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Signed-off-by: Daniel Baumann <daniel@debian.org>
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doc/tarlz.texi
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@ -6,8 +6,8 @@
@finalout
@c %**end of header
@set UPDATED 3 January 2024
@set VERSION 0.25
@set UPDATED 7 December 2024
@set VERSION 0.26
@dircategory Archiving
@direntry
@ -38,6 +38,7 @@ This manual is for Tarlz (version @value{VERSION}, @value{UPDATED}).
@menu
* Introduction:: Purpose and features of tarlz
* Invoking tarlz:: Command-line interface
* Argument syntax:: By convention, options start with a hyphen
* Portable character set:: POSIX portable filename character set
* File format:: Detailed format of the compressed archive
* Amendments to pax format:: The reasons for the differences with pax
@ -150,21 +151,22 @@ Tarlz does not use absolute file names nor file names above the current
working directory (perhaps changed by option @option{-C}). On archive creation
or appending tarlz archives the files specified, but removes from member
names any leading and trailing slashes and any file name prefixes containing
a @samp{..} component. On extraction, leading and trailing slashes are also
removed from member names, and archive members containing a @samp{..}
a @file{..} component. On extraction, leading and trailing slashes are also
removed from member names, and archive members containing a @file{..}
component in the file name are skipped. Tarlz does not follow symbolic links
during extraction; not even symbolic links replacing intermediate
directories.
On extraction and listing, tarlz removes leading @samp{./} strings from
On extraction and listing, tarlz removes leading @file{./} strings from
member names in the archive or given in the command line, so that
@w{@samp{tarlz -xf foo ./bar baz}} extracts members @samp{bar} and
@samp{./baz} from archive @samp{foo}.
@w{@samp{tarlz -xf foo ./bar baz}} extracts members @file{bar} and
@file{./baz} from archive @file{foo}.
If several compression levels or @option{--*solid} options are given, the last
setting is used. For example @w{@option{-9 --solid --uncompressed -1}} is
equivalent to @w{@option{-1 --solid}}.
@noindent
tarlz supports the following operations:
@table @code
@ -277,7 +279,7 @@ standard output (unless the option @option{--output} is used). Tarlz can be
used as compressor for GNU tar by using a command like
@w{@samp{tar -c -Hustar foo | tarlz -z -o foo.tar.lz}}. Tarlz can be used as
compressor for zupdate (zutils) by using a command like
@w{@samp{zupdate --lz="tarlz -z" foo.tar.gz}}. Note that tarlz only works
@w{@samp{zupdate --lz='tarlz -z' foo.tar.gz}}. Note that tarlz only works
reliably on archives without global headers, or with global headers whose
content can be ignored.
@ -285,10 +287,10 @@ The compression is reversible, including any garbage present after the
end-of-archive blocks. Tarlz stops parsing after the first end-of-archive
block is found, and then compresses the rest of the archive. Unless solid
compression is requested, the end-of-archive blocks are compressed in a lzip
member separated from the preceding members and from any non-zero garbage
member separated from the preceding members and from any nonzero garbage
following the end-of-archive blocks. @option{--compress} implies plzip
argument style, not tar style. Each input archive is compressed to a file
with the extension @samp{.lz} added unless the option @option{--output} is
with the extension @file{.lz} added unless the option @option{--output} is
used. When @option{--output} is used, only one input archive can be specified.
@option{-f} can't be used with @option{--compress}.
@ -308,11 +310,8 @@ and the value of LZ_API_VERSION (if defined).
@end table
tarlz supports the following
@uref{http://www.nongnu.org/arg-parser/manual/arg_parser_manual.html#Argument-syntax,,options}:
@ifnothtml
@xref{Argument syntax,,,arg_parser}.
@end ifnothtml
@noindent
tarlz supports the following options: @xref{Argument syntax}.
@table @code
@anchor{--data-size}
@ -326,17 +325,17 @@ defaults to @w{1 MiB}. @xref{Minimum archive sizes}.
@item -C @var{dir}
@itemx --directory=@var{dir}
Change to directory @var{dir}. When creating, appending, comparing, or
extracting, the position of each @option{-C} option in the command line is
extracting, the position of each option @option{-C} in the command line is
significant; it changes the current working directory for the following
@var{files} until a new @option{-C} option appears in the command line.
@option{--list} and @option{--delete} ignore any @option{-C} options
@var{files} until a new option @option{-C} appears in the command line.
@option{--list} and @option{--delete} ignore any option @option{-C}
specified. @var{dir} is relative to the then current working directory,
perhaps changed by a previous @option{-C} option.
perhaps changed by a previous option @option{-C}.
Note that a process can only have one current working directory (CWD).
Therefore multi-threading can't be used to create or decode an archive if a
@option{-C} option appears after a (relative) file name in the command line.
(All file names are made relative when decoding).
Therefore multi-threading can't be used to create or decode an archive if an
option @option{-C} appears after a (relative) file name in the command line.
(All file names are made relative by removing leading slashes when decoding).
@item -f @var{archive}
@itemx --file=@var{archive}
@ -351,7 +350,7 @@ Archive or compare the files they point to instead of the links themselves.
@item -n @var{n}
@itemx --threads=@var{n}
Set the number of (de)compression threads, overriding the system's default.
Valid values range from 0 to "as many as your system can support". A value
Valid values range from 0 to as many as your system can support. A value
of 0 disables threads entirely. If this option is not used, tarlz tries to
detect the number of processors in the system and use it as default value.
@w{@samp{tarlz --help}} shows the system's default value. See the note about
@ -391,7 +390,7 @@ tarlz also minimizes the dictionary size of the lzip members it creates,
reducing the amount of memory required for decompression.
@multitable {Level} {Dictionary size} {Match length limit}
@item Level @tab Dictionary size @tab Match length limit
@headitem Level @tab Dictionary size @tab Match length limit
@item -0 @tab 64 KiB @tab 16 bytes
@item -1 @tab 1 MiB @tab 5 bytes
@item -2 @tab 1.5 MiB @tab 6 bytes
@ -410,7 +409,7 @@ uncompressed tar archive instead. With @option{--append}, don't compress the
new members appended to the tar archive. Compressed members can't be
appended to an uncompressed archive, nor vice versa. @option{--uncompressed}
can be omitted if it can be deduced from the archive name. (An uncompressed
archive name lacks a @samp{.lz} or @samp{.tlz} extension).
archive name lacks a @file{.lz} or @file{.tlz} extension).
@item --asolid
When creating or appending to a compressed archive, use appendable solid
@ -466,11 +465,11 @@ If @var{group} is not a valid group name, it is decoded as a decimal numeric
group ID.
@item --exclude=@var{pattern}
Exclude files matching a shell pattern like @samp{*.o}. A file is considered
to match if any component of the file name matches. For example, @samp{*.o}
matches @samp{foo.o}, @samp{foo.o/bar} and @samp{foo/bar.o}. If
Exclude files matching a shell pattern like @file{*.o}. A file is considered
to match if any component of the file name matches. For example, @file{*.o}
matches @file{foo.o}, @file{foo.o/bar} and @file{foo/bar.o}. If
@var{pattern} contains a @samp{/}, it matches a corresponding @samp{/} in
the file name. For example, @samp{foo/*.o} matches @samp{foo/bar.o}.
the file name. For example, @file{foo/*.o} matches @file{foo/bar.o}.
Multiple @option{--exclude} options can be specified.
@item --ignore-ids
@ -545,6 +544,53 @@ etc), 2 to indicate a corrupt or invalid input file, 3 for an internal
consistency error (e.g., bug) which caused tarlz to panic.
@node Argument syntax
@chapter Syntax of command-line arguments
@cindex argument syntax
POSIX recommends these conventions for command-line arguments.
@itemize @bullet
@item A command-line argument is an option if it begins with a hyphen
(@samp{-}).
@item Option names are single alphanumeric characters.
@item Certain options require an argument.
@item An option and its argument may or may not appear as separate tokens.
(In other words, the whitespace separating them is optional).
Thus, @w{@option{-o foo}} and @option{-ofoo} are equivalent.
@item One or more options without arguments, followed by at most one option
that takes an argument, may follow a hyphen in a single token.
Thus, @option{-abc} is equivalent to @w{@option{-a -b -c}}.
@item Options typically precede other non-option arguments.
@item The argument @samp{--} terminates all options; any following arguments
are treated as non-option arguments, even if they begin with a hyphen.
@item A token consisting of a single hyphen character is interpreted as an
ordinary non-option argument. By convention, it is used to specify standard
input, standard output, or a file named @samp{-}.
@end itemize
@noindent
GNU adds @dfn{long options} to these conventions:
@itemize @bullet
@item A long option consists of two hyphens (@samp{--}) followed by a name
made of alphanumeric characters and hyphens. Option names are typically one
to three words long, with hyphens to separate words. Abbreviations can be
used for the long option names as long as the abbreviations are unique.
@item A long option and its argument may or may not appear as separate
tokens. In the latter case they must be separated by an equal sign @samp{=}.
Thus, @w{@option{--foo bar}} and @option{--foo=bar} are equivalent.
@end itemize
@node Portable character set
@chapter POSIX portable filename character set
@cindex portable character set
@ -587,10 +633,11 @@ represents one byte; a box like this:
represents a variable number of bytes or a fixed but large number of
bytes (for example 512).
@sp 1
@noindent
A tar.lz file consists of one or more lzip members (compressed data sets).
The members simply appear one after another in the file, with no additional
information before, between, or after them.
information before, between, or after them. Empty members (data size = 0)
are not allowed in multimember files.
Each lzip member contains one or more tar members in a simplified POSIX pax
interchange format. The only pax typeflag value supported by tarlz (in
@ -628,7 +675,7 @@ binary zeros, interpreted as an end-of-archive indicator. These EOA blocks
are either compressed in a separate lzip member or compressed along with the
tar members contained in the last lzip member. For a compressed archive to
be recognized by tarlz as appendable, the last lzip member must contain
between 512 and 32256 zeros alone (without any non-zero bytes).
between 512 and 32256 zeros alone (without any nonzero bytes).
The diagram below shows the correspondence between each tar member (formed
by one or two headers plus optional data) in the tar archive and each
@ -652,25 +699,24 @@ tar.lz
@end verbatim
@ignore
When @option{--permissive} is used, the following violations of the
archive format are allowed:@*
If several extended headers precede an ustar header, only the last
extended header takes effect. The other extended headers are ignored.
Similarly, if several records with the same keyword appear in the same
block of extended records, only the last record for the repeated keyword
takes effect. The other records for the repeated keyword are ignored.@*
A global header inserted between an extended header and an ustar header.@*
When @option{--permissive} is used, the following violations of the archive
format are allowed:@*
If several extended headers precede a ustar header, only the last extended
header takes effect. The other extended headers are ignored. Similarly, if
several records with the same keyword appear in the same block of extended
records, only the last record for the repeated keyword takes effect. The
other records for the repeated keyword are ignored.@*
A global header inserted between an extended header and a ustar header.@*
An extended header just before the end-of-archive blocks.
@end ignore
@sp 1
@section Pax header block
The pax header block is identical to the ustar header block described below
except that the typeflag has the value @samp{x} (extended). The field
@samp{size} is the size of the extended header data in bytes. Most other
fields in the pax header block are zeroed on archive creation to prevent
trouble if the archive is read by an ustar tool, and are ignored by tarlz on
trouble if the archive is read by a ustar tool, and are ignored by tarlz on
archive extraction. @xref{flawed-compat}.
Tarlz limits the size of the pax extended header data so that the whole
@ -756,14 +802,13 @@ swapping of two bytes.
At verbosity level 1 or higher tarlz prints a diagnostic for each unknown
extended header keyword found in an archive, once per keyword.
@sp 1
@section Ustar header block
The ustar header block has a length of 512 bytes and is structured as
shown in the following table. All lengths and offsets are in decimal.
shown in the following table. All lengths and offsets are in decimal:
@multitable {Field Name} {Offset} {Length (in bytes)}
@item Field Name @tab Offset @tab Length (in bytes)
@headitem Field Name @tab Offset @tab Length (in bytes)
@item name @tab 0 @tab 100
@item mode @tab 100 @tab 8
@item uid @tab 108 @tab 8
@ -901,7 +946,6 @@ In order to achieve this goal and avoid some other flaws in the pax format,
tarlz makes some changes to the variant of the pax format that it uses. This
chapter describes these changes and the concrete reasons to implement them.
@sp 1
@anchor{crc32}
@section Add a CRC of the extended records
@ -928,7 +972,6 @@ Because of the above, tarlz protects the extended records with a Cyclic
Redundancy Check (CRC) in a way compatible with standard tar tools.
@xref{key_crc32}.
@sp 1
@anchor{flawed-compat}
@section Remove flawed backward compatibility
@ -958,12 +1001,11 @@ extraction.
If an extended header is required for any reason (for example a file size of
@w{8 GiB} or larger, or a link name longer than 100 bytes), tarlz also moves
the file name to the extended records to prevent an ustar tool from trying
to extract the file or link. This also makes easier during parallel decoding
the file name to the extended records to prevent a ustar tool from trying to
extract the file or link. This also makes easier during parallel decoding
the detection of a tar member split between two lzip members at the boundary
between the extended header and the ustar header.
@sp 1
@section As simple as possible (but not simpler)
The tarlz format is mainly ustar. Extended pax headers are used only when
@ -978,7 +1020,6 @@ Global pax headers are tolerated, but not supported; they are parsed and
ignored. Some operations may not behave as expected if the archive contains
global headers.
@sp 1
@section Improve reproducibility
Pax includes by default the process ID of the pax process in the ustar name
@ -990,7 +1031,6 @@ Pax allows an extended record to have length x-1 or x if x is a power of
ten; @samp{99<97_bytes>} or @samp{100<97_bytes>}. Tarlz minimizes the length
of the record and always produces a length of x-1 in these cases.
@sp 1
@section No data in hard links
Tarlz does not allow data in hard link members. The data (if any) must be in
@ -999,7 +1039,6 @@ the names of a file are stored as hard links, the type of the file is lost.
Not allowing data in hard links also prevents invalid actions like
extracting file data for a hard link to a symbolic link or to a directory.
@sp 1
@section Avoid misconversions to/from UTF-8
There is no portable way to tell what charset a text string is coded into.
@ -1025,7 +1064,7 @@ added complication of the solidity levels.
@xref{Program design,,,plzip}.
@end ifnothtml
A grouper thread and several worker threads are created, acting the main
thread as muxer (multiplexer) thread. A "packet courier" takes care of data
thread as muxer (multiplexer) thread. A 'packet courier' takes care of data
transfers among threads and limits the maximum number of data blocks
(packets) being processed simultaneously.
@ -1074,8 +1113,8 @@ access files in the file system either to read them (diff) or write them
As misaligned tar.lz archives can't be decoded in parallel, and the
misalignment can't be detected until after decoding has started, a
"mastership request" mechanism has been designed that allows the decoding to
continue instead of signalling an error.
'mastership request' mechanism has been designed that allows the decoding to
continue instead of exiting with an error.
During parallel decoding, if a worker finds a misalignment, it requests
mastership to decode the rest of the archive. When mastership is requested,
@ -1098,12 +1137,12 @@ error be avoided.
@chapter Limitations of parallel tar decoding
@cindex parallel tar decoding
Safely decoding an arbitrary tar archive in parallel is only possible if one
decodes the headers sequentially first. For example, if a tar archive
containing another tar archive is decoded starting from some position other
than the beginning, there is no way to know if the first header found there
belongs to the outer tar archive or to the inner tar archive. Tar is a
format inherently serial; it was designed for tapes.
Safely decoding a tar archive in parallel is only possible if one decodes
the headers sequentially first. For example, if a tar archive containing
another tar archive is decoded starting from some position other than the
beginning, there is no way to know if the first header found there belongs
to the outer tar archive or to the inner tar archive. Tar is a format
inherently serial; it was designed for tapes.
The pax format is even more serial than the ustar format. Two headers need
to be decoded sequentially for each file. The extended header may even need
@ -1153,7 +1192,6 @@ the tar member data because it only decodes the part of each lzip member
corresponding to the tar member header. This is another reason why the tar
headers must provide their own integrity checking.
@sp 1
@anchor{mt-extraction}
@section Limitations of multi-threaded extraction
@ -1225,40 +1263,37 @@ data size for each level:
@cindex examples
@noindent
Example 1: Create a multimember compressed archive @samp{archive.tar.lz}
containing files @samp{a}, @samp{b} and @samp{c}.
Example 1: Create a multimember compressed archive @file{archive.tar.lz}
containing files @file{a}, @file{b} and @file{c}.
@example
tarlz -cf archive.tar.lz a b c
@end example
@sp 1
@noindent
Example 2: Append files @samp{d} and @samp{e} to the multimember compressed
archive @samp{archive.tar.lz}.
Example 2: Append files @file{d} and @file{e} to the multimember compressed
archive @file{archive.tar.lz}.
@example
tarlz -rf archive.tar.lz d e
@end example
@sp 1
@noindent
Example 3: Create a solidly compressed appendable archive
@samp{archive.tar.lz} containing files @samp{a}, @samp{b} and @samp{c}.
Then append files @samp{d} and @samp{e} to the archive.
@file{archive.tar.lz} containing files @file{a}, @file{b} and @file{c}.
Then append files @file{d} and @file{e} to the archive.
@example
tarlz --asolid -cf archive.tar.lz a b c
tarlz --asolid -rf archive.tar.lz d e
@end example
@sp 1
@noindent
Example 4: Create a compressed appendable archive containing directories
@samp{dir1}, @samp{dir2} and @samp{dir3} with a separate lzip member per
directory. Then append files @samp{a}, @samp{b}, @samp{c}, @samp{d} and
@samp{e} to the archive, all of them contained in a single lzip member.
The resulting archive @samp{archive.tar.lz} contains 5 lzip members
@file{dir1}, @file{dir2} and @file{dir3} with a separate lzip member per
directory. Then append files @file{a}, @file{b}, @file{c}, @file{d} and
@file{e} to the archive, all of them contained in a single lzip member.
The resulting archive @file{archive.tar.lz} contains 5 lzip members
(including the end-of-archive member).
@example
@ -1266,46 +1301,41 @@ tarlz --dsolid -cf archive.tar.lz dir1 dir2 dir3
tarlz --asolid -rf archive.tar.lz a b c d e
@end example
@sp 1
@noindent
Example 5: Create a solidly compressed archive @samp{archive.tar.lz}
containing files @samp{a}, @samp{b} and @samp{c}. Note that no more
Example 5: Create a solidly compressed archive @file{archive.tar.lz}
containing files @file{a}, @file{b} and @file{c}. Note that no more
files can be later appended to the archive.
@example
tarlz --solid -cf archive.tar.lz a b c
@end example
@sp 1
@noindent
Example 6: Extract all files from archive @samp{archive.tar.lz}.
Example 6: Extract all files from archive @file{archive.tar.lz}.
@example
tarlz -xf archive.tar.lz
@end example
@sp 1
@noindent
Example 7: Extract files @samp{a} and @samp{c}, and the whole tree under
directory @samp{dir1} from archive @samp{archive.tar.lz}.
Example 7: Extract files @file{a} and @file{c}, and the whole tree under
directory @file{dir1} from archive @file{archive.tar.lz}.
@example
tarlz -xf archive.tar.lz a c dir1
@end example
@sp 1
@noindent
Example 8: Copy the contents of directory @samp{sourcedir} to the directory
@samp{destdir}.
Example 8: Copy the contents of directory @file{sourcedir} to the directory
@file{destdir}.
@example
tarlz -C sourcedir --uncompressed -cf - . | tarlz -C destdir -xf -
@end example
@sp 1
@noindent
Example 9: Compress the existing POSIX archive @samp{archive.tar} and write
the output to @samp{archive.tar.lz}. Compress each member individually for
Example 9: Compress the existing POSIX archive @file{archive.tar} and write
the output to @file{archive.tar.lz}. Compress each member individually for
maximum availability. (If one member in the compressed archive gets damaged,
the other members can still be extracted).
@ -1313,19 +1343,17 @@ the other members can still be extracted).
tarlz -z --no-solid archive.tar
@end example
@sp 1
@noindent
Example 10: Compress the archive @samp{archive.tar} and write the output to
@samp{foo.tar.lz}.
Example 10: Compress the archive @file{archive.tar} and write the output to
@file{foo.tar.lz}.
@example
tarlz -z -o foo.tar.lz archive.tar
@end example
@sp 1
@noindent
Example 11: Concatenate and compress two archives @samp{archive1.tar} and
@samp{archive2.tar}, and write the output to @samp{foo.tar.lz}.
Example 11: Concatenate and compress two archives @file{archive1.tar} and
@file{archive2.tar}, and write the output to @file{foo.tar.lz}.
@example
tarlz -A archive1.tar archive2.tar | tarlz -z -o foo.tar.lz