marked
http://austingroupbugs.net/view.php?id=953
Richard has an action to propose new wording to discuss in a future telecon.
* Current Business
Bug 1041: Encourage implementations to include better integrity checksum,
compression and decompression utilities if possible. Accept as Marked
http://austingroupbugs.net/view.php?id=1041
This item is tagged for Issue 8.
(From bugnote 3648)
On page 2584 line 83831 section cksum, change:
The /cksum/ utility is typically used to quickly compare a suspect
file against a trusted version of the same, such as to ensure that
files transmitted over noisy media arrive intact. However, this
comparison cannot be considered cryptographically secure. The
chances of a damaged file producing the same CRC as the original are
small; deliberate deception is difficult, but probably not impossible.
to:
The /cksum/ utility is typically used to quickly compare a suspect
file against a trusted version of the same, such as to ensure that
files transmitted over noisy media arrive intact. However, this
comparison cannot be considered cryptographically secure. This
utility should be avoided whenever non-trivial requirements
(including safety and security) have to be fulfilled.
On page 2585 line 83847 section cksum, insert a new first paragraph of
RATIONALE:
The /cksum/ utility is included in this standard for reasons of
portability but is not suitable for uses where non-trivial
requirements (including safety and security) have to be fulfilled.
Implementations are encouraged to provide utilities that implement
hash and integrity checksum algorithms of higher security and to
keep up to date with developments in this area.
(From bugnote 3813)
On Page xlvi (Informative References) add the following in proper
alphabetical order:
IETF RFC 1951
DEFLATE Compressed Data Format Specification version 1.3
P. Deutsch, May 1996 ( available at
https://www.ietf.org/rfc/rfc1951.txt )
IETF RFC 1952
GZIP file format specification version 4.3
P. Deutsch, May 1996 ( available at
https://www.ietf.org/rfc/rfc1952.txt )
On Page 2602 replace the entire page (lines 88476-84515) with the following:
NAME
compress, uncompress, zcat - compress and decompress data
SYNOPSIS
<XSI><tt>compress [-fv] [-b /value/] [-g | -m /algo/] [/file/...]
compress -c [-fv] [-b /value/] [-g | -m /algo/] [/file/]
compress -d [-cfv] [/file/...]
uncompress [-cfv] [/file/...]
zcat [/file/...]</tt></XSI>
DESCRIPTION
The /compress/ utility, when the *-d* option is not specified,
shall apply the compression algorithm identified by the *-g*
option or the *-m* /algo/ option to the named files to attempt
to reduce their size without loss of information. The /compress/
utility with the *-d* option shall apply the appropriate
decompression algorithm to the named files to restore the data
to their original state.
The /uncompress/ utility shall be equivalent to <tt>compress
-d</tt>. The /zcat/ utility shall be equivalent to <tt>compress
-c -d</tt>. If multiple /file/ operands are specified, the
decompressed data from each input file shall be concatenated to
standard output.
When compressing data, unless the *-c* option is specified,
after an input file other than standard input has been
compressed, the compressed data from the input file shall be
stored in a file with the same pathname as the input file but
with an added suffix. The added suffix shall be the suffix
associated with the algorithm (see the algorithms in Table 4-X
(on page xxx)). If appending the suffix would make the size of
the last component of the output file's pathname exceed
{NAME_MAX} bytes, the command shall fail. If appending the
suffix would make the size of the pathname exceed {PATH_MAX}
bytes, the command may fail.
When decompressing data, unless the *-c* option is specified,
after an input file other than standard input has been
decompressed, the decompressed data from the input file shall be
stored in a file with the same pathname as the input file but
with the suffix associated with the algorithm removed. [OB]If
/file/ has no suffix associated with a known compression
algorithm or /file/ does not exist and does not have a
<tt>.Z</tt> suffix, /file/ shall be used as the name of the
output file, and the default suffix <tt>.Z</tt> shall be
appended to /file/ to form the input pathname.[/OB] The behavior
is unspecified if the input pathname ends with a suffix other
than the suffix associated with the algorithm used to compress
the data. When the *-c* option is specified, /file/ can have any
suffix, or no suffix, and the utility shall use /file/ as the
input file and examine the file's contents to determine which
algorithm to use to decompress the data (it is not an error if
/file/ does not have a suffix that matches the suffix associated
with the compression algorithm).
When compressing or decompressing a file other than standard
input and the *-c* option is not specified, if the invoking
process has sufficient privilege, the ownership, modes, access
time, and modification time of the output file shall match the
ownership, modes, access time, and modification time of the
input file. After the output file has been succesfully created,
the input file shall be removed if the invoking process has
sufficient privileges. If the invoking process does not have
sufficient privileges to remove the input file (for example, if
the directory has the S_ISVTX bit set) the behavior depends on
whether the *-f* option is specified: if *-f* is not specified,
the output file shall be removed, a diagnostic message shall be
written and the utility shall continue processing other files
but the final exit status shall be non-zero; if *-f* is
specified, the output file shall not be removed and it is
unspecified whether the inability to remove the input file is
treated as an error. If it is not treated as an error, a warning
message may be written to standard error.
If no /file/ operands are specified, standard input shall be
compressed or decompressed to standard output.
[OB]If an input file that is to be removed after processing has
multiple hard links, the /compress/ and /uncompress/ utilities
may write a diagnostic message to standard error and do nothing
with the file; this behavior may depend on whether the *-f*
option is specified. If a diagnostic message is written, the
final exit status shall be non-zero.[/OB]
OPTIONS
The /compress/, /uncompress/, and /zcat/ utilities shall conform
to XBD Section 12.2 (on page 216), except that Guideline 1 does
not apply to /uncompress/ since the utility name has ten letters.
The following options shall be supported:
*-b* /value/
If the compression algorithm is LZW, /value/ specifies the
maximum number of bits to use in a code. For a conforming
application, the value argument shall be:
<tt>9 <= /value/ <= 16</tt>
The implementation may allow values of greater than 16. The
default shall be 14, 15, or 16.
If the compression algorithm is DEFLATE, /value/ specifies
the compression level. For a conforming application, the
/value/ argument shall be:
<tt>1 <= /value/ <= 9</tt>
The default shall be 6.
For other algorithms, /value/ specifies
implementation-defined tuning.
*-c*
Write to standard output; the input files shall not be
changed, and no output files shall be created.
*-d*
Decompress files. When invoked with the *-d* option, the
/compress/ utility shall restore previously compressed files
to their original state.
*-f*
Force compression or decompression of /file/, even if it
does not (for compression) actually reduce the size of the
file, or if the corresponding output file already exists. If
the *-f* option is not given and the standard input is a
terminal, the user shall be prompted as to whether an
existing output file should be overwritten. If the response
is affirmative, the existing file shall be overwritten. If
the standard input is not a terminal and *-f* is not given,
/compress/ or /uncompress/ shall write a diagnostic message
to standard error, the existing file shall not be
overwritten, and the utility shall exit with a status
greater than zero. If the *-f* option is specified and an
input file other than standard input has multiple hard
links, it is implementation-defined whether the input file
is unlinked after the corresponding output file is
successfully written, or if processing of that file is
skipped and a diagnostic message is written to standard error.
*-g*
Equivalent to *-m* /gzip/
*-m* /algo/
Use the algorithm defined by /algo/ to compress the files.
The following algorithms shall be supported:
Table 4-X Compression algorithms, *-m* option-argument
values, and suffixes
Algorithm /algo/ Filename Suffix
---------------------------------------------
adaptive LZW lzw .Z
RFC1951 DEFLATE deflate .gz
Synonym for DEFLATE gzip .gz
Other implementation-defined algorithms may be supported.
If neither of the *-m* /algo/ and *-g* options is specified,
<tt>lzw</tt> shall be used as a default /algo/ value.
Specifying more than one of the mutually exclusive *-g* and
*-m* /algo/ options, or multiple *-m* /algo/ options, shall
not be considered an error. The last option specified shall
determine the behavior of the utility.
On systems not supporting the selected algorithm, the input
files shall not be changed and an exit status greater than
two shall be returned.
*Note:*
The Lempel-Ziv compression algorithm is described in the
now-expired US Patent 4464650, which was issued to
William Eastman, Abraham Lempel, Jacob Ziv, and Martin
Cohn on August 7th, 1984 and assigned to Sperry Corporation.
The Lempel-Ziv-Welch compression algorithm is described
in the now-expired US Patent 4558302, which was issued
to Terry A. Welch on December 10th, 1985 and assigned to
Sperry Corporation.
*-v*
For /compress/, write the percentage reduction of each file
to standard error. For /uncompress/, write messages to
standard error concerning the expansion of each file.
OPERANDS
The following operand shall be supported:
/file/
A pathname of a file to be compressed or decompressed. If a
/file/ is '-', the utility shall read from standard input at
that point in the sequence and write to standard output. If
more than one /file/ operand is '-', the behavior is
unspecified.
STDIN
Standard input shall be used only if no /file/ operands are
specified or if a /file/ operand is '-'.
On page 2603, L84516-84517 replace the INPUT FILES section with:
INPUT FILES
If /file/ operands are specified, the corresponding input files
contain the data to be compressed or decompressed.
On page 2603 lines 84540-84549, replace the STDOUT, STDERR, and OUTPUT
FILES sections with:
STDOUT
For the /compress/ and /uncompress/ utilities, standard output
shall be used if no /file/ operands are specified, if a /file/
operand is '−', or if the *-c* option is specified. Otherwise,
standard output shall not be used.
The /zcat/ utility shall write the decompressed data to standard
output.
STDERR
Standard error shall be used only for diagnostic and prompt
messages, the optional warning message described in DESCRIPTION,
and the output from *−v*.
OUTPUT FILES
When decompressing input files other than standard input, the
corresponding output files shall contain the decompressed input
data. When compressing input files other than standard input,
the corresponding output files shall contain the compressed
input data. If the selected /algo/ is /deflate/ or /gzip/, the
compressed output shall be in the GZIP format described in RFC
1952. For other algorithms, the compressed output file format is
implementation-defined and interchange of such files between
implementations (including access via unspecified file sharing
mechanisms) is not required by POSIX.1-20xx.
On page 2603 line 84553 (compress EXIT STATUS section), change:
The following exit values shall be returned
to:
The following exit values shall be returned for /compress/
On page 2603 line 84558 (compress EXIT STATUS section), add:
The following exit values shall be returned for /uncompress/ and /zcat/:
0 Successful completion.
>0 An error occurred.
On page 2604 L84559-L84560 replace the CONSEQUENCES OF ERRORS section with:
CONSEQUENCES OF ERRORS
If an error occurs while compressing or decompressing an input
file other than standard input, the input file shall remain
unmodified.
On page 2604 L84572-84574, replace the last paragraph of APPLICATION
USAGE with:
In addition to trying /file/ and /file/<tt>.Z</tt> when looking for
a file to decompress, some implementations of /uncompress/ and
/zcat/ also try suffixes for other known compression algorithms if
neither /file/ nor /file/<tt>.Z</tt> is found. This version of the
standard allows, but does not require this behavior. Portable
applications should always specify the full pathname (including the
suffix) of files to be decompressed.
On page 2604 lines 84577-84583 replace the RATIONALE, FUTURE DIRECTIONS,
and SEE ALSO sections with:
RATIONALE
Earlier versions of this standard limited the value of /bits/
used by conforming applications for the lzw algorithm to 14 due
to address space limitations on 16-bit architectures. Using 15
or 16 is a much more common default when using current hardware.
Earlier versions of this standard only supported LZW
compression. The standard developers noted that existing
implementations added other compression utilities, such as
/gzip/, and found it desirable to support this widespread usage.
Some implementations had extended the /compress/ utility to
support such other schemes. The standard developers generalized
this practice by the addition of the *-m* option, even though
this was not previous practice.
The /uncompress/ *-d* option is added to match undocumented
existing practice of tested implementations.
FUTURE DIRECTIONS
When decompressing a file, the requirement to add <tt>.Z</tt> to
a /file/ operand if the given pathname does not include a suffix
associated with a known compression algorithm or if /file/ does
not exist and does not already have a <tt>.Z</tt> extension is
an obsolescent feature and may be removed in a future version.
SEE ALSO
XBD Chapter 8 (on page 173), Section 12.2 (on page 216)
Replace the entire /uncompress/ page (P3337-3339) with a pointer page to
/compress/.
Replace the entire /zcat/ page (P3471-3472) with a pointer page to
/compress/.
Bug 1053: Add a "size" mode to stty(1) OPEN
http://austingroupbugs.net/view.php?id=1053
This remains open.
Next Steps
----------
The next call is on August 10th, 2017 (a Thursday)
Calls are anchored on US time. (8am Pacific)
This call will be for the regular 90 minutes.
http://austingroupbugs.net
An IRC channel will be available for the meeting
irc://irc.freenode.net/austingroupbugs
An etherpad is usually up for the meeting, with a URL using the date format as
below:
https://posix.rhansen.org/p/201x-mm-dd
username=posix password=2115756#
--
Geoff Clare <g.cl...@opengroup.org>
The Open Group, Apex Plaza, Forbury Road, Reading, RG1 1AX, England
