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Zutils Manual

This manual is for Zutils (version 1.4, 29 May 2015).


Copyright © 2009-2015 Antonio Diaz Diaz.

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


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1 Introduction

Zutils is a collection of utilities able to deal with any combination of compressed and uncompressed files transparently. If any given file, 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 '--recursive' option is very efficient in those utilities supporting it.

The provided utilities are zcat, zcmp, zdiff, zgrep, ztest and zupdate.
The supported formats are bzip2, gzip, lzip and xz.
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. See compressor-requirements.

FORMAT NOTE: The '--format' option allows the processing of a subset of formats in search and recursive modes: 'zgrep foo -r --format=bz2,lz somedir'.

FORMAT NOTE 2: If the '--force-format' option is given, the files are passed to the corresponding decompressor without verifying their format, allowing for example the processing of compress'd (.Z) files with gzip: 'zcmp --force-format=gz file.Z file.lz'.

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


Numbers given as arguments to options (positions, sizes) may be followed by a multiplier and an optional 'B' for "byte".

Table of SI and binary prefixes (unit multipliers):

Prefix Value | Prefix Value
k kilobyte (10^3 = 1000) | Ki kibibyte (2^10 = 1024)
M megabyte (10^6) | Mi mebibyte (2^20)
G gigabyte (10^9) | Gi gibibyte (2^30)
T terabyte (10^12) | Ti tebibyte (2^40)
P petabyte (10^15) | Pi pebibyte (2^50)
E exabyte (10^18) | Ei exbibyte (2^60)
Z zettabyte (10^21) | Zi zebibyte (2^70)
Y yottabyte (10^24) | Yi yobibyte (2^80)


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2 Common options

The following options are available in all the utilities. Rather than writing identical descriptions for each of the programs, they are described here.

-h
--help
Print an informative help message describing the options and exit. zgrep only supports the '--help' form of this option.
-V
--version
Print the version number on the standard output and exit.
-M format_list
--format=format_list
Process only the formats listed in the comma-separated format_list. Valid formats are 'bz2', 'gz', 'lz', 'xz' and 'un' for '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 format_list enables file names with the following extensions:

bz2 enables .bz2 .tbz .tbz2
gz enables .gz .tgz
lz enables .lz .tlz
xz enables .xz .txz
un enables any other file name

-N
--no-rcfile
Don't read the runtime configuration file 'zutilsrc'.
--bz2=command
--gz=command
--lz=command
--xz=command
Set program (may include arguments) to be used as (de)compressor for the given format. The mane of the program can't begin with '-'. These options override the values set in zutilsrc. The compression program used must meet three requirements:

  1. When called with the '-d' option, it must read compressed data from the standard input and produce decompressed data on the standard output.
  2. If the '-q' option is passed to zutils, the compression program must also accept it.
  3. It must return 0 if no errors occurred, and a non-zero value otherwise.


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3 The 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. The zutilsrc file is optional; you do not need to install it in order to run zutils.

The compressors specified in the command line override those specified in the zutilsrc file.

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

  1. Any line beginning with '#' is a comment line.
  2. Each non-comment line defines the command to be used for the given format, with the syntax:
              <format> = <compressor> [options]
    

    where <format> is one of 'bz2', 'gz', 'lz' or 'xz'.


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4 Zcat

zcat copies each given file ('-' means standard input), to standard output. If any given file is compressed, its decompressed content is used. If a given file does not exist, and its name does not end with one of the known extensions, zcat tries the compressed file names corresponding to the supported formats.

If no files are specified, data is 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 compression format.

The format for running zcat is:

     zcat [options] [files]

Exit status is 0 if no errors occurred, non-zero otherwise.

zcat supports the following options:

-A
--show-all
Equivalent to '-vET'.
-b
--number-nonblank
Number all nonblank output lines, starting with 1. The line count is unlimited.
-e
Equivalent to '-vE'.
-E
--show-ends
Print a '$' after the end of each line.
-n
--number
Number all output lines, starting with 1. The line count is unlimited.
-O format
--force-format=format
Force the given compression format. Valid values for format are 'bz2', 'gz', 'lz' and 'xz'. 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.
-q
--quiet
Quiet operation. Suppress all messages.
-r
--recursive
Operate recursively on directories.
-s
--squeeze-blank
Replace multiple adjacent blank lines with a single blank line.
-t
Equivalent to '-vT'.
-T
--show-tabs
Print TAB characters as '^I'.
-v
--show-nonprinting
Print control characters except for LF (newline) and TAB using '^' notation and precede characters larger than 127 with 'M-' (which stands for "meta").
--verbose
Verbose mode. Show error messages.


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5 Zcmp

zcmp compares two files ('-' means standard input), and if they differ, tells the first byte and line number where they differ. Bytes and lines are numbered starting with 1. If any given file 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:

     zcmp [options] file1 [file2]

This compares file1 to file2. If file2 is omitted zcmp tries the following:

  1. If file1 is compressed, compares its decompressed contents with the corresponding uncompressed file (the name of file1 with the extension removed).
  2. If file1 is uncompressed, compares it with the decompressed contents of file1.[lz|bz2|gz|xz] (the first one that is found).
  3. If no suitable file is found, compares file1 with data read from standard input.

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:

-b
--print-bytes
Print the differing bytes. Print control bytes as a '^' followed by a letter, and precede bytes larger than 127 with 'M-' (which stands for "meta").
-i size
--ignore-initial=size
Ignore any differences in the first size bytes of the input files. Treat files with fewer than size bytes as if they were empty. If size is in the form 'size1,size2', ignore the first size1 bytes of the first input file and the first size2 bytes of the second input file.
-l
-v
--list
--verbose
Print the byte numbers (in decimal) and values (in octal) of all differing bytes.
-n count
--bytes=count
Compare at most count input bytes.
-O [format1][,format2]
--force-format=[format1][,format2]
Force the given compression formats. Any of format1 or format2 may be omitted and the corresponding format will be automatically detected. Valid values for format are 'bz2', 'gz', 'lz' and 'xz'. 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 file1 and file2 must be given. Other names won't be tried.
-q
-s
--quiet
--silent
Do not print anything; only return an exit status indicating whether the files differ.


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6 Zdiff

zdiff compares two files ('-' means standard input), and if they differ, shows the differences line by line. If any given file is compressed, its decompressed content is used. zdiff is a front end to the diff program and has the limitation that messages from diff refer to temporary file names instead of those specified.

The format for running zdiff is:

     zdiff [options] file1 [file2]

This compares file1 to file2. If file2 is omitted zdiff tries the following:

  1. If file1 is compressed, compares its decompressed contents with the corresponding uncompressed file (the name of file1 with the extension removed).
  2. If file1 is uncompressed, compares it with the decompressed contents of file1.[lz|bz2|gz|xz] (the first one that is found).
  3. If no suitable file is found, compares file1 with data read from standard input.

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:

-a
--text
Treat all files as text.
-b
--ignore-space-change
Ignore changes in the amount of white space.
-B
--ignore-blank-lines
Ignore changes whose lines are all blank.
-c
Use the context output format.
-C n
--context=n
Same as -c but use n lines of context.
-d
--minimal
Try hard to find a smaller set of changes.
-E
--ignore-tab-expansion
Ignore changes due to tab expansion.
-i
--ignore-case
Ignore case differences in file contents.
-O [format1][,format2]
--force-format=[format1][,format2]
Force the given compression formats. Any of format1 or format2 may be omitted and the corresponding format will be automatically detected. Valid values for format are 'bz2', 'gz', 'lz' and 'xz'. 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 file1 and file2 must be given. Other names won't be tried.
-p
--show-c-function
Show which C function each change is in.
-q
--brief
Output only whether files differ.
-s
--report-identical-files
Report when two files are identical.
-t
--expand-tabs
Expand tabs to spaces in output.
-T
--initial-tab
Make tabs line up by prepending a tab.
-u
Use the unified output format.
-U n
--unified=n
Same as -u but use n lines of context.
-w
--ignore-all-space
Ignore all white space.


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7 Zgrep

zgrep is a front end to the grep program that allows transparent search on any combination of compressed and uncompressed files. If any given file is compressed, its decompressed content is used. If a given file does not exist, and its name does not end with one of the known extensions, zgrep tries the compressed file names corresponding to the supported formats.

If no files are specified, data is 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 compression format.

The format for running zgrep is:

     zgrep [options] pattern [files]

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:

-a
--text
Treat all files as text.
-A n
--after-context=n
Print n lines of trailing context.
-b
--byte-offset
Print the byte offset of each line.
-B n
--before-context=n
Print n lines of leading context.
-c
--count
Only print a count of matching lines per file.
-C n
--context=n
Print n lines of output context.
-e pattern
--regexp=pattern
Use pattern as the pattern to match.
-E
--extended-regexp
Treat pattern as an extended regular expression.
-f file
--file=file
Obtain patterns from file, one per line.
-F
--fixed-strings
Treat pattern as a set of newline-separated strings.
-h
--no-filename
Suppress the prefixing of file names on output when multiple files are searched.
-H
--with-filename
Print the file name for each match.
-i
--ignore-case
Ignore case distinctions.
-I
Ignore binary files.
-l
--files-with-matches
Only print names of files containing at least one match.
-L
--files-without-match
Only print names of files not containing any matches.
-m n
--max-count=n
Stop after n matches.
-n
--line-number
Prefix each matched line with its line number in the input file.
-o
--only-matching
Show only the part of matching lines that actually matches pattern.
-O format
--force-format=format
Force the given compression format. Valid values for format are 'bz2', 'gz', 'lz' and 'xz'. 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.
-q
--quiet
Suppress all messages. Exit immediately with zero status if any match is found, even if an error was detected.
-r
--recursive
Operate recursively on directories.
-s
--no-messages
Suppress error messages about nonexistent or unreadable files.
-v
--invert-match
Select non-matching lines.
--verbose
Verbose mode. Show error messages.
-w
--word-regexp
Match only whole words.
-x
--line-regexp
Match only whole lines.


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8 Ztest

ztest verifies the integrity of the specified compressed files. Uncompressed files are ignored. If no files are specified, the integrity of compressed data read from standard input is verified. Data read from standard input must be all in the same compression format.

Note that some xz files lack integrity information, and therefore can't be verified as reliably as the other formats can.

The format for running ztest is:

     ztest [options] [files]

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:

-O format
--force-format=format
Force the given compression format. Valid values for format are 'bz2', 'gz', 'lz' and 'xz'. 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. For example, '--force-format=gz' can test gzipped (.gz) and compress'd (.Z) files if the compressor used is GNU gzip.
-q
--quiet
Quiet operation. Suppress all messages.
-r
--recursive
Operate recursively on directories.
-v
--verbose
Verbose mode. Show the verify status for each file processed.
Further -v's increase the verbosity level.


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9 Zupdate

zupdate recompresses files from bzip2, gzip, and xz formats to lzip format. The originals are compared with the new files 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. The lzip format is chosen as destination because it is by far the most appropriate for long-term data archiving.

If the lzip compressed version of a file already exists, the file is skipped unless the '--force' option 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 produce any data loss. Therefore, existing lzip compressed files are never overwritten nor deleted.

Combining the '--force' and '--keep' options, as in 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: '.bz2', '.tbz', '.tbz2', '.gz', '.tgz', '.xz', '.txz'. The files produced have the extensions '.lz' or '.tar.lz'.

Recompressing a file is much like copying or moving it; therefore zupdate preserves the access and modification dates, permissions, and, when possible, ownership of the file just as "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:

     zupdate [options] [files]

Exit status is 0 if all the compressed files were successfully recompressed (if needed), compared and deleted (if requested). Non-zero otherwise.

zupdate supports the following options:

-f
--force
Do not skip a file for which a lzip compressed version already exists. '--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.
-k
--keep
Keep (don't delete) the input file after comparing it with the lzip file.
-l
--lzip-verbose
Pass a '-v' option to the lzip compressor so that it shows the compression ratio for each file processed. Using lzip 1.15 and newer, a second '-l' shows the progress of compression. Use it together with '-v' to see the name of the file.
-q
--quiet
Quiet operation. Suppress all messages.
-r
--recursive
Operate recursively on directories.
-v
--verbose
Verbose mode. Show the files being processed. A second '-v' also shows the files being ignored.
-0 .. -9
Set the compression level of lzip. By default zupdate passes '-9' to lzip.


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10 Reporting bugs

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 zutils-bug@nongnu.org. Include the version number, which you can find by running zupdate --version.


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