path: root/doc/zutils.texi

\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename zutils.info
@documentencoding ISO-8859-15
@settitle Zutils Manual
@finalout
@c %**end of header

@set UPDATED 31 December 2023
@set VERSION 1.13-rc1

@dircategory Compression
@direntry
* Zutils: (zutils).             Utilities dealing with compressed files
@end direntry


@ifnothtml
@titlepage
@title Zutils
@subtitle Utilities dealing with compressed files
@subtitle for Zutils version @value{VERSION}, @value{UPDATED}
@author by Antonio Diaz Diaz

@page
@vskip 0pt plus 1filll
@end titlepage

@contents
@end ifnothtml

@ifnottex
@node Top
@top

This manual is for Zutils (version @value{VERSION}, @value{UPDATED}).

@menu
* Introduction::        Purpose and features of zutils
* Common options::      Options common to all utilities
* Configuration::       The configuration file zutils.conf
* Zcat::                Concatenating compressed files
* Zcmp::                Comparing compressed files byte by byte
* Zdiff::               Comparing compressed files line by line
* Zgrep::               Searching inside compressed files
* Ztest::               Testing the integrity of compressed files
* Zupdate::             Recompressing files to lzip format
* Problems::            Reporting bugs
* Concept index::       Index of concepts
@end menu

@sp 1
Copyright @copyright{} 2009-2023 Antonio Diaz Diaz.

This manual is free documentation: you have unlimited permission to copy,
distribute, and modify it.
@end ifnottex


@node Introduction
@chapter Introduction
@cindex introduction

@uref{http://www.nongnu.org/zutils/zutils.html,,Zutils}
is a collection of utilities able to process any combination of
compressed and uncompressed files transparently. If any file given,
including standard input, is compressed, its decompressed content is used.
Compressed files are decompressed on the fly; no temporary files are
created. Data format is detected by its identifier string (magic bytes), not
by the file name extension. Empty files are considered uncompressed.

These utilities are not wrapper scripts but safer and more efficient C++
programs. In particular the option @option{--recursive} is very efficient in
those utilities supporting it.

@noindent
The utilities provided are @command{zcat}, @command{zcmp}, @command{zdiff},
@command{zgrep}, @command{ztest}, and @command{zupdate}.@*
The formats supported are bzip2, gzip,
@uref{http://www.nongnu.org/lzip/lzip.html,,lzip}, xz, and zstd.@*
Zutils uses external compressors. The compressor to be used for each format
is configurable at runtime.

@command{zcat}, @command{zcmp}, @command{zdiff}, and @command{zgrep} are
improved replacements for the shell scripts provided by GNU gzip.
@command{ztest} is unique to zutils. @command{zupdate} is similar to gzip's
znew.

@anchor{search-order}
When @command{zcat}, @command{zcmp}, @command{zdiff}, or @command{zgrep}
need to try compressed file names, the search order is: lzip, gzip, bzip2,
zstd, xz. (@var{file}.[lz|gz|bz2|zst|xz]).

NOTE: Bzip2 and lzip provide well-defined values of exit status, which makes
them safe to use with zutils. Gzip and xz may return ambiguous warning
values, making them less reliable back ends for zutils. Zstd currently does
not even document its exit status in its man page.
@xref{compressor-requirements}.

FORMAT NOTE 1: The option @option{--format} allows the processing of a subset
of formats in recursive mode and when trying compressed file names. For
example, use the following command to search for the string @samp{foo} in
gzip and lzip files only:
@w{@samp{zgrep foo -r --format=gz,lz somedir somefile.tar}}.

FORMAT NOTE 2: The standard POSIX compress format (.Z) is obsolete and is
only supported through gzip. For this to work, the gzip program used (for
example GNU gzip) must be able to decompress .Z files.

LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never have
been compressed. Decompressed is used to refer to data which have undergone
the process of decompression.


@node Common options
@chapter Common options
@cindex common options

The following
@uref{http://www.nongnu.org/arg-parser/manual/arg_parser_manual.html#Argument-syntax,,options}:
are available in all the utilities. Rather than writing identical
descriptions for each of the programs, they are described here. Remember to
prepend @file{./} to any file name beginning with a hyphen, or use @samp{--}.
@ifnothtml
@xref{Argument syntax,,,arg_parser}.
@end ifnothtml

@table @code
@item -h
@itemx --help
Print an informative help message describing the options and exit.
@command{zgrep} only supports the @option{--help} form of this option.

@anchor{version}
@item -V
@itemx --version
Print the version number on the standard output and exit.
This version number should be included in all bug reports.
In verbose mode, @command{zdiff} and @command{zgrep} print also the version
of the diff or grep program used respectively. At verbosity level 1 (2 for
@command{zdiff} and @command{zgrep}) or higher, print also the versions of
the compressors used (perhaps limited by option @option{--format}). (The
compressors used must support the option @option{-V} for this to work).

@item -M @var{format_list}
@itemx --format=@var{format_list}
Process only the formats listed in the comma-separated @var{format_list}.
Valid formats are @samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz}, @samp{zst},
and @samp{un} for @samp{uncompressed}, meaning "any file name without a
known extension". This option excludes files based on extension, instead of
format, because it is more efficient. The exclusion only applies to names
generated automatically (for example when adding extensions to a file name
or when operating recursively on directories). Files given in the command
line are always processed.

Each format in @var{format_list} enables file names with the following
extensions:

@multitable {bz2} {enables} {any other file name}
@item bz2 @tab enables @tab .bz2 .tbz .tbz2
@item gz  @tab enables @tab .gz .tgz .Z
@item lz  @tab enables @tab .lz .tlz
@item xz  @tab enables @tab .xz .txz
@item zst @tab enables @tab .zst .tzst
@item un  @tab enables @tab any other file name
@end multitable

@item -N
@itemx --no-rcfile
Don't read the runtime configuration file @file{zutils.conf}.

@item --bz2=@var{command}
@itemx --gz=@var{command}
@itemx --lz=@var{command}
@itemx --xz=@var{command}
@itemx --zst=@var{command}
Set program to be used as decompressor for the corresponding format.
@var{command} may include arguments. For example
@w{@option{--lz='plzip --threads=2'}}. @command{zupdate} uses @option{--lz}
for compression, not for decompression (@pxref{lz-compressor}). The name of
the program can't begin with @samp{-}. These options override the values set
in @file{zutils.conf}. The compression program used must meet three
requirements:

@anchor{compressor-requirements}
@enumerate
@item
When called with the option @option{-d} and without file names, it must read
compressed data from the standard input and produce decompressed data on the
standard output.
@item
If the option @option{-q} is passed to zutils, the compression program must
also accept it.
@item
It must return 0 if no errors occurred, and a non-zero value otherwise.
@end enumerate

@end table

Numbers given as arguments to options may be expressed in decimal,
hexadecimal, or octal (using the same syntax as integer constants in C++),
and may be followed by a multiplier and an optional @samp{B} for "byte".

Table of SI and binary prefixes (unit multipliers):

@multitable {Prefix} {kilobyte   (10^3 = 1000)} {|} {Prefix} {kibibyte  (2^10 = 1024)}
@item Prefix @tab Value               @tab | @tab Prefix @tab Value
@item k @tab kilobyte   (10^3 = 1000) @tab | @tab Ki @tab kibibyte  (2^10 = 1024)
@item M @tab megabyte   (10^6)        @tab | @tab Mi @tab mebibyte  (2^20)
@item G @tab gigabyte   (10^9)        @tab | @tab Gi @tab gibibyte  (2^30)
@item T @tab terabyte   (10^12)       @tab | @tab Ti @tab tebibyte  (2^40)
@item P @tab petabyte   (10^15)       @tab | @tab Pi @tab pebibyte  (2^50)
@item E @tab exabyte    (10^18)       @tab | @tab Ei @tab exbibyte  (2^60)
@item Z @tab zettabyte  (10^21)       @tab | @tab Zi @tab zebibyte  (2^70)
@item Y @tab yottabyte  (10^24)       @tab | @tab Yi @tab yobibyte  (2^80)
@item R @tab ronnabyte  (10^27)       @tab | @tab Ri @tab robibyte  (2^90)
@item Q @tab quettabyte (10^30)       @tab | @tab Qi @tab quebibyte (2^100)
@end multitable


@node Configuration
@chapter The configuration file 'zutils.conf'
@cindex zutils.conf

@file{zutils.conf} is the runtime configuration file for zutils. In it you
may define the compressor name and options to be used for each format.
@file{zutils.conf} is optional; you don't need to install it in order to run
zutils.

The compressors specified in the command line override those specified
in @file{zutils.conf}.

You may copy the system @file{zutils.conf} file @file{$@{sysconfdir@}/zutils.conf}
to @file{$XDG_CONFIG_HOME/zutils.conf} and customize these options as you like.
(@env{XDG_CONFIG_HOME} defaults to @file{$HOME/.config}). The file syntax is
fairly obvious (and there are further instructions in it):

@enumerate
@item
Any line beginning with @samp{#} is a comment line.
@item
Each non-comment line defines the command to be used for the corresponding
format, with the syntax:
@example
<format> = <compressor> [options]
@end example
where <format> is one of @samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz}, or
@samp{zst}.
@end enumerate


@node Zcat
@chapter Zcat
@cindex zcat

@command{zcat} copies each @var{file} argument to standard output in
sequence. If any file given is compressed, its decompressed content is
copied. If a file given does not exist, and its name does not end with one
of the known extensions, @command{zcat} tries the compressed file names
corresponding to the formats supported until one is found.
@xref{search-order}. If a file fails to decompress, @command{zcat} continues
copying the rest of the files.

If a file is specified as @samp{-}, data are read from standard input,
decompressed if needed, and sent to standard output. Data read from
standard input must be of the same type; all uncompressed or all in the
same compressed format.

If no files are specified, recursive searches examine the current working
directory, and nonrecursive searches read standard input.

The format for running @command{zcat} is:

@example
zcat [@var{options}] [@var{files}]
@end example

@noindent
Exit status is 0 if no errors occurred, 1 otherwise.

@command{zcat} supports the following options:

@table @code
@item -A
@itemx --show-all
Equivalent to @option{-vET}.

@item -b
@itemx --number-nonblank
Number all nonblank output lines, starting with 1. The line count is
unlimited.

@item -e
Equivalent to @option{-vE}.

@item -E
@itemx --show-ends
Print a @samp{$} after the end of each line.

@item -n
@itemx --number
Number all output lines, starting with 1. The line count is unlimited.

@item -O @var{format}
@itemx --force-format=@var{format}
Force the compressed format given. Valid values for @var{format} are
@samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz}, @samp{zst}, and @samp{un} for
@samp{uncompressed}. If this option is used, the files are passed to the
corresponding decompressor (or transmitted unmodified) without checking
their format, and the exact file name must be given. Other names are not
tried.

@item -q
@itemx --quiet
Quiet operation. Suppress all messages.

@item -r
@itemx --recursive
For each directory operand, read and process all files in that directory,
recursively. Follow symbolic links given in the command line, but skip
symbolic links that are encountered recursively.

@item -R
@itemx --dereference-recursive
For each directory operand, read and process all files in that directory,
recursively, following all symbolic links.

@item -s
@itemx --squeeze-blank
Replace multiple adjacent blank lines with a single blank line.

@item -t
Equivalent to @option{-vT}.

@item -T
@itemx --show-tabs
Print TAB characters as @samp{^I}.

@item -v
@itemx --show-nonprinting
Print control characters except for LF (newline) and TAB using @samp{^}
notation and precede characters larger than 127 with @samp{M-} (which
stands for "meta").

@item --verbose
Verbose mode. Show error messages. Repeating it increases the verbosity
level. @xref{version}.

@end table


@node Zcmp
@chapter Zcmp
@cindex zcmp

@command{zcmp} compares two files and, if they differ, writes to standard
output the first byte and line number where they differ. Bytes and lines are
numbered starting with 1. A hyphen @samp{-} used as a @var{file} argument
means standard input. If any file given is compressed, its decompressed
content is used. Compressed files are decompressed on the fly; no temporary
files are created.

The format for running @command{zcmp} is:

@example
zcmp [@var{options}] @var{file1} [@var{file2}]
@end example

@noindent
This compares @var{file1} to @var{file2}. The standard input is used only if
@var{file1} or @var{file2} refers to standard input. If @var{file2} is
omitted @command{zcmp} tries to compare @var{file1} with the corresponding
uncompressed file (if @var{file1} is compressed), and then with the
corresponding compressed files of the remaining formats until one is found.
@xref{search-order}.

@noindent
An exit status of 0 means no differences were found, 1 means some
differences were found, and 2 means trouble.

@command{zcmp} supports the following options:

@table @code
@item -b
@itemx --print-bytes
Print the values of the differing bytes (in octal by default) followed by
the bytes themselves in printable form. Print control bytes as a @samp{^}
followed by a letter, and precede bytes larger than 127 with @samp{M-}
(which stands for "meta").

@item -H
@itemx --hexadecimal
Print the values of the differing bytes in hexadecimal instead of octal.

@item -i @var{size}
@itemx --ignore-initial=@var{size}
Ignore any differences in the first @var{size} bytes of the input files.
Treat files with fewer than @var{size} bytes as if they were empty. If
@var{size} is in the form @samp{@var{size1}:@var{size2}}, ignore the
first @var{size1} bytes of the first input file and the first
@var{size2} bytes of the second input file.

@item -l
@itemx --list
Print the byte numbers (in decimal) and values (in octal by default) of all
differing bytes. Bytes are numbered starting with 1.

@item -n @var{count}
@itemx --bytes=@var{count}
Compare at most @var{count} input bytes.

@item -O [@var{format1}][,@var{format2}]
@itemx --force-format=[@var{format1}][,@var{format2}]
Force the compressed formats given. If @var{format1} or @var{format2} is
omitted, the corresponding format is automatically detected. Valid values
for @var{format} are @samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz},
@samp{zst}, and @samp{un} for @samp{uncompressed}. If at least one format is
specified with this option, the file is passed to the corresponding
decompressor (or transmitted unmodified) without checking its format, and
the exact file names of both @var{file1} and @var{file2} must be given.
Other names are not tried.

@item -q
@itemx --quiet
@itemx --silent
Suppress diagnostics written to standard error, even the
@w{@samp{EOF on <name_of_shorter_file>}} diagnostic. Byte differences are
still written to standard output. (@option{-q} produces no output except
byte differences).

@item -s
@itemx --script
Write nothing to standard output or standard error when files differ, not
even the @w{@samp{EOF on <name_of_shorter_file>}} diagnostic; indicate
differing files through exit status only. Diagnostic messages are still
written to standard error when an error is encountered. (@option{-s}
produces no output except error messages).

@item -v
@itemx --verbose
Verbose mode. Undoes the effect of @option{--quiet}. Further -v's increase
the verbosity level. @xref{version}.

@end table


@node Zdiff
@chapter Zdiff
@cindex zdiff

@command{zdiff} compares two files and, if they differ, writes to standard
output the differences line by line. A hyphen @samp{-} used as a @var{file}
argument means standard input. If any file given is compressed, its
decompressed content is used. @command{zdiff} is a front end to the program
diff and has the limitation that messages from diff refer to temporary file
names instead of those specified.

The format for running @command{zdiff} is:

@example
zdiff [@var{options}] @var{file1} [@var{file2}]
@end example

@noindent
This compares @var{file1} to @var{file2}. The standard input is used only if
@var{file1} or @var{file2} refers to standard input. If @var{file2} is
omitted @command{zdiff} tries to compare @var{file1} with the corresponding
uncompressed file (if @var{file1} is compressed), and then with the
corresponding compressed files of the remaining formats until one is found.
@xref{search-order}.

@noindent
An exit status of 0 means no differences were found, 1 means some
differences were found, and 2 means trouble.

@command{zdiff} supports the following options (some options only work if
the diff program used supports them):

@table @code
@item -a
@itemx --text
Treat all files as text.

@item -b
@itemx --ignore-space-change
Ignore changes in the amount of white space.

@item -B
@itemx --ignore-blank-lines
Ignore changes whose lines are all blank.

@item -c
Use the context output format.

@item -C @var{n}
@itemx --context=@var{n}
Same as -c but use @var{n} lines of context.

@item -d
@itemx --minimal
Try hard to find a smaller set of changes.

@item -E
@itemx --ignore-tab-expansion
Ignore changes due to tab expansion.

@item -i
@itemx --ignore-case
Ignore case differences. Consider uppercase and lowercase letters equivalent.

@item -O [@var{format1}][,@var{format2}]
@itemx --force-format=[@var{format1}][,@var{format2}]
Force the compressed formats given. If @var{format1} or @var{format2} is
omitted, the corresponding format is automatically detected. Valid values
for @var{format} are @samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz},
@samp{zst}, and @samp{un} for @samp{uncompressed}. If at least one format is
specified with this option, the file is passed to the corresponding
decompressor (or transmitted unmodified) without checking its format, and
the exact file names of both @var{file1} and @var{file2} must be given.
Other names are not tried.

@item -p
@itemx --show-c-function
Show which C function each change is in.

@item -q
@itemx --brief
Output only whether files differ.

@item -s
@itemx --report-identical-files
Report when two files are identical.

@item -t
@itemx --expand-tabs
Expand tabs to spaces in output.

@item -T
@itemx --initial-tab
Make tabs line up by prepending a tab.

@item -u
Use the unified output format.

@item -U @var{n}
@itemx --unified=@var{n}
Same as -u but use @var{n} lines of context.

@item -v
@itemx --verbose
When specified before @option{--version}, print the version of the diff
program used. Further -v's increase the verbosity level. @xref{version}.

@item -w
@itemx --ignore-all-space
Ignore all white space.

@item -W @var{columns}
@itemx --width=@var{columns}
Output at most the specified number of print columns per line in side by
side format.

@item -y
@itemx --side-by-side
Use the side by side output format.

@end table


@node Zgrep
@chapter Zgrep
@cindex zgrep

@command{zgrep} is a front end to the program grep that allows transparent
search on any combination of compressed and uncompressed files. If any file
given is compressed, its decompressed content is used. If a file given does
not exist, and its name does not end with one of the known extensions,
@command{zgrep} tries the compressed file names corresponding to the formats
supported until one is found. @xref{search-order}. If a file fails to
decompress, @command{zgrep} continues searching the rest of the files.

If a file is specified as @samp{-}, data are read from standard input,
decompressed if needed, and fed to grep. Data read from standard input must
be of the same type; all uncompressed or all in the same compressed format.

If no files are specified, recursive searches examine the current working
directory, and nonrecursive searches read standard input.

For efficiency reasons, @command{zgrep} does not always read all its input.
For example, the shell command @w{@samp{base64 -d foo | zgrep -q X}} can
cause @command{zgrep} to exit immediately after reading a line containing
@samp{X}, without bothering to read the rest of its input data. This in turn
can cause base64 to exit with a nonzero status because base64 cannot write
to its output pipe after @command{zgrep} exits.

The format for running @command{zgrep} is:

@example
zgrep [@var{options}] @var{pattern} [@var{files}]
@end example

@noindent
An exit status of 0 means at least one match was found, 1 means no
matches were found, and 2 means trouble.

@command{zgrep} supports the following options (Some options only work if
the grep program used supports them. Options -h, -H, -r, -R, and -Z are
managed by @command{zgrep} and not passed to grep):

@table @code
@item -a
@itemx --text
Treat all files as text.

@item -A @var{n}
@itemx --after-context=@var{n}
Print @var{n} lines of trailing context.

@item -b
@itemx --byte-offset
Print the byte offset of each line.

@item -B @var{n}
@itemx --before-context=@var{n}
Print @var{n} lines of leading context.

@item -c
@itemx --count
Only print a count of matching lines per file.

@item -C @var{n}
@itemx --context=@var{n}
Print @var{n} lines of output context.

@item --color[=@var{when}]
Show matched strings in color. @var{when} is @samp{never}, @samp{always},
or @samp{auto}.

@item -e @var{pattern}
@itemx --regexp=@var{pattern}
Use @var{pattern} as the pattern to match.

@item -E
@itemx --extended-regexp
Interpret @var{pattern} as an extended regular expression (ERE).

@item -f @var{file}
@itemx --file=@var{file}
Obtain patterns from @var{file}, one per line.@*
When searching in several files at once, command substitution can be used
with @option{-e} to read @var{file} only once, for example if @var{file} is
not a regular file:
@w{@samp{zgrep -e "$(cat @var{file})" file1.lz file2.gz}}

@item -F
@itemx --fixed-strings
Interpret @var{pattern} as a set of newline-separated strings.

@item -G
@itemx --basic-regexp
Interpret @var{pattern} as a basic regular expression (BRE). This is the
default.

@item -h
@itemx --no-filename
Suppress the prefixing of file names on output when multiple files are
searched.

@item -H
@itemx --with-filename
Print the file name for each match.

@item -i
@itemx --ignore-case
Ignore case distinctions.

@item -I
Ignore binary files.

@item -l
@itemx --files-with-matches
Only print names of files containing at least one match. Stop reading each
file on the first match.

@item -L
@itemx --files-without-match
Only print names of files not containing any matches. Stop reading each file
on the first match.@*
Note: option -L fails (prints wrong results, returns wrong status, and even
hangs) when using GNU grep versions 3.2 to 3.4 inclusive because of a wrong
change in the exit status of grep, which was reverted in GNU grep 3.5.

@item --label=@var{label}
Display input actually coming from standard input as input coming from file
@var{label}.

@item --line-buffered
Use line buffering on output. This may cause a performance penalty.

@item -m @var{n}
@itemx --max-count=@var{n}
Stop after @var{n} matches.

@item -n
@itemx --line-number
Prefix each matched line with its line number in the input file.

@item -o
@itemx --only-matching
Show only the part of matching lines that actually matches @var{pattern}.

@item -O @var{format}
@itemx --force-format=@var{format}
Force the compressed format given. Valid values for @var{format} are
@samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz}, @samp{zst}, and @samp{un} for
@samp{uncompressed}. If this option is used, the files are passed to the
corresponding decompressor (or transmitted unmodified) without checking
their format, and the exact file name must be given. Other names are not
tried.

@item -P
@itemx --perl-regexp
Interpret @var{pattern} as a Perl-compatible regular expression (PCRE).

@item -q
@itemx --quiet
@itemx --silent
Suppress all messages. Exit immediately with zero status if any match is
found, even if an error was detected.

@item -r
@itemx --recursive
For each directory operand, read and process all files in that directory,
recursively. Follow symbolic links given in the command line, but skip
symbolic links that are encountered recursively.

@item -R
@itemx --dereference-recursive
For each directory operand, read and process all files in that directory,
recursively, following all symbolic links.

@item -s
@itemx --no-messages
Suppress error messages about nonexistent or unreadable files.

@item -T
@itemx --initial-tab
Make sure that the first character of actual line content lies on a tab
stop, so that the alignment of tabs looks normal.

@item -U
@itemx --binary
Use binary I/O on platforms affected by the bug known as "text mode I/O".
(MS-DOS, MS-Windows, OS/2).

@item -v
@itemx --invert-match
Select non-matching lines.

@item --verbose
Verbose mode. Show error messages. When specified before @option{--version},
print the version of the grep program used. Repeating it increases the
verbosity level. @xref{version}.

@item -w
@itemx --word-regexp
Match only whole words.

@item -x
@itemx --line-regexp
Match only whole lines.

@item -Z
@itemx --null
Output a zero byte (the ASCII NUL character) instead of the character that
normally follows a file name. For example, @w{@samp{zgrep -lZ}} outputs a
zero byte after each file name instead of the usual newline. This option
makes the output unambiguous, even in the presence of file names containing
unusual characters like newlines.

@end table


@node Ztest
@chapter Ztest
@cindex ztest

@command{ztest} checks the integrity of the compressed files specified. It
also warns if an uncompressed file has a compressed file name extension, or
if a compressed file has a wrong compressed extension. Uncompressed files
are otherwise ignored. If a file is specified as @samp{-}, the integrity of
compressed data read from standard input is checked. Data read from
standard input must be all in the same compressed format. If a file fails to
decompress, does not exist, can't be opened, or is a terminal, @command{ztest}
continues testing the rest of the files. A final diagnostic is shown at
verbosity level 1 or higher if any file fails the test when testing multiple
files.

If no files are specified, recursive searches examine the current working
directory, and nonrecursive searches read standard input.

Bzip2, gzip, and lzip are the primary formats. Xz and zstd are optional. If
the decompressor for the xz or zstd formats is not found, the corresponding
files are ignored.

Note that error detection in the xz format is broken. First, some xz files
lack integrity information. Second, not all xz decompressors can
@uref{http://www.nongnu.org/lzip/xz_inadequate.html#fragmented,,check the integrity}
of all xz files. Third, section 2.1.1.2 'Stream Flags' of the
@uref{http://tukaani.org/xz/xz-file-format.txt,,xz format specification}
allows xz decompressors to produce garbage output without issuing any
warning. Therefore, xz files can't always be checked as reliably as files in
the other formats can.
@c We can only hope that xz is soon abandoned.

The format for running @command{ztest} is:

@example
ztest [@var{options}] [@var{files}]
@end example

@noindent
Exit status is 0 if all compressed files check OK, 1 if environmental
problems (file not found, invalid command-line options, I/O errors, etc),
2 if any compressed file is corrupt or invalid, or if any file has an
incorrect file name extension.

@command{ztest} supports the following options:

@table @code
@item -O @var{format}
@itemx --force-format=@var{format}
Force the compressed format given. Valid values for @var{format} are
@samp{bz2}, @samp{gz}, @samp{lz}, @samp{xz}, and @samp{zst}. If this option
is used, the files are passed to the corresponding decompressor without
checking their format, and any files in a format that the decompressor can't
understand fail the test.

@item -q
@itemx --quiet
Quiet operation. Suppress all messages.

@item -r
@itemx --recursive
For each directory operand, read and process all files in that directory,
recursively. Follow symbolic links given in the command line, but skip
symbolic links that are encountered recursively.

@item -R
@itemx --dereference-recursive
For each directory operand, read and process all files in that directory,
recursively, following all symbolic links.

@item -v
@itemx --verbose
Verbose mode. Show the check status for each file processed. Further -v's
increase the verbosity level. @xref{version}.

@end table


@node Zupdate
@chapter Zupdate
@cindex zupdate

@command{zupdate} recompresses files from bzip2, gzip, xz, and zstd formats
to lzip format. Each original is compared with the new file and then
deleted. Only regular files with standard file name extensions are
recompressed, other files are ignored. Compressed files are decompressed and
then recompressed on the fly; no temporary files are created. If an error
happens while recompressing a file, @command{zupdate} exits immediately
without recompressing the rest of the files. The lzip format is chosen as
destination because it is the most appropriate for long-term archiving.

If no files are specified, recursive searches examine the current working
directory, and nonrecursive searches do nothing.

If the lzip-compressed version of a file already exists, the file is skipped
unless the option @option{--force} is given. In this case, if the comparison
with the existing lzip version fails, an error is returned and the original
file is not deleted. The operation of @command{zupdate} is meant to be safe
and not cause any data loss. Therefore, existing lzip-compressed files are
never overwritten nor deleted.

Combining the options @option{--force} and @option{--keep}, as in
@w{@samp{zupdate -f -k *.gz}}, checks that there are no differences between
each pair of files in a multiformat set of files.

The names of the original files must have one of the following extensions:@*
@samp{.bz2}, @samp{.gz}, @samp{.xz}, @samp{.zst}, or @samp{.Z}, which are
recompressed to @samp{.lz};@*
@samp{.tbz}, @samp{.tbz2}, @samp{.tgz}, @samp{.txz}, or @samp{.tzst}, which
are recompressed to @samp{.tlz}.@*
Keeping the combined extensions @w{(@samp{.tgz} ---> @samp{.tlz})} may be
useful when recompressing Slackware packages, for example.

Bzip2, gzip, and lzip are the primary formats. Xz and zstd are optional. If
the decompressor for the xz or zstd formats is not found, the corresponding
files are ignored.

Recompressing a file is much like copying or moving it. Therefore
@command{zupdate} preserves the access and modification dates, permissions,
and, if you have appropriate privileges, ownership of the file just as
@w{@samp{cp -p}} does. (If the user ID or the group ID can't be duplicated,
the file permission bits S_ISUID and S_ISGID are cleared).

The format for running @command{zupdate} is:

@example
zupdate [@var{options}] [@var{files}]
@end example

@noindent
Exit status is 0 if all the compressed files were successfully recompressed
(if needed), compared, and deleted (if requested). 1 if a non-fatal error
occurred (file not found or not regular, or has invalid format, or can't be
deleted). 2 if a fatal error occurred (invalid command-line options,
compressor can't be run, or comparison fails).

@command{zupdate} supports the following options:

@table @code
@item -d @var{dir}
@itemx --destdir=@var{dir}
Write recompressed files to another directory, using @var{dir} as base
directory, instead of writing them in the same directory as the original
files. In recursive mode, this is done by replacing each directory specified
in the command line with @var{dir} to produce the recompressed file names.
For example, @w{@samp{zupdate -r -d @var{dir} ../a}} recompresses a file
named @file{../a/b/c.gz} to @file{@var{dir}/b/c.lz}. Regular files specified
in the command line are recompressed directly into @var{dir}. For example,
@w{@samp{zupdate -d @var{dir} ../a/b/c.gz}} writes the recompressed file to
@file{@var{dir}/c.lz}.

This option allows recompressing files from a read-only file system to
another place without the need to copy or link them to the destination
directory first. (Remember to use option @option{--keep} when recompressing
read-only files to avoid warnings about files that can't be deleted).

@item -e
@itemx --expand-extensions
Expand combined file name extensions; recompress @samp{.tbz}, @samp{.tbz2},
@samp{.tgz}, @samp{.txz}, and @samp{.tzst} to @samp{tar.lz}.

@item -f
@itemx --force
Don't skip a file for which a lzip-compressed version already exists.
@option{--force} compares the content of the input file with the content of
the existing lzip file and deletes the input file if both contents are
identical.

@item -i
@itemx --ignore-errors
Ignore non-fatal errors. (See exit status above).

@item -k
@itemx --keep
Keep (don't delete) the input file after comparing it with the lzip file.
Use it when recompressing files from a read-only file system. (See option
@option{--destdir} above).

@item -l
@itemx --lzip-verbose
Pass one option @option{-v} to the lzip compressor so that it shows the
compression ratio for each file processed. Using lzip 1.15 or newer, a
second @option{-l} shows the progress of compression. Use it together with
@option{-v} to see the name of the file.

@item -q
@itemx --quiet
Quiet operation. Suppress all messages.

@item -r
@itemx --recursive
For each directory operand, read and process all files in that directory,
recursively. Follow symbolic links given in the command line, but skip
symbolic links that are encountered recursively.

@item -R
@itemx --dereference-recursive
For each directory operand, read and process all files in that directory,
recursively, following all symbolic links.

@item -v
@itemx --verbose
Verbose mode. Show the files being processed. A second @option{-v} also shows
the files being ignored and increases the verbosity level. @xref{version}.

@item -0 .. -9
Set the compression level of lzip. By default @command{zupdate} passes
@option{-9} to lzip. Custom compression options can be passed to lzip with
the option @option{--lz}. For example @w{@option{--lz='lzip -9 -s64MiB'}}.

@anchor{lz-compressor}
@item --lz=@var{command}
Set compression command. @var{command} may include arguments. For example
@w{@option{--lz='plzip --threads=2'}}. The name of the program can't begin
with @samp{-}. This option overrides the value set in @file{zutils.conf}.
The compression program used does not need to implement decompression
(@pxref{compressor-requirements}), but it must implement at least the
compression level option @option{-9} and the option @w{@option{-o @var{file}}}
to write the compressed output to @var{file}.
@uref{http://www.nongnu.org/lzip/manual/tarlz_manual.html,,tarlz} meets
these requirements, and therefore can be used to recompress POSIX tar
archives by using a command like
@w{@samp{zupdate --lz='tarlz -9 -z --no-solid' archive.tar.gz}}.
@ifnothtml
@xref{Top,tarlz manual,,tarlz}.
@end ifnothtml

@end table


@node Problems
@chapter Reporting bugs
@cindex bugs
@cindex getting help

There are probably bugs in zutils. There are certainly errors and
omissions in this manual. If you report them, they will get fixed. If
you don't, no one will ever know about them and they will remain unfixed
for all eternity, if not longer.

If you find a bug in zutils, please send electronic mail to
@email{zutils-bug@@nongnu.org}. Include the version number, which you can
find by running @w{@samp{zupdate --version}}.


@node Concept index
@unnumbered Concept index

@printindex cp

@bye