\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 12 April 2022
@set VERSION 1.12-pre2

@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
* The zutilsrc file::   The zutils configuration file
* 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{} 2009-2022 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.

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

@noindent
The utilities provided are zcat, zcmp, zdiff, zgrep, ztest, and zupdate.@*
The formats supported are bzip2, gzip, lzip, xz, and zstd.@*
Zutils uses external compressors. The compressor to be used for each format
is configurable at runtime.

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

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 @samp{--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.

@sp 1
Numbers given as arguments to options (positions, sizes) 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)
@end multitable


@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.
@ifnothtml
@xref{Argument syntax,,,arg_parser}.
@end ifnothtml

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

@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, zdiff and zgrep print also the version of the diff or grep
program used respectively.

@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 @samp{zutilsrc}.

@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 (de)compressor for the corresponding format.
@var{command} may include arguments. For example
@w{@samp{--lz='plzip --threads=2'}}. The program set with @samp{--lz} is
used for both compression and decompression. The others are used only for
decompression. The name of the program can't begin with @samp{-}. These
options override the values set in @file{zutilsrc}. The compression program
used must meet three requirements:

@anchor{compressor-requirements}
@enumerate
@item
When called with the option @samp{-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 @samp{-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


@node The zutilsrc file
@chapter The zutils configuration file 'zutilsrc'
@cindex zutilsrc

@file{zutilsrc} is the runtime configuration file for zutils. In it you
may define the compressor name and options to be used for each format.
@file{zutilsrc} 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{zutilsrc}.

You may copy the system @file{zutilsrc} file @file{$@{sysconfdir@}/zutilsrc}
to @file{$HOME/.zutilsrc} and customize these options as you like. 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

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, zcat tries the compressed file names corresponding to the
formats supported. If a file fails to decompress, 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 zcat is:

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

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

zcat supports the following options:

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

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

@item -e
Equivalent to @samp{-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}, and @samp{zst}. If this option
is used, the files are passed to the corresponding decompressor without
verifying their format, and the exact file name must be given. Other names
won't be 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 @samp{-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.

@end table


@node Zcmp
@chapter Zcmp
@cindex zcmp

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 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 zcmp tries the following:

@itemize -
@item
If @var{file1} is compressed, compares its decompressed contents with
the corresponding uncompressed file (the name of @var{file1} with the
extension removed).
@item
If @var{file1} is uncompressed, compares it with the decompressed
contents of @var{file1}.[lz|bz2|gz|zst|xz] (the first one that is found).
@end itemize

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

zcmp supports the following options:

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

@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 -v
@itemx --list
@itemx --verbose
Print the byte numbers (in decimal) and values (in octal) of all
differing bytes.

@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. Any of @var{format1} or @var{format2}
may be omitted and the corresponding format will be automatically detected.
Valid values for @var{format} are @samp{bz2}, @samp{gz}, @samp{lz},
@samp{xz}, and @samp{zst}. If at least one format is specified with this
option, the file is passed to the corresponding decompressor without
verifying its format, and the exact file names of both @var{file1} and
@var{file2} must be given. Other names won't be tried.

@item -q
@itemx -s
@itemx --quiet
@itemx --silent
Don't print anything; only return an exit status indicating whether the
files differ.

@end table


@node Zdiff
@chapter Zdiff
@cindex zdiff

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. 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 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 zdiff tries the following:

@itemize -
@item
If @var{file1} is compressed, compares its decompressed contents with
the corresponding uncompressed file (the name of @var{file1} with the
extension removed).
@item
If @var{file1} is uncompressed, compares it with the decompressed
contents of @var{file1}.[lz|bz2|gz|zst|xz] (the first one that is found).
@end itemize

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

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.

@itemx -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 in file contents.

@item -O [@var{format1}][,@var{format2}]
@itemx --force-format=[@var{format1}][,@var{format2}]
Force the compressed formats given. Any of @var{format1} or @var{format2}
may be omitted and the corresponding format will be automatically detected.
Valid values for @var{format} are @samp{bz2}, @samp{gz}, @samp{lz},
@samp{xz}, and @samp{zst}. If at least one format is specified with this
option, the file is passed to the corresponding decompressor without
verifying its format, and the exact file names of both @var{file1} and
@var{file2} must be given. Other names won't be 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 @samp{--version}, print the version of the diff
program used.

@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

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, zgrep tries the compressed file names corresponding to the
formats supported. If a file fails to decompress, 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.

The format for running 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.

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
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 @samp{-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.

@item -L
@itemx --files-without-match
Only print names of files not containing any matches.@*
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}, and @samp{zst}. If this option
is used, the files are passed to the corresponding decompressor without
verifying their format, and the exact file name must be given. Other names
won't be 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 @samp{--version},
print the version of the grep program used.

@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, '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

ztest verifies the integrity of the compressed files specified.
Uncompressed files are ignored. If a file is specified as @samp{-}, the
integrity of compressed data read from standard input is verified. 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, ztest continues verifying 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,,verify 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 verified as reliably as
files in the other formats can.
@c We can only hope that xz is soon abandoned.

The format for running ztest is:

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

@noindent
The exit status is 0 if all compressed files verify OK, 1 if
environmental problems (file not found, invalid flags, I/O errors, etc),
2 if any compressed file is corrupt or invalid.

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
verifying their format, and any files in a format that the decompressor
can't understand will fail.

@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 verify status for each file processed.@*
Further -v's increase the verbosity level.

@end table


@node Zupdate
@chapter Zupdate
@cindex zupdate

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, 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 data 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 @samp{--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 zupdate is meant
to be safe and not cause any data loss. Therefore, existing lzip
compressed files are never overwritten nor deleted.

Recompressing files from a read-only file system to another place can be
done by first linking the files from the destination directory and then
compressing the links: @w{@samp{ln -s /src/foo.gz . && zupdate foo.gz}}

Combining the options @samp{--force} and @samp{--keep}, as in
@w{@samp{zupdate -f -k *.gz}}, verifies 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 (@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 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 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 (compressor can't be run, or
comparison fails).

zupdate supports the following options:

@table @code
@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.
@samp{--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.

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

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

@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
