Linux From Scratch .info files

This is tar.info, produced by makeinfo version 4.7 from tar.texi.

This manual is for GNU `tar' (version 1.15.1, 18 December 2004),
which creates and extracts files from archives.

Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.1 or any later version published by the Free Software
Foundation; with the Invariant Sections being "GNU General Public
License", with the Front-Cover Texts being "A GNU Manual," and
with the Back-Cover Texts as in (a) below. A copy of the license
is included in the section entitled "GNU Free Documentation
License".

(a) The FSF's Back-Cover Text is: "You are free to copy and modify
this GNU Manual. Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom."

INFO-DIR-SECTION Archiving
START-INFO-DIR-ENTRY
* Tar: (tar). Making tape (or disk) archives.
END-INFO-DIR-ENTRY

INFO-DIR-SECTION Individual utilities
START-INFO-DIR-ENTRY
* tar: (tar)tar invocation. Invoking GNU `tar'.
END-INFO-DIR-ENTRY

File: tar.info, Node: Top, Next: Introduction, Up: (dir)

GNU tar: an archiver tool
*************************

This manual is for GNU `tar' (version 1.15.1, 18 December 2004), which
creates and extracts files from archives.

(a) The FSF's Back-Cover Text is: "You are free to copy and modify
this GNU Manual. Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom."

The first part of this master menu lists the major nodes in this Info
document. The rest of the menu lists all the lower level nodes.

* Menu:

* Introduction::
* Tutorial::
* tar invocation::
* operations::
* Backups::
* Choosing::
* Date input formats::
* Formats::
* Media::
* Free Software Needs Free Documentation::
* Copying This Manual::
* Index::

--- The Detailed Node Listing ---

Introduction

* Book Contents:: What this Book Contains
* Definitions:: Some Definitions
* What tar Does:: What `tar' Does
* Naming tar Archives:: How `tar' Archives are Named
* Current status:: Current development status of GNU `tar'
* Authors:: GNU `tar' Authors
* Reports:: Reporting bugs or suggestions

Tutorial Introduction to `tar'

* assumptions::
* stylistic conventions::
* basic tar options:: Basic `tar' Operations and Options
* frequent operations::
* Two Frequent Options::
* create:: How to Create Archives
* list:: How to List Archives
* extract:: How to Extract Members from an Archive
* going further::

Two Frequently Used Options

* file tutorial::
* verbose tutorial::
* help tutorial::

How to Create Archives

* prepare for examples::
* Creating the archive::
* create verbose::
* short create::
* create dir::

How to List Archives

* list dir::

How to Extract Members from an Archive

* extracting archives::
* extracting files::
* extract dir::
* failing commands::

Invoking GNU `tar'

* Synopsis::
* using tar options::
* Styles::
* All Options::
* help::
* verbose::
* interactive::

The Three Option Styles

* Mnemonic Options:: Mnemonic Option Style
* Short Options:: Short Option Style
* Old Options:: Old Option Style
* Mixing:: Mixing Option Styles

All `tar' Options

* Operation Summary::
* Option Summary::
* Short Option Summary::

GNU `tar' Operations

* Basic tar::
* Advanced tar::
* create options::
* extract options::
* backup::
* Applications::
* looking ahead::

Advanced GNU `tar' Operations

* Operations::
* append::
* update::
* concatenate::
* delete::
* compare::

How to Add Files to Existing Archives: `--append'

* appending files:: Appending Files to an Archive
* multiple::

Updating an Archive

* how to update::

Options Used by `--create'

* Ignore Failed Read::

Options Used by `--extract'

* Reading:: Options to Help Read Archives
* Writing:: Changing How `tar' Writes Files
* Scarce:: Coping with Scarce Resources

Options to Help Read Archives

* read full records::
* Ignore Zeros::

Changing How `tar' Writes Files

* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
* Modification Times::
* Setting Access Permissions::
* Writing to Standard Output::
* remove files::

Coping with Scarce Resources

* Starting File::
* Same Order::

Performing Backups and Restoring Files

* Full Dumps:: Using `tar' to Perform Full Dumps
* Inc Dumps:: Using `tar' to Perform Incremental Dumps
* incremental and listed-incremental:: The Incremental Options
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Backups:: Using the Backup Scripts
* Scripted Restoration:: Using the Restore Script

Setting Parameters for Backups and Restoration

* General-Purpose Variables::
* Magnetic Tape Control::
* User Hooks::
* backup-specs example:: An Example Text of `Backup-specs'

Choosing Files and Names for `tar'

* file:: Choosing the Archive's Name
* Selecting Archive Members::
* files:: Reading Names from a File
* exclude:: Excluding Some Files
* Wildcards::
* after:: Operating Only on New Files
* recurse:: Descending into Directories
* one:: Crossing Filesystem Boundaries

Reading Names from a File

* nul::

Excluding Some Files

* controlling pattern-patching with exclude::
* problems with exclude::

Crossing Filesystem Boundaries

* directory:: Changing Directory
* absolute:: Absolute File Names

Date input formats

* General date syntax:: Common rules.
* Calendar date items:: 19 Dec 1994.
* Time of day items:: 9:20pm.
* Time zone items:: EST, PDT, GMT, ...
* Day of week items:: Monday and others.
* Relative items in date strings:: next tuesday, 2 years ago.
* Pure numbers in date strings:: 19931219, 1440.
* Seconds since the Epoch:: @1078100502.
* Authors of get_date:: Bellovin, Eggert, Salz, Berets, et al.

Controlling the Archive Format

* Portability:: Making `tar' Archives More Portable
* Compression:: Using Less Space through Compression
* Attributes:: Handling File Attributes
* Standard:: The Standard Format
* Extensions:: GNU Extensions to the Archive Format
* cpio:: Comparison of `tar' and `cpio'

Making `tar' Archives More Portable

* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
* posix:: POSIX archives
* Checksumming:: Checksumming Problems
* Large or Negative Values:: Large files, negative time stamps, etc.

Using Less Space through Compression

* gzip:: Creating and Reading Compressed Archives
* sparse:: Archiving Sparse Files

Tapes and Other Archive Media

* Device:: Device selection and switching
* Remote Tape Server::
* Common Problems and Solutions::
* Blocking:: Blocking
* Many:: Many archives on one tape
* Using Multiple Tapes:: Using Multiple Tapes
* label:: Including a Label in the Archive
* verify::
* Write Protection::

Blocking

* Format Variations:: Format Variations
* Blocking Factor:: The Blocking Factor of an Archive

Many Archives on One Tape

* Tape Positioning:: Tape Positions and Tape Marks
* mt:: The `mt' Utility

Using Multiple Tapes

* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files

Copying This Manual

* GNU Free Documentation License:: License for copying this manual

File: tar.info, Node: Introduction, Next: Tutorial, Prev: Top, Up: Top

1 Introduction
**************

GNU `tar' creates and manipulates "archives" which are actually
collections of many other files; the program provides users with an
organized and systematic method for controlling a large amount of data.
The name "tar" originally came from the phrase "Tape ARchive", but
archives need not (and these days, typically do not) reside on tapes.

* Menu:

File: tar.info, Node: Book Contents, Next: Definitions, Up: Introduction

1.1 What this Book Contains
===========================

The first part of this chapter introduces you to various terms that will
recur throughout the book. It also tells you who has worked on GNU
`tar' and its documentation, and where you should send bug reports or
comments.

The second chapter is a tutorial (*note Tutorial::) which provides a
gentle introduction for people who are new to using `tar'. It is meant
to be self contained, not requiring any reading from subsequent
chapters to make sense. It moves from topic to topic in a logical,
progressive order, building on information already explained.

Although the tutorial is paced and structured to allow beginners to
learn how to use `tar', it is not intended solely for beginners. The
tutorial explains how to use the three most frequently used operations
(`create', `list', and `extract') as well as two frequently used
options (`file' and `verbose'). The other chapters do not refer to the
tutorial frequently; however, if a section discusses something which is
a complex variant of a basic concept, there may be a cross reference to
that basic concept. (The entire book, including the tutorial, assumes
that the reader understands some basic concepts of using a Unix-type
operating system; *note Tutorial::.)

The third chapter presents the remaining five operations, and
information about using `tar' options and option syntax.

The other chapters are meant to be used as a reference. Each
chapter presents everything that needs to be said about a specific
topic.

One of the chapters (*note Date input formats::) exists in its
entirety in other GNU manuals, and is mostly self-contained. In
addition, one section of this manual (*note Standard::) contains a big
quote which is taken directly from `tar' sources.

In general, we give both long and short (abbreviated) option names
at least once in each section where the relevant option is covered, so
that novice readers will become familiar with both styles. (A few
options have no short versions, and the relevant sections will indicate
this.)

File: tar.info, Node: Definitions, Next: What tar Does, Prev: Book Contents, Up: Introduction

1.2 Some Definitions
====================

The `tar' program is used to create and manipulate `tar' archives. An
"archive" is a single file which contains the contents of many files,
while still identifying the names of the files, their owner(s), and so
forth. (In addition, archives record access permissions, user and
group, size in bytes, and last modification time. Some archives also
record the file names in each archived directory, as well as other file
and directory information.) You can use `tar' to "create" a new
archive in a specified directory.

The files inside an archive are called "members". Within this
manual, we use the term "file" to refer only to files accessible in the
normal ways (by `ls', `cat', and so forth), and the term "member" to
refer only to the members of an archive. Similarly, a "file name" is
the name of a file, as it resides in the filesystem, and a "member
name" is the name of an archive member within the archive.

The term "extraction" refers to the process of copying an archive
member (or multiple members) into a file in the filesystem. Extracting
all the members of an archive is often called "extracting the archive".
The term "unpack" can also be used to refer to the extraction of many
or all the members of an archive. Extracting an archive does not
destroy the archive's structure, just as creating an archive does not
destroy the copies of the files that exist outside of the archive. You
may also "list" the members in a given archive (this is often thought
of as "printing" them to the standard output, or the command line), or
"append" members to a pre-existing archive. All of these operations
can be performed using `tar'.

File: tar.info, Node: What tar Does, Next: Naming tar Archives, Prev: Definitions, Up: Introduction

1.3 What `tar' Does
===================

The `tar' program provides the ability to create `tar' archives, as
well as various other kinds of manipulation. For example, you can use
`tar' on previously created archives to extract files, to store
additional files, or to update or list files which were already stored.

Initially, `tar' archives were used to store files conveniently on
magnetic tape. The name `tar' comes from this use; it stands for
`t'ape `ar'chiver. Despite the utility's name, `tar' can direct its
output to available devices, files, or other programs (using pipes).
`tar' may even access remote devices or files (as archives).

You can use `tar' archives in many ways. We want to stress a few of
them: storage, backup, and transportation.

Storage
Often, `tar' archives are used to store related files for
convenient file transfer over a network. For example, the GNU
Project distributes its software bundled into `tar' archives, so
that all the files relating to a particular program (or set of
related programs) can be transferred as a single unit.

A magnetic tape can store several files in sequence. However, the
tape has no names for these files; it only knows their relative
position on the tape. One way to store several files on one tape
and retain their names is by creating a `tar' archive. Even when
the basic transfer mechanism can keep track of names, as FTP can,
the nuisance of handling multiple files, directories, and multiple
links makes `tar' archives useful.

Archive files are also used for long-term storage. You can think
of this as transportation from the present into the future. (It
is a science-fiction idiom that you can move through time as well
as in space; the idea here is that `tar' can be used to move
archives in all dimensions, even time!)

Backup
Because the archive created by `tar' is capable of preserving file
information and directory structure, `tar' is commonly used for
performing full and incremental backups of disks. A backup puts a
collection of files (possibly pertaining to many users and
projects) together on a disk or a tape. This guards against
accidental destruction of the information in those files. GNU
`tar' has special features that allow it to be used to make
incremental and full dumps of all the files in a filesystem.

Transportation
You can create an archive on one system, transfer it to another
system, and extract the contents there. This allows you to
transport a group of files from one system to another.

File: tar.info, Node: Naming tar Archives, Next: Current status, Prev: What tar Does, Up: Introduction

1.4 How `tar' Archives are Named
================================

Conventionally, `tar' archives are given names ending with `.tar'.
This is not necessary for `tar' to operate properly, but this manual
follows that convention in order to accustom readers to it and to make
examples more clear.

Often, people refer to `tar' archives as "`tar' files," and archive
members as "files" or "entries". For people familiar with the
operation of `tar', this causes no difficulty. However, in this
manual, we consistently refer to "archives" and "archive members" to
make learning to use `tar' easier for novice users.

File: tar.info, Node: Current status, Next: Authors, Prev: Naming tar Archives, Up: Introduction

1.5 Current development status of GNU `tar'
===========================================

GNU `tar' is currently in the process of active development, whose
primary aims are:

* Improve compatibility between GNU `tar' and other `tar'
implementations.

* Switch to using POSIX archives.

* Revise sparse file handling and multiple volume processing.

* Merge with the GNU `paxutils' project.

Some of these aims are already attained, while others are still
being worked upon. From the point of view of an end user, the following
issues need special mentioning:

Use of short option `-o'.
Earlier versions of GNU `tar' understood `-o' command line option
as a synonym for `--old-archive'.

GNU `tar' starting from version 1.13.90 understands this option as
a synonym for `--no-same-owner'. This is compatible with UNIX98
`tar' implementations.

However, to facilitate transition, `-o' option retains its old
semantics when it is used with one of archive-creation commands.
Users are encouraged to use `--format=oldgnu' instead.

It is especially important, since versions of GNU Automake up to
and including 1.8.4 invoke tar with this option to produce
distribution tarballs. *Note v7: Formats, for the detailed
discussion of this issue and its implications.

Future versions of GNU `tar' will understand `-o' only as a
synonym for `--no-same-owner'.

Use of short option `-l'
Earlier versions of GNU `tar' understood `-l' option as a synonym
for `--one-file-system'. Such usage is deprecated. For
compatibility with other implementations future versions of GNU
`tar' will understand this option as a synonym for `--check-links'.

Use of options `--portability' and `--old-archive'
These options are deprecated. Please use `--format=v7' instead.

Use of option `--posix'
This option is deprecated. Please use `--format=posix' instead.

File: tar.info, Node: Authors, Next: Reports, Prev: Current status, Up: Introduction

1.6 GNU `tar' Authors
=====================

GNU `tar' was originally written by John Gilmore, and modified by many
people. The GNU enhancements were written by Jay Fenlason, then Joy
Kendall, and the whole package has been further maintained by Thomas
Bushnell, n/BSG, Franc,ois Pinard, Paul Eggert, and finally Sergey
Poznyakoff with the help of numerous and kind users.

We wish to stress that `tar' is a collective work, and owes much to
all those people who reported problems, offered solutions and other
insights, or shared their thoughts and suggestions. An impressive, yet
partial list of those contributors can be found in the `THANKS' file
from the GNU `tar' distribution.

Jay Fenlason put together a draft of a GNU `tar' manual, borrowing
notes from the original man page from John Gilmore. This was withdrawn
in version 1.11. Thomas Bushnell, n/BSG and Amy Gorin worked on a
tutorial and manual for GNU `tar'. Franc,ois Pinard put version 1.11.8
of the manual together by taking information from all these sources and
merging them. Melissa Weisshaus finally edited and redesigned the book
to create version 1.12.

For version 1.12, Daniel Hagerty contributed a great deal of
technical consulting. In particular, he is the primary author of *Note
Backups::.

In July, 2003 GNU `tar' was put on CVS at savannah.gnu.org (see
`http://savannah.gnu.org/projects/tar'), and active development and
maintenance work has started again. Currently GNU `tar' is being
maintained by Paul Eggert, Sergey Poznyakoff and Jeff Bailey.

Support for POSIX archives was added by Sergey Poznyakoff.

File: tar.info, Node: Reports, Prev: Authors, Up: Introduction

1.7 Reporting bugs or suggestions
=================================

If you find problems or have suggestions about this program or manual,
please report them to `bug-tar@gnu.org'.

When reporting a bug, please be sure to include as much detail as
possible, in order to reproduce it. .

File: tar.info, Node: Tutorial, Next: tar invocation, Prev: Introduction, Up: Top

2 Tutorial Introduction to `tar'
********************************

This chapter guides you through some basic examples of three `tar'
operations: `--create', `--list', and `--extract'. If you already know
how to use some other version of `tar', then you may not need to read
this chapter. This chapter omits most complicated details about how
`tar' works.

* Menu:

File: tar.info, Node: assumptions, Next: stylistic conventions, Up: Tutorial

2.1 Assumptions this Tutorial Makes
===================================

This chapter is paced to allow beginners to learn about `tar' slowly.
At the same time, we will try to cover all the basic aspects of these
three operations. In order to accomplish both of these tasks, we have
made certain assumptions about your knowledge before reading this
manual, and the hardware you will be using:

* Before you start to work through this tutorial, you should
understand what the terms "archive" and "archive member" mean
(*note Definitions::). In addition, you should understand
something about how Unix-type operating systems work, and you
should know how to use some basic utilities. For example, you
should know how to create, list, copy, rename, edit, and delete
files and directories; how to change between directories; and how
to figure out where you are in the filesystem. You should have
some basic understanding of directory structure and how files are
named according to which directory they are in. You should
understand concepts such as standard output and standard input,
what various definitions of the term "argument" mean, and the
differences between relative and absolute path names.

* This manual assumes that you are working from your own home
directory (unless we state otherwise). In this tutorial, you will
create a directory to practice `tar' commands in. When we show
path names, we will assume that those paths are relative to your
home directory. For example, my home directory path is
`/home/fsf/melissa'. All of my examples are in a subdirectory of
the directory named by that path name; the subdirectory is called
`practice'.

* In general, we show examples of archives which exist on (or can be
written to, or worked with from) a directory on a hard disk. In
most cases, you could write those archives to, or work with them
on any other device, such as a tape drive. However, some of the
later examples in the tutorial and next chapter will not work on
tape drives. Additionally, working with tapes is much more
complicated than working with hard disks. For these reasons, the
tutorial does not cover working with tape drives. *Note Media::,
for complete information on using `tar' archives with tape drives.

File: tar.info, Node: stylistic conventions, Next: basic tar options, Prev: assumptions, Up: Tutorial

2.2 Stylistic Conventions
=========================

In the examples, `$' represents a typical shell prompt. It precedes
lines you should type; to make this more clear, those lines are shown
in `this font', as opposed to lines which represent the computer's
response; those lines are shown in `this font', or sometimes `like
this'.

File: tar.info, Node: basic tar options, Next: frequent operations, Prev: stylistic conventions, Up: Tutorial

2.3 Basic `tar' Operations and Options
======================================

`tar' can take a wide variety of arguments which specify and define the
actions it will have on the particular set of files or the archive.
The main types of arguments to `tar' fall into one of two classes:
operations, and options.

Some arguments fall into a class called "operations"; exactly one of
these is both allowed and required for any instance of using `tar'; you
may _not_ specify more than one. People sometimes speak of "operating
modes". You are in a particular operating mode when you have specified
the operation which specifies it; there are eight operations in total,
and thus there are eight operating modes.

The other arguments fall into the class known as "options". You are
not required to specify any options, and you are allowed to specify more
than one at a time (depending on the way you are using `tar' at that
time). Some options are used so frequently, and are so useful for
helping you type commands more carefully that they are effectively
"required". We will discuss them in this chapter.

You can write most of the `tar' operations and options in any of
three forms: long (mnemonic) form, short form, and old style. Some of
the operations and options have no short or "old" forms; however, the
operations and options which we will cover in this tutorial have
corresponding abbreviations. We will indicate those abbreviations
appropriately to get you used to seeing them. (Note that the "old
style" option forms exist in GNU `tar' for compatibility with Unix
`tar'. We present a full discussion of this way of writing options and
operations appears in *Note Old Options::, and we discuss the other two
styles of writing options in *Note Mnemonic Options::, and *Note Short
Options::.)

In the examples and in the text of this tutorial, we usually use the
long forms of operations and options; but the "short" forms produce the
same result and can make typing long `tar' commands easier. For
example, instead of typing

tar --create --verbose --file=afiles.tar apple angst aspic

you can type
tar -c -v -f afiles.tar apple angst aspic

or even
tar -cvf afiles.tar apple angst aspic

For more information on option syntax, see *Note Advanced tar::. In
discussions in the text, when we name an option by its long form, we
also give the corresponding short option in parentheses.

The term, "option", can be confusing at times, since "operations"
are often lumped in with the actual, _optional_ "options" in certain
general class statements. For example, we just talked about "short and
long forms of options and operations". However, experienced `tar'
users often refer to these by shorthand terms such as, "short and long
options". This term assumes that the "operations" are included, also.
Context will help you determine which definition of "options" to use.

Similarly, the term "command" can be confusing, as it is often used
in two different ways. People sometimes refer to `tar' "commands". A
`tar' "command" is the entire command line of user input which tells
`tar' what to do -- including the operation, options, and any arguments
(file names, pipes, other commands, etc). However, you will also
sometimes hear the term "the `tar' command". When the word "command"
is used specifically like this, a person is usually referring to the
`tar' _operation_, not the whole line. Again, use context to figure
out which of the meanings the speaker intends.

File: tar.info, Node: frequent operations, Next: Two Frequent Options, Prev: basic tar options, Up: Tutorial

2.4 The Three Most Frequently Used Operations
=============================================

Here are the three most frequently used operations (both short and long
forms), as well as a brief description of their meanings. The rest of
this chapter will cover how to use these operations in detail. We will
present the rest of the operations in the next chapter.

`--create'
`-c'
Create a new `tar' archive.

`--list'
`-t'
List the contents of an archive.

`--extract'
`-x'
Extract one or more members from an archive.

File: tar.info, Node: Two Frequent Options, Next: create, Prev: frequent operations, Up: Tutorial

2.5 Two Frequently Used Options
===============================

To understand how to run `tar' in the three operating modes listed
previously, you also need to understand how to use two of the options to
`tar': `--file' (which takes an archive file as an argument) and
`--verbose'. (You are usually not _required_ to specify either of
these options when you run `tar', but they can be very useful in making
things more clear and helping you avoid errors.)

* Menu:

* file tutorial::
* verbose tutorial::
* help tutorial::

File: tar.info, Node: file tutorial, Next: verbose tutorial, Up: Two Frequent Options

The `--file' Option
-------------------

`--file=ARCHIVE-NAME'
`-f ARCHIVE-NAME'
Specify the name of an archive file.

You can specify an argument for the `--file=ARCHIVE-NAME' (`-f
ARCHIVE-NAME') option whenever you use `tar'; this option determines
the name of the archive file that `tar' will work on.

If you don't specify this argument, then `tar' will use a default,
usually some physical tape drive attached to your machine. If there is
no tape drive attached, or the default is not meaningful, then `tar'
will print an error message. The error message might look roughly like
one of the following:

tar: can't open /dev/rmt8 : No such device or address
tar: can't open /dev/rsmt0 : I/O error

To avoid confusion, we recommend that you always specify an archive file
name by using `--file=ARCHIVE-NAME' (`-f ARCHIVE-NAME') when writing
your `tar' commands. For more information on using the
`--file=ARCHIVE-NAME' (`-f ARCHIVE-NAME') option, see *Note file::.

File: tar.info, Node: verbose tutorial, Next: help tutorial, Prev: file tutorial, Up: Two Frequent Options

The `--verbose' Option
----------------------

`--verbose'
`-v'
Show the files being worked on as `tar' is running.

`--verbose' (`-v') shows details about the results of running `tar'.
This can be especially useful when the results might not be obvious.
For example, if you want to see the progress of `tar' as it writes
files into the archive, you can use the `--verbose' option. In the
beginning, you may find it useful to use `--verbose' at all times; when
you are more accustomed to `tar', you will likely want to use it at
certain times but not at others. We will use `--verbose' at times to
help make something clear, and we will give many examples both using
and not using `--verbose' to show the differences.

Sometimes, a single instance of `--verbose' on the command line will
show a full, `ls' style listing of an archive or files, giving sizes,
owners, and similar information. Other times, `--verbose' will only
show files or members that the particular operation is operating on at
the time. In the latter case, you can use `--verbose' twice in a
command to get a listing such as that in the former case. For example,
instead of saying

tar -cvf afiles.tar apple angst aspic

above, you might say

tar -cvvf afiles.tar apple angst aspic

This works equally well using short or long forms of options. Using
long forms, you would simply write out the mnemonic form of the option
twice, like this:

$ tar --create --verbose --verbose ...

Note that you must double the hyphens properly each time.

Later in the tutorial, we will give examples using
`--verbose --verbose'.

File: tar.info, Node: help tutorial, Prev: verbose tutorial, Up: Two Frequent Options

Getting Help: Using the `--help' Option
---------------------------------------

`--help'
The `--help' option to `tar' prints out a very brief list of all
operations and option available for the current version of `tar'
available on your system.

File: tar.info, Node: create, Next: list, Prev: Two Frequent Options, Up: Tutorial

2.6 How to Create Archives
==========================

_(This message will disappear, once this node revised.)_

One of the basic operations of `tar' is `--create' (`-c'), which you
use to create a `tar' archive. We will explain `--create' first
because, in order to learn about the other operations, you will find it
useful to have an archive available to practice on.

To make this easier, in this section you will first create a
directory containing three files. Then, we will show you how to create
an _archive_ (inside the new directory). Both the directory, and the
archive are specifically for you to practice on. The rest of this
chapter and the next chapter will show many examples using this
directory and the files you will create: some of those files may be
other directories and other archives.

The three files you will archive in this example are called `blues',
`folk', and `jazz'. The archive is called `collection.tar'.

This section will proceed slowly, detailing how to use `--create' in
`verbose' mode, and showing examples using both short and long forms.
In the rest of the tutorial, and in the examples in the next chapter,
we will proceed at a slightly quicker pace. This section moves more
slowly to allow beginning users to understand how `tar' works.

* Menu:

* prepare for examples::
* Creating the archive::
* create verbose::
* short create::
* create dir::

File: tar.info, Node: prepare for examples, Next: Creating the archive, Up: create

2.6.1 Preparing a Practice Directory for Examples
-------------------------------------------------

To follow along with this and future examples, create a new directory
called `practice' containing files called `blues', `folk' and `jazz'.
The files can contain any information you like: ideally, they should
contain information which relates to their names, and be of different
lengths. Our examples assume that `practice' is a subdirectory of your
home directory.

Now `cd' to the directory named `practice'; `practice' is now your
"working directory". (_Please note_: Although the full path name of
this directory is `/HOMEDIR/practice', in our examples we will refer to
this directory as `practice'; the HOMEDIR is presumed.

In general, you should check that the files to be archived exist
where you think they do (in the working directory) by running `ls'.
Because you just created the directory and the files and have changed to
that directory, you probably don't need to do that this time.

It is very important to make sure there isn't already a file in the
working directory with the archive name you intend to use (in this case,
`collection.tar'), or that you don't care about its contents. Whenever
you use `create', `tar' will erase the current contents of the file
named by `--file=ARCHIVE-NAME' (`-f ARCHIVE-NAME') if it exists. `tar'
will not tell you if you are about to overwrite an archive unless you
specify an option which does this. To add files to an existing
archive, you need to use a different option, such as `--append' (`-r');
see *Note append:: for information on how to do this.

File: tar.info, Node: Creating the archive, Next: create verbose, Prev: prepare for examples, Up: create

2.6.2 Creating the Archive
--------------------------

To place the files `blues', `folk', and `jazz' into an archive named
`collection.tar', use the following command:

$ tar --create --file=collection.tar blues folk jazz

The order of the arguments is not very important, _when using long
option forms_. You could also say:

$ tar blues --create folk --file=collection.tar jazz

However, you can see that this order is harder to understand; this is
why we will list the arguments in the order that makes the commands
easiest to understand (and we encourage you to do the same when you use
`tar', to avoid errors).

Note that the part of the command which says,
`--file=collection.tar' is considered to be _one_ argument. If you
substituted any other string of characters for `collection.tar', then
that string would become the name of the archive file you create.

The order of the options becomes more important when you begin to use
short forms. With short forms, if you type commands in the wrong order
(even if you type them correctly in all other ways), you may end up with
results you don't expect. For this reason, it is a good idea to get
into the habit of typing options in the order that makes inherent sense.
*Note short create::, for more information on this.

In this example, you type the command as shown above: `--create' is
the operation which creates the new archive (`collection.tar'), and
`--file' is the option which lets you give it the name you chose. The
files, `blues', `folk', and `jazz', are now members of the archive,
`collection.tar' (they are "file name arguments" to the `--create'
operation). Now that they are in the archive, they are called _archive
members_, not files. (*note members: Definitions.).

When you create an archive, you _must_ specify which files you want
placed in the archive. If you do not specify any archive members, GNU
`tar' will complain.

If you now list the contents of the working directory (`ls'), you
will find the archive file listed as well as the files you saw
previously:

blues folk jazz collection.tar

Creating the archive `collection.tar' did not destroy the copies of the
files in the directory.

Keep in mind that if you don't indicate an operation, `tar' will not
run and will prompt you for one. If you don't name any files, `tar'
will complain. You must have write access to the working directory, or
else you will not be able to create an archive in that directory.

_Caution_: Do not attempt to use `--create' (`-c') to add files to
an existing archive; it will delete the archive and write a new one.
Use `--append' (`-r') instead. *Note append::.

File: tar.info, Node: create verbose, Next: short create, Prev: Creating the archive, Up: create

2.6.3 Running `--create' with `--verbose'
-----------------------------------------

If you include the `--verbose' (`-v') option on the command line, `tar'
will list the files it is acting on as it is working. In verbose mode,
the `create' example above would appear as:

$ tar --create --verbose --file=collection.tar blues folk jazz
blues
folk
jazz

This example is just like the example we showed which did not use
`--verbose', except that `tar' generated the remaining lines .

In the rest of the examples in this chapter, we will frequently use
`verbose' mode so we can show actions or `tar' responses that you would
otherwise not see, and which are important for you to understand.

File: tar.info, Node: short create, Next: create dir, Prev: create verbose, Up: create

2.6.4 Short Forms with `create'
-------------------------------

As we said before, the `--create' (`-c') operation is one of the most
basic uses of `tar', and you will use it countless times. Eventually,
you will probably want to use abbreviated (or "short") forms of
options. A full discussion of the three different forms that options
can take appears in *Note Styles::; for now, here is what the previous
example (including the `--verbose' (`-v') option) looks like using
short option forms:

$ tar -cvf collection.tar blues folk jazz
blues
folk
jazz

As you can see, the system responds the same no matter whether you use
long or short option forms.

One difference between using short and long option forms is that,
although the exact placement of arguments following options is no more
specific when using short forms, it is easier to become confused and
make a mistake when using short forms. For example, suppose you
attempted the above example in the following way:

$ tar -cfv collection.tar blues folk jazz

In this case, `tar' will make an archive file called `v', containing
the files `blues', `folk', and `jazz', because the `v' is the closest
"file name" to the `-f' option, and is thus taken to be the chosen
archive file name. `tar' will try to add a file called
`collection.tar' to the `v' archive file; if the file `collection.tar'
did not already exist, `tar' will report an error indicating that this
file does not exist. If the file `collection.tar' does already exist
(e.g., from a previous command you may have run), then `tar' will add
this file to the archive. Because the `-v' option did not get
registered, `tar' will not run under `verbose' mode, and will not
report its progress.

The end result is that you may be quite confused about what happened,
and possibly overwrite a file. To illustrate this further, we will show
you how an example we showed previously would look using short forms.

This example,

$ tar blues --create folk --file=collection.tar jazz

is confusing as it is. When shown using short forms, however, it
becomes much more so:

$ tar blues -c folk -f collection.tar jazz

It would be very easy to put the wrong string of characters immediately
following the `-f', but doing that could sacrifice valuable data.

For this reason, we recommend that you pay very careful attention to
the order of options and placement of file and archive names,
especially when using short option forms. Not having the option name
written out mnemonically can affect how well you remember which option
does what, and therefore where different names have to be placed.
(Placing options in an unusual order can also cause `tar' to report an
error if you have set the shell environment variable `POSIXLY_CORRECT'.)

File: tar.info, Node: create dir, Prev: short create, Up: create

2.6.5 Archiving Directories
---------------------------

You can archive a directory by specifying its directory name as a file
name argument to `tar'. The files in the directory will be archived
relative to the working directory, and the directory will be re-created
along with its contents when the archive is extracted.

To archive a directory, first move to its superior directory. If you
have followed the previous instructions in this tutorial, you should
type:

$ cd ..
$

This will put you into the directory which contains `practice', i.e.
your home directory. Once in the superior directory, you can specify
the subdirectory, `practice', as a file name argument. To store
`practice' in the new archive file `music.tar', type:

$ tar --create --verbose --file=music.tar practice

`tar' should output:

practice/
practice/blues
practice/folk
practice/jazz
practice/collection.tar

Note that the archive thus created is not in the subdirectory
`practice', but rather in the current working directory--the directory
from which `tar' was invoked. Before trying to archive a directory
from its superior directory, you should make sure you have write access
to the superior directory itself, not only the directory you are trying
archive with `tar'. For example, you will probably not be able to
store your home directory in an archive by invoking `tar' from the root
directory; *Note absolute::. (Note also that `collection.tar', the
original archive file, has itself been archived. `tar' will accept any
file as a file to be archived, regardless of its content. When
`music.tar' is extracted, the archive file `collection.tar' will be
re-written into the file system).

If you give `tar' a command such as

$ tar --create --file=foo.tar .

`tar' will report `tar: ./foo.tar is the archive; not dumped'. This
happens because `tar' creates the archive `foo.tar' in the current
directory before putting any files into it. Then, when `tar' attempts
to add all the files in the directory `.' to the archive, it notices
that the file `./foo.tar' is the same as the archive `foo.tar', and
skips it. (It makes no sense to put an archive into itself.) GNU `tar'
will continue in this case, and create the archive normally, except for
the exclusion of that one file. (_Please note:_ Other versions of
`tar' are not so clever; they will enter an infinite loop when this
happens, so you should not depend on this behavior unless you are
certain you are running GNU `tar'.)

File: tar.info, Node: list, Next: extract, Prev: create, Up: Tutorial

2.7 How to List Archives
========================

Frequently, you will find yourself wanting to determine exactly what a
particular archive contains. You can use the `--list' (`-t') operation
to get the member names as they currently appear in the archive, as well
as various attributes of the files at the time they were archived. For
example, you can examine the archive `collection.tar' that you created
in the last section with the command,

$ tar --list --file=collection.tar

The output of `tar' would then be:

blues
folk
jazz

The archive `bfiles.tar' would list as follows:

./birds
baboon
./box

Be sure to use a `--file=ARCHIVE-NAME' (`-f ARCHIVE-NAME') option just
as with `--create' (`-c') to specify the name of the archive.

If you use the `--verbose' (`-v') option with `--list', then `tar'
will print out a listing reminiscent of `ls -l', showing owner, file
size, and so forth.

If you had used `--verbose' (`-v') mode, the example above would look
like:

$ tar --list --verbose --file=collection.tar folk
-rw-rw-rw- myself user 62 1990-05-23 10:55 folk

You can specify one or more individual member names as arguments when
using `list'. In this case, `tar' will only list the names of members
you identify. For example, `tar --list --file=afiles.tar apple' would
only print `apple'.

Because `tar' preserves paths, file names must be specified as they
appear in the archive (ie., relative to the directory from which the
archive was created). Therefore, it is essential when specifying
member names to `tar' that you give the exact member names. For
example, `tar --list --file=bfiles birds' would produce an error message
something like `tar: birds: Not found in archive', because there is no
member named `birds', only one named `./birds'. While the names
`birds' and `./birds' name the same file, _member_ names are compared
using a simplistic name comparison, in which an exact match is
necessary. *Note absolute::.

However, `tar --list --file=collection.tar folk' would respond with
`folk', because `folk' is in the archive file `collection.tar'. If you
are not sure of the exact file name, try listing all the files in the
archive and searching for the one you expect to find; remember that if
you use `--list' with no file names as arguments, `tar' will print the
names of all the members stored in the specified archive.

* Menu:

* list dir::

File: tar.info, Node: list dir, Up: list

Listing the Contents of a Stored Directory
------------------------------------------

To get information about the contents of an archived directory, use the
directory name as a file name argument in conjunction with `--list'
(`-t'). To find out file attributes, include the `--verbose' (`-v')
option.

For example, to find out about files in the directory `practice', in
the archive file `music.tar', type:

$ tar --list --verbose --file=music.tar practice

`tar' responds:

drwxrwxrwx myself user 0 1990-05-31 21:49 practice/
-rw-rw-rw- myself user 42 1990-05-21 13:29 practice/blues
-rw-rw-rw- myself user 62 1990-05-23 10:55 practice/folk
-rw-rw-rw- myself user 40 1990-05-21 13:30 practice/jazz
-rw-rw-rw- myself user 10240 1990-05-31 21:49 practice/collection.tar

When you use a directory name as a file name argument, `tar' acts on
all the files (including sub-directories) in that directory.

File: tar.info, Node: extract, Next: going further, Prev: list, Up: Tutorial

2.8 How to Extract Members from an Archive
==========================================

_(This message will disappear, once this node revised.)_

Creating an archive is only half the job--there is no point in storing
files in an archive if you can't retrieve them. The act of retrieving
members from an archive so they can be used and manipulated as
unarchived files again is called "extraction". To extract files from
an archive, use the `--extract' (`--get', `-x') operation. As with
`--create' (`-c'), specify the name of the archive with
`--file=ARCHIVE-NAME' (`-f ARCHIVE-NAME'). Extracting an archive does
not modify the archive in any way; you can extract it multiple times if
you want or need to.

Using `--extract', you can extract an entire archive, or specific
files. The files can be directories containing other files, or not. As
with `--create' (`-c') and `--list' (`-t'), you may use the short or the
long form of the operation without affecting the performance.

* Menu:

* extracting archives::
* extracting files::
* extract dir::
* extracting untrusted archives::
* failing commands::

File: tar.info, Node: extracting archives, Next: extracting files, Up: extract

2.8.1 Extracting an Entire Archive
----------------------------------

To extract an entire archive, specify the archive file name only, with
no individual file names as arguments. For example,

$ tar -xvf collection.tar

produces this:

-rw-rw-rw- me user 28 1996-10-18 16:31 jazz
-rw-rw-rw- me user 21 1996-09-23 16:44 blues
-rw-rw-rw- me user 20 1996-09-23 16:44 folk

File: tar.info, Node: extracting files, Next: extract dir, Prev: extracting archives, Up: extract

2.8.2 Extracting Specific Files
-------------------------------

To extract specific archive members, give their exact member names as
arguments, as printed by `--list' (`-t'). If you had mistakenly deleted
one of the files you had placed in the archive `collection.tar' earlier
(say, `blues'), you can extract it from the archive without changing
the archive's structure. It will be identical to the original file
`blues' that you deleted. .

First, make sure you are in the `practice' directory, and list the
files in the directory. Now, delete the file, `blues', and list the
files in the directory again.

You can now extract the member `blues' from the archive file
`collection.tar' like this:

$ tar --extract --file=collection.tar blues

If you list the files in the directory again, you will see that the file
`blues' has been restored, with its original permissions, creation
times, and owner. (These parameters will be identical to those which
the file had when you originally placed it in the archive; any changes
you may have made before deleting the file from the file system,
however, will _not_ have been made to the archive member.) The archive
file, `collection.tar', is the same as it was before you extracted
`blues'. You can confirm this by running `tar' with `--list' (`-t').

Remember that as with other operations, specifying the exact member
name is important. `tar --extract --file=bfiles.tar birds' will fail,
because there is no member named `birds'. To extract the member named
`./birds', you must specify `tar --extract --file=bfiles.tar ./birds'.
To find the exact member names of the members of an archive, use
`--list' (`-t') (*note list::).

You can extract a file to standard output by combining the above
options with the `--to-stdout' (`-O') option (*note Writing to Standard
Output::).

If you give the `--verbose' (`-v') option, then `--extract'
(`--get', `-x') will print the names of the archive members as it
extracts them.

File: tar.info, Node: extract dir, Next: extracting untrusted archives, Prev: extracting files, Up: extract

2.8.3 Extracting Files that are Directories
-------------------------------------------

Extracting directories which are members of an archive is similar to
extracting other files. The main difference to be aware of is that if
the extracted directory has the same name as any directory already in
the working directory, then files in the extracted directory will be
placed into the directory of the same name. Likewise, if there are
files in the pre-existing directory with the same names as the members
which you extract, the files from the extracted archive will replace
the files already in the working directory (and possible
subdirectories). This will happen regardless of whether or not the
files in the working directory were more recent than those extracted
(there exist, however, special options that alter this behavior *note
Writing::).

However, if a file was stored with a directory name as part of its
file name, and that directory does not exist under the working
directory when the file is extracted, `tar' will create the directory.

We can demonstrate how to use `--extract' to extract a directory
file with an example. Change to the `practice' directory if you
weren't there, and remove the files `folk' and `jazz'. Then, go back
to the parent directory and extract the archive `music.tar'. You may
either extract the entire archive, or you may extract only the files
you just deleted. To extract the entire archive, don't give any file
names as arguments after the archive name `music.tar'. To extract only
the files you deleted, use the following command:

$ tar -xvf music.tar practice/folk practice/jazz
practice/folk
practice/jazz

If you were to specify two `--verbose' (`-v') options, `tar' would have
displayed more detail about the extracted files, as shown in the
example below:

$ tar -xvvf music.tar practice/folk practice/jazz
-rw-rw-rw- me user 28 1996-10-18 16:31 practice/jazz
-rw-rw-rw- me user 20 1996-09-23 16:44 practice/folk

Because you created the directory with `practice' as part of the file
names of each of the files by archiving the `practice' directory as
`practice', you must give `practice' as part of the file names when you
extract those files from the archive.

File: tar.info, Node: extracting untrusted archives, Next: failing commands, Prev: extract dir, Up: extract

2.8.4 Extracting Archives from Untrusted Sources
------------------------------------------------

Extracting files from archives can overwrite files that already exist.
If you receive an archive from an untrusted source, you should make a
new directory and extract into that directory, so that you don't have
to worry about the extraction overwriting one of your existing files.
For example, if `untrusted.tar' came from somewhere else on the
Internet, and you don't necessarily trust its contents, you can extract
it as follows:

$ mkdir newdir
$ cd newdir
$ tar -xvf ../untrusted.tar

It is also a good practice to examine contents of the archive before
extracting it, using `--list' (`-t') option, possibly combined with
`--verbose' (`-v').

File: tar.info, Node: failing commands, Prev: extracting untrusted archives, Up: extract

2.8.5 Commands That Will Fail
-----------------------------

Here are some sample commands you might try which will not work, and why
they won't work.

If you try to use this command,

$ tar -xvf music.tar folk jazz

you will get the following response:

tar: folk: Not found in archive
tar: jazz: Not found in archive
$

This is because these files were not originally _in_ the parent
directory `..', where the archive is located; they were in the
`practice' directory, and their file names reflect this:

$ tar -tvf music.tar
practice/folk
practice/jazz
practice/rock

Likewise, if you try to use this command,

$ tar -tvf music.tar folk jazz

you would get a similar response. Members with those names are not in
the archive. You must use the correct member names in order to extract
the files from the archive.

If you have forgotten the correct names of the files in the archive,
use `tar --list --verbose' to list them correctly.

File: tar.info, Node: going further, Prev: extract, Up: Tutorial

2.9 Going Further Ahead in this Manual
======================================

File: tar.info, Node: tar invocation, Next: operations, Prev: Tutorial, Up: Top

3 Invoking GNU `tar'
********************

_(This message will disappear, once this node revised.)_

This chapter is about how one invokes the GNU `tar' command, from the
command synopsis (*note Synopsis::). There are numerous options, and
many styles for writing them. One mandatory option specifies the
operation `tar' should perform (*note Operation Summary::), other
options are meant to detail how this operation should be performed
(*note Option Summary::). Non-option arguments are not always
interpreted the same way, depending on what the operation is.

You will find in this chapter everything about option styles and
rules for writing them (*note Styles::). On the other hand, operations
and options are fully described elsewhere, in other chapters. Here,
you will find only synthetic descriptions for operations and options,
together with pointers to other parts of the `tar' manual.

Some options are so special they are fully described right in this
chapter. They have the effect of inhibiting the normal operation of
`tar' or else, they globally alter the amount of feedback the user
receives about what is going on. These are the `--help' and
`--version' (*note help::), `--verbose' (`-v') (*note verbose::) and
`--interactive' (`-w') options (*note interactive::).

* Menu:

* Synopsis::
* using tar options::
* Styles::
* All Options::
* help::
* verbose::
* interactive::

File: tar.info, Node: Synopsis, Next: using tar options, Up: tar invocation

3.1 General Synopsis of `tar'
=============================

The GNU `tar' program is invoked as either one of:

tar OPTION... [NAME]...
tar LETTER... [ARGUMENT]... [OPTION]... [NAME]...

The second form is for when old options are being used.

You can use `tar' to store files in an archive, to extract them from
an archive, and to do other types of archive manipulation. The primary
argument to `tar', which is called the "operation", specifies which
action to take. The other arguments to `tar' are either "options",
which change the way `tar' performs an operation, or file names or
archive members, which specify the files or members `tar' is to act on.

You can actually type in arguments in any order, even if in this
manual the options always precede the other arguments, to make examples
easier to understand. Further, the option stating the main operation
mode (the `tar' main command) is usually given first.

Each NAME in the synopsis above is interpreted as an archive member
name when the main command is one of `--compare' (`--diff', `-d'),
`--delete', `--extract' (`--get', `-x'), `--list' (`-t') or `--update'
(`-u'). When naming archive members, you must give the exact name of
the member in the archive, as it is printed by `--list' (`-t'). For
`--append' (`-r') and `--create' (`-c'), these NAME arguments specify
the names of either files or directory hierarchies to place in the
archive. These files or hierarchies should already exist in the file
system, prior to the execution of the `tar' command.

`tar' interprets relative file names as being relative to the
working directory. `tar' will make all file names relative (by
removing leading slashes when archiving or restoring files), unless you
specify otherwise (using the `--absolute-names' (`-P') option).
*Note absolute::, for more information about `--absolute-names' (`-P').

If you give the name of a directory as either a file name or a member
name, then `tar' acts recursively on all the files and directories
beneath that directory. For example, the name `/' identifies all the
files in the filesystem to `tar'.

The distinction between file names and archive member names is
especially important when shell globbing is used, and sometimes a
source of confusion for newcomers. *Note Wildcards::, for more
information about globbing. The problem is that shells may only glob
using existing files in the file system. Only `tar' itself may glob on
archive members, so when needed, you must ensure that wildcard
characters reach `tar' without being interpreted by the shell first.
Using a backslash before `*' or `?', or putting the whole argument
between quotes, is usually sufficient for this.

Even if NAMEs are often specified on the command line, they can also
be read from a text file in the file system, using the
`--files-from=FILE-OF-NAMES' (`-T FILE-OF-NAMES') option.

If you don't use any file name arguments, `--append' (`-r'),
`--delete' and `--concatenate' (`--catenate', `-A') will do nothing,
while `--create' (`-c') will usually yield a diagnostic and inhibit
`tar' execution. The other operations of `tar' (`--list' (`-t'),
`--extract' (`--get', `-x'), `--compare' (`--diff', `-d'), and
`--update' (`-u')) will act on the entire contents of the archive.

Besides successful exits, GNU `tar' may fail for many reasons. Some
reasons correspond to bad usage, that is, when the `tar' command is
improperly written. Errors may be encountered later, while
encountering an error processing the archive or the files. Some errors
are recoverable, in which case the failure is delayed until `tar' has
completed all its work. Some errors are such that it would not
meaningful, or at least risky, to continue processing: `tar' then
aborts processing immediately. All abnormal exits, whether immediate
or delayed, should always be clearly diagnosed on `stderr', after a
line stating the nature of the error.

GNU `tar' returns only a few exit statuses. I'm really aiming
simplicity in that area, for now. If you are not using the `--compare'
(`--diff', `-d') option, zero means that everything went well, besides
maybe innocuous warnings. Nonzero means that something went wrong.
Right now, as of today, "nonzero" is almost always 2, except for remote
operations, where it may be 128.

File: tar.info, Node: using tar options, Next: Styles, Prev: Synopsis, Up: tar invocation

3.2 Using `tar' Options
=======================

GNU `tar' has a total of eight operating modes which allow you to
perform a variety of tasks. You are required to choose one operating
mode each time you employ the `tar' program by specifying one, and only
one operation as an argument to the `tar' command (two lists of four
operations each may be found at *Note frequent operations:: and *Note
Operations::). Depending on circumstances, you may also wish to
customize how the chosen operating mode behaves. For example, you may
wish to change the way the output looks, or the format of the files
that you wish to archive may require you to do something special in
order to make the archive look right.

You can customize and control `tar''s performance by running `tar'
with one or more options (such as `--verbose' (`-v'), which we used in
the tutorial). As we said in the tutorial, "options" are arguments to
`tar' which are (as their name suggests) optional. Depending on the
operating mode, you may specify one or more options. Different options
will have different effects, but in general they all change details of
the operation, such as archive format, archive name, or level of user
interaction. Some options make sense with all operating modes, while
others are meaningful only with particular modes. You will likely use
some options frequently, while you will only use others infrequently,
or not at all. (A full list of options is available in *note All
Options::.)

The `TAR_OPTIONS' environment variable specifies default options to
be placed in front of any explicit options. For example, if
`TAR_OPTIONS' is `-v --unlink-first', `tar' behaves as if the two
options `-v' and `--unlink-first' had been specified before any
explicit options. Option specifications are separated by whitespace.
A backslash escapes the next character, so it can be used to specify an
option containing whitespace or a backslash.

Note that `tar' options are case sensitive. For example, the
options `-T' and `-t' are different; the first requires an argument for
stating the name of a file providing a list of NAMEs, while the second
does not require an argument and is another way to write `--list'
(`-t').

In addition to the eight operations, there are many options to
`tar', and three different styles for writing both: long (mnemonic)
form, short form, and old style. These styles are discussed below.
Both the options and the operations can be written in any of these three
styles.

File: tar.info, Node: Styles, Next: All Options, Prev: using tar options, Up: tar invocation

3.3 The Three Option Styles
===========================

There are three styles for writing operations and options to the command
line invoking `tar'. The different styles were developed at different
times during the history of `tar'. These styles will be presented
below, from the most recent to the oldest.

Some options must take an argument. (For example,
`--file=ARCHIVE-NAME' (`-f ARCHIVE-NAME') takes the name of an archive
file as an argument. If you do not supply an archive file name, `tar'
will use a default, but this can be confusing; thus, we recommend that
you always supply a specific archive file name.) Where you _place_ the
arguments generally depends on which style of options you choose. We
will detail specific information relevant to each option style in the
sections on the different option styles, below. The differences are
subtle, yet can often be very important; incorrect option placement can
cause you to overwrite a number of important files. We urge you to
note these differences, and only use the option style(s) which makes
the most sense to you until you feel comfortable with the others.

Some options _may_ take an argument (currently, there are two such
options: `--backup' and `--occurrence'). Such options may have at most
long and short forms, they do not have old style equivalent. The rules
for specifying an argument for such options are stricter than those for
specifying mandatory arguments. Please, pay special attention to them.

* Menu:

* Mnemonic Options:: Mnemonic Option Style
* Short Options:: Short Option Style
* Old Options:: Old Option Style
* Mixing:: Mixing Option Styles

File: tar.info, Node: Mnemonic Options, Next: Short Options, Up: Styles

3.3.1 Mnemonic Option Style
---------------------------

Each option has at least one long (or mnemonic) name starting with two
dashes in a row, e.g. `--list'. The long names are more clear than
their corresponding short or old names. It sometimes happens that a
single mnemonic option has many different different names which are
synonymous, such as `--compare' and `--diff'. In addition, long option
names can be given unique abbreviations. For example, `--cre' can be
used in place of `--create' because there is no other mnemonic option
which begins with `cre'. (One way to find this out is by trying it and
seeing what happens; if a particular abbreviation could represent more
than one option, `tar' will tell you that that abbreviation is
ambiguous and you'll know that that abbreviation won't work. You may
also choose to run `tar --help' to see a list of options. Be aware
that if you run `tar' with a unique abbreviation for the long name of
an option you didn't want to use, you are stuck; `tar' will perform the
command as ordered.)

Mnemonic options are meant to be obvious and easy to remember, and
their meanings are generally easier to discern than those of their
corresponding short options (see below). For example:

$ tar --create --verbose --blocking-factor=20 --file=/dev/rmt0

gives a fairly good set of hints about what the command does, even for
those not fully acquainted with `tar'.

Mnemonic options which require arguments take those arguments
immediately following the option name. There are two ways of specifying
a mandatory argument. It can be separated from the option name either
by an equal sign, or by any amount of white space characters. For
example, the `--file' option (which tells the name of the `tar'
archive) is given a file such as `archive.tar' as argument by using any
of the following notations: `--file=archive.tar' or `--file
archive.tar'.

In contrast, optional arguments must always be introduced using an
equal sign. For example, the `--backup' option takes an optional
argument specifying backup type. It must be used as
`--backup=BACKUP-TYPE'.

File: tar.info, Node: Short Options, Next: Old Options, Prev: Mnemonic Options, Up: Styles

3.3.2 Short Option Style
------------------------

Most options also have a short option name. Short options start with a
single dash, and are followed by a single character, e.g. `-t' (which
is equivalent to `--list'). The forms are absolutely identical in
function; they are interchangeable.

The short option names are faster to type than long option names.

Short options which require arguments take their arguments
immediately following the option, usually separated by white space. It
is also possible to stick the argument right after the short option
name, using no intervening space. For example, you might write
`-f archive.tar' or `-farchive.tar' instead of using
`--file=archive.tar'. Both `--file=ARCHIVE-NAME' and `-f ARCHIVE-NAME'
denote the option which indicates a specific archive, here named
`archive.tar'.

Short options which take optional arguments take their arguments
immediately following the option letter, _without any intervening white
space characters_.

Short options' letters may be clumped together, but you are not
required to do this (as compared to old options; see below). When
short options are clumped as a set, use one (single) dash for them all,
e.g. ``tar' -cvf'. Only the last option in such a set is allowed to
have an argument(1).

When the options are separated, the argument for each option which
requires an argument directly follows that option, as is usual for Unix
programs. For example:

$ tar -c -v -b 20 -f /dev/rmt0

If you reorder short options' locations, be sure to move any
arguments that belong to them. If you do not move the arguments
properly, you may end up overwriting files.

---------- Footnotes ----------

(1) Clustering many options, the last of which has an argument, is a
rather opaque way to write options. Some wonder if GNU `getopt' should
not even be made helpful enough for considering such usages as invalid.

File: tar.info, Node: Old Options, Next: Mixing, Prev: Short Options, Up: Styles

3.3.3 Old Option Style
----------------------

_(This message will disappear, once this node revised.)_

Like short options, old options are single letters. However, old
options must be written together as a single clumped set, without
spaces separating them or dashes preceding them(1). This set of
letters must be the first to appear on the command line, after the
`tar' program name and some white space; old options cannot appear
anywhere else. The letter of an old option is exactly the same letter
as the corresponding short option. For example, the old option `t' is
the same as the short option `-t', and consequently, the same as the
mnemonic option `--list'. So for example, the command `tar cv'
specifies the option `-v' in addition to the operation `-c'.

When options that need arguments are given together with the command,
all the associated arguments follow, in the same order as the options.
Thus, the example given previously could also be written in the old
style as follows:

$ tar cvbf 20 /dev/rmt0

Here, `20' is the argument of `-b' and `/dev/rmt0' is the argument of
`-f'.

On the other hand, this old style syntax makes it difficult to match
option letters with their corresponding arguments, and is often
confusing. In the command `tar cvbf 20 /dev/rmt0', for example, `20'
is the argument for `-b', `/dev/rmt0' is the argument for `-f', and
`-v' does not have a corresponding argument. Even using short options
like in `tar -c -v -b 20 -f /dev/rmt0' is clearer, putting all
arguments next to the option they pertain to.

If you want to reorder the letters in the old option argument, be
sure to reorder any corresponding argument appropriately.

This old way of writing `tar' options can surprise even experienced
users. For example, the two commands:

tar cfz archive.tar.gz file
tar -cfz archive.tar.gz file

are quite different. The first example uses `archive.tar.gz' as the
value for option `f' and recognizes the option `z'. The second
example, however, uses `z' as the value for option `f' -- probably not
what was intended.

Old options are kept for compatibility with old versions of `tar'.

This second example could be corrected in many ways, among which the
following are equivalent:

tar -czf archive.tar.gz file
tar -cf archive.tar.gz -z file
tar cf archive.tar.gz -z file

As far as we know, all `tar' programs, GNU and non-GNU, support old
options. GNU `tar' supports them not only for historical reasons, but
also because many people are used to them. For compatibility with Unix
`tar', the first argument is always treated as containing command and
option letters even if it doesn't start with `-'. Thus, `tar c' is
equivalent to `tar -c': both of them specify the `--create' (`-c')
command to create an archive.

---------- Footnotes ----------

(1) Beware that if you precede options with a dash, you are
announcing the short option style instead of the old option style;
short options are decoded differently.

File: tar.info, Node: Mixing, Prev: Old Options, Up: Styles

3.3.4 Mixing Option Styles
--------------------------

All three styles may be intermixed in a single `tar' command, so long
as the rules for each style are fully respected(1). Old style options
and either of the modern styles of options may be mixed within a single
`tar' command. However, old style options must be introduced as the
first arguments only, following the rule for old options (old options
must appear directly after the `tar' command and some white space).
Modern options may be given only after all arguments to the old options
have been collected. If this rule is not respected, a modern option
might be falsely interpreted as the value of the argument to one of the
old style options.

For example, all the following commands are wholly equivalent, and
illustrate the many combinations and orderings of option styles.

tar --create --file=archive.tar
tar --create -f archive.tar
tar --create -farchive.tar
tar --file=archive.tar --create
tar --file=archive.tar -c
tar -c --file=archive.tar
tar -c -f archive.tar
tar -c -farchive.tar
tar -cf archive.tar
tar -cfarchive.tar
tar -f archive.tar --create
tar -f archive.tar -c
tar -farchive.tar --create
tar -farchive.tar -c
tar c --file=archive.tar
tar c -f archive.tar
tar c -farchive.tar
tar cf archive.tar
tar f archive.tar --create
tar f archive.tar -c
tar fc archive.tar

On the other hand, the following commands are _not_ equivalent to
the previous set:

tar -f -c archive.tar
tar -fc archive.tar
tar -fcarchive.tar
tar -farchive.tarc
tar cfarchive.tar

These last examples mean something completely different from what the
user intended (judging based on the example in the previous set which
uses long options, whose intent is therefore very clear). The first
four specify that the `tar' archive would be a file named `-c', `c',
`carchive.tar' or `archive.tarc', respectively. The first two examples
also specify a single non-option, NAME argument having the value
`archive.tar'. The last example contains only old style option letters
(repeating option `c' twice), not all of which are meaningful (eg., `.',
`h', or `i'), with no argument value.

---------- Footnotes ----------

(1) Before GNU `tar' version 1.11.6, a bug prevented intermixing old
style options with mnemonic options in some cases.

File: tar.info, Node: All Options, Next: help, Prev: Styles, Up: tar invocation

3.4 All `tar' Options
=====================

The coming manual sections contain an alphabetical listing of all `tar'
operations and options, with brief descriptions and cross references to
more in-depth explanations in the body of the manual. They also
contain an alphabetically arranged table of the short option forms with
their corresponding long option. You can use this table as a reference
for deciphering `tar' commands in scripts.

* Menu:

* Operation Summary::
* Option Summary::
* Short Option Summary::

File: tar.info, Node: Operation Summary, Next: Option Summary, Up: All Options

3.4.1 Operations
----------------

`--append'
`-r'
Appends files to the end of the archive. *Note append::.

`--catenate'
`-A'
Same as `--concatenate'. *Note concatenate::.

`--compare'
`-d'
Compares archive members with their counterparts in the file
system, and reports differences in file size, mode, owner,
modification date and contents. *Note compare::.

`--concatenate'
`-A'
Appends other `tar' archives to the end of the archive. *Note
concatenate::.

`--create'
`-c'
Creates a new `tar' archive. *Note create::.

`--delete'
Deletes members from the archive. Don't try this on a archive on a
tape! *Note delete::.

`--diff'
`-d'
Same `--compare'. *Note compare::.

`--extract'
`-x'
Extracts members from the archive into the file system. *Note
extract::.

`--get'
`-x'
Same as `--extract'. *Note extract::.

`--list'
`-t'
Lists the members in an archive. *Note list::.

`--update'
`-u'
Adds files to the end of the archive, but only if they are newer
than their counterparts already in the archive, or if they do not
already exist in the archive. *Note update::.

File: tar.info, Node: Option Summary, Next: Short Option Summary, Prev: Operation Summary, Up: All Options

3.4.2 `tar' Options
-------------------

`--absolute-names'
`-P'
Normally when creating an archive, `tar' strips an initial `/'
from member names. This option disables that behavior.

`--after-date'
(See `--newer'.)

`--anchored'
An exclude pattern must match an initial subsequence of the name's
components.

`--atime-preserve'
Tells `tar' to preserve the access time field in a file's inode
when reading it. Due to limitations in the `utimes' system call,
the modification time field is also preserved, which may cause
problems if the file is simultaneously being modified by another
program. This option is incompatible with incremental backups,
because preserving the access time involves updating the
last-changed time. Also, this option does not work on files that
you do not own, unless you're root.

`--backup=BACKUP-TYPE'
Rather than deleting files from the file system, `tar' will back
them up using simple or numbered backups, depending upon
BACKUP-TYPE.

`--block-number'
`-R'
With this option present, `tar' prints error messages for read
errors with the block number in the archive file.

`--blocking-factor=BLOCKING'
`-b BLOCKING'
Sets the blocking factor `tar' uses to BLOCKING x 512 bytes per
record.

`--bzip2'
`-j'
This option tells `tar' to read or write archives through `bzip2'.

`--checkpoint'
This option directs `tar' to print periodic checkpoint messages as
it reads through the archive. Its intended for when you want a
visual indication that `tar' is still running, but don't want to
see `--verbose' output.

`--check-links'
`-l'
If this option was given, `tar' will check the number of links
dumped for each processed file. If this number does not match the
total number of hard links for the file, a warning message will be
output.

Future versions will take `-l' as a short version of
`--check-links'. However, current release still retains the old
semantics for `-l'.

*Note Current status::, for more information.

`--compress'
`--uncompress'
`-Z'
`tar' will use the `compress' program when reading or writing the
archive. This allows you to directly act on archives while saving
space.

`--confirmation'
(See `--interactive'.)

`--dereference'
`-h'
When creating a `tar' archive, `tar' will archive the file that a
symbolic link points to, rather than archiving the symlink.

`--directory=DIR'
`-C DIR'
When this option is specified, `tar' will change its current
directory to DIR before performing any operations. When this
option is used during archive creation, it is order sensitive.

`--exclude=PATTERN'
When performing operations, `tar' will skip files that match
PATTERN.

`--exclude-from=FILE'
`-X FILE'
Similar to `--exclude', except `tar' will use the list of patterns
in the file FILE.

`--exclude-caches'
Automatically excludes all directories containing a cache
directory tag.

`--file=ARCHIVE'
`-f ARCHIVE'
`tar' will use the file ARCHIVE as the `tar' archive it performs
operations on, rather than `tar''s compilation dependent default.

`--files-from=FILE'
`-T FILE'
`tar' will use the contents of FILE as a list of archive members
or files to operate on, in addition to those specified on the
command-line.

`--force-local'
Forces `tar' to interpret the filename given to `--file' as a
local file, even if it looks like a remote tape drive name.

`--format=FORMAT'
Selects output archive format. FORMAT may be one of the following:

`v7'
Creates an archive that is compatible with Unix V7 `tar'.

`oldgnu'
Creates an archive that is compatible with GNU `tar' version
1.12 or earlier.

`gnu'
Creates archive in GNU tar 1.13 format. Basically it is the
same as `oldgnu' with the only difference in the way it
handles long numeric fields.

`ustar'
Creates a POSIX.1-1988 compatible archive.

`posix'
Creates a POSIX.1-2001 archive.

*Note Formats::, for a detailed discussion of these formats.

`--group=GROUP'
Files added to the `tar' archive will have a group id of GROUP,
rather than the group from the source file. GROUP is first decoded
as a group symbolic name, but if this interpretation fails, it has
to be a decimal numeric group ID.

Also see the comments for the `--owner=USER' option.

`--gzip'
`--gunzip'
`--ungzip'
`-z'
This option tells `tar' to read or write archives through `gzip',
allowing `tar' to directly operate on several kinds of compressed
archives transparently.

`--help'
`tar' will print out a short message summarizing the operations and
options to `tar' and exit.

`--ignore-case'
Ignore case when excluding files.

`--ignore-failed-read'
Do not exit unsuccessfully merely because an unreadable file was
encountered. *Note Reading::.

`--ignore-zeros'
`-i'
With this option, `tar' will ignore zeroed blocks in the archive,
which normally signals EOF. *Note Reading::.

`--incremental'
`-G'
Used to inform `tar' that it is working with an old GNU-format
incremental backup archive. It is intended primarily for
backwards compatibility only.

`--index-file=FILE'
Send verbose output to FILE instead of to standard output.

`--info-script=SCRIPT-FILE'
`--new-volume-script=SCRIPT-FILE'
`-F SCRIPT-FILE'
When `tar' is performing multi-tape backups, SCRIPT-FILE is run at
the end of each tape. If SCRIPT-FILE exits with nonzero status,
`tar' fails immediately.

`--interactive'
`--confirmation'
`-w'
Specifies that `tar' should ask the user for confirmation before
performing potentially destructive options, such as overwriting
files.

`--keep-newer-files'
Do not replace existing files that are newer than their archive
copies when extracting files from an archive.

`--keep-old-files'
`-k'
Do not overwrite existing files when extracting files from an
archive. *Note Writing::.

`--label=NAME'
`-V NAME'
When creating an archive, instructs `tar' to write NAME as a name
record in the archive. When extracting or listing archives, `tar'
will only operate on archives that have a label matching the
pattern specified in NAME.

`--listed-incremental=SNAPSHOT-FILE'
`-g SNAPSHOT-FILE'
During a `--create' operation, specifies that the archive that
`tar' creates is a new GNU-format incremental backup, using
SNAPSHOT-FILE to determine which files to backup. With other
operations, informs `tar' that the archive is in incremental
format.

`--mode=PERMISSIONS'
When adding files to an archive, `tar' will use PERMISSIONS for
the archive members, rather than the permissions from the files.
The program `chmod' and this `tar' option share the same syntax
for what PERMISSIONS might be. *Note Permissions: (fileutils)File
permissions. This reference also has useful information for those
not being overly familiar with the Unix permission system.

Of course, PERMISSIONS might be plainly specified as an octal
number. However, by using generic symbolic modifications to mode
bits, this allows more flexibility. For example, the value `a+rw'
adds read and write permissions for everybody, while retaining
executable bits on directories or on any other file already marked
as executable.

`--multi-volume'
`-M'
Informs `tar' that it should create or otherwise operate on a
multi-volume `tar' archive.

`--new-volume-script'
(see -info-script)

`-n'
`--seek'
Assume that the archive media supports seeks to arbitrary
locations. Usually `tar' determines automatically whether the
archive can be seeked or not. This option is intended for use in
cases when such recognition fails.

`--newer=DATE'
`--after-date=DATE'
`-N'
When creating an archive, `tar' will only add files that have
changed since DATE. If DATE begins with `/' or `.', it is taken
to be the name of a file whose last-modified time specifies the
date.

`--newer-mtime=DATE'
Like `--newer', but add only files whose contents have changed (as
opposed to just `--newer', which will also back up files for which
any status information has changed).

`--no-anchored'
An exclude pattern can match any subsequence of the name's
components.

`--no-ignore-case'
Use case-sensitive matching when excluding files.

`--no-recursion'
With this option, `tar' will not recurse into directories.

`--no-same-owner'
`-o'
When extracting an archive, do not attempt to preserve the owner
specified in the `tar' archive. This the default behavior for
ordinary users; this option has an effect only for the superuser.

`--no-same-permissions'
When extracting an archive, subtract the user's umask from files
from the permissions specified in the archive. This is the
default behavior for ordinary users; this option has an effect
only for the superuser.

`--no-wildcards'
Do not use wildcards when excluding files.

`--no-wildcards-match-slash'
Wildcards do not match `/' when excluding files.

`--null'
When `tar' is using the `--files-from' option, this option
instructs `tar' to expect filenames terminated with `NUL', so
`tar' can correctly work with file names that contain newlines.

`--numeric-owner'
This option will notify `tar' that it should use numeric user and
group IDs when creating a `tar' file, rather than names.

`-o'
When extracting files, this option is a synonym for
`--no-same-owner', i.e. it prevents `tar' from restoring ownership
of files being extracted.

When creating an archive, `-o' is a synonym for `--old-archive'.
This behavior is for compatibility with previous versions of GNU
`tar', and will be removed in the future releases.

*Note Current status::, for more information.

`--occurrence[=NUMBER]'
This option can be used in conjunction with one of the subcommands
`--delete', `--diff', `--extract' or `--list' when a list of files
is given either on the command line or via `-T' option.

This option instructs `tar' to process only the NUMBERth
occurrence of each named file. NUMBER defaults to 1, so

tar -x -f archive.tar --occurrence filename

will extract the first occurrence of `filename' from `archive.tar'
and will terminate without scanning to the end of the archive.

`--old-archive'
Synonym for `--format=v7'.

`--one-file-system'
`-l'
Used when creating an archive. Prevents `tar' from recursing into
directories that are on different file systems from the current
directory.

Earlier versions of GNU `tar' understood `-l' as a synonym for
`--one-file-system'. Although such usage is still allowed in the
present version, it is _strongly discouraged_. The future
versions of GNU `tar' will use `-l' as a synonym for
`--check-links'.

*Note Current status::, for more information.

`--overwrite'
Overwrite existing files and directory metadata when extracting
files from an archive. *Note Overwrite Old Files::.

`--overwrite-dir'
Overwrite the metadata of existing directories when extracting
files from an archive. *Note Overwrite Old Files::.

`--owner=USER'
Specifies that `tar' should use USER as the owner of members when
creating archives, instead of the user associated with the source
file. USER is first decoded as a user symbolic name, but if this
interpretation fails, it has to be a decimal numeric user ID.

There is no value indicating a missing number, and `0' usually
means `root'. Some people like to force `0' as the value to offer
in their distributions for the owner of files, because the `root'
user is anonymous anyway, so that might as well be the owner of
anonymous archives.

This option does not affect extraction from archives.

`--pax-option=KEYWORD-LIST'
This option is meaningful only with POSIX.1-2001 archives (). It
modifies the way `tar' handles the extended header keywords.
KEYWORD-LIST is a comma-separated list of keyword options, each
keyword option taking one of the following forms:

delete=PATTERN
When used with one of archive-creation command (), this
option instructs `tar' to omit from extended header records
that it produces any keywords matching the string PATTERN.

When used in extract or list mode, this option instructs tar
to ignore any keywords matching the given PATTERN in the
extended header records. In both cases, matching is performed
using the pattern matching notation described in POSIX
1003.2, 3.13 . For example:

--pax-option delete=security.*

would suppress security-related information.

exthdr.name=STRING
This keyword allows user control over the name that is
written into the ustar header blocks for the extended
headers. The name is obtained from STRING after substituting
the following meta-characters:

Meta-character Replaced By
%d The directory name of the file, equivalent
to the result of the `dirname' utility on
the translated pathname.
%f The filename of the file, equivalent to
the result of the `basename' utility on
the translated pathname.
%p The process ID of the `tar' process.
%% A `%' character.

Any other `%' characters in STRING produce undefined results.

If no option `exthdr.name=string' is specified, `tar' will
use the following default value:

%d/PaxHeaders.%p/%f

globexthdr.name=STRING
This keyword allows user control over the name that is
written into the ustar header blocks for global extended
header records. The name shall will be obtained from the
contents of STRING, after the following character
substitutions have been made:

Meta-character Replaced By
%n An integer that represents the sequence
number of the global extended header
record in the archive, starting at 1.
%p The process ID of the `tar' process.
%% A `%' character.

Any other `%' characters in string produce undefined results.

If no option `globexthdr.name=string' is specified, `tar'
will use the following default value:

$TMPDIR/GlobalHead.%p.%n

where `$TMPDIR' represents the value of the TMPDIR
environment variable. If TMPDIR is not set, `tar' uses `/tmp'.

KEYWORD=VALUE
When used with one of archive-creation commands, these
keyword/value pairs will be included at the beginning of the
archive in a global extended header record. When used with
one of archive-reading commands, `tar' will behave as if it
has encountered these keyword/value pairs at the beginning of
the archive in a global extended header record.

KEYWORD:=VALUE
When used with one of archive-creation commands, these
keyword/value pairs will be included as records at the
beginning of an extended header for each file. This is
effectively equivalent to KEYWORD=VALUE form except that it
creates no global extended header records.

When used with one of archive-reading commands, `tar' will
behave as if these keyword/value pairs were included as
records at the end of each extended header; thus, they will
override any global or file-specific extended header record
keywords of the same names. For example, in the command:

tar --format=posix --create \
--file archive --pax-option gname:=user .

the group name will be forced to a new value for all files
stored in the archive.

`--portability'
`--old-archive'
Synonym for `--format=v7'.

`--posix'
Same as `--format=posix'.

`--preserve'
Synonymous with specifying both `--preserve-permissions' and
`--same-order'.

`--preserve-order'
(See `--same-order'; *note Reading::.)

`--preserve-permissions'
`--same-permissions'
`-p'
When `tar' is extracting an archive, it normally subtracts the
users' umask from the permissions specified in the archive and uses
that number as the permissions to create the destination file.
Specifying this option instructs `tar' that it should use the
permissions directly from the archive. *Note Writing::.

`--read-full-records'
`-B'
Specifies that `tar' should reblock its input, for reading from
pipes on systems with buggy implementations. *Note Reading::.

`--record-size=SIZE'
Instructs `tar' to use SIZE bytes per record when accessing the
archive.

`--recursion'
With this option, `tar' recurses into directories.

`--recursive-unlink'
Remove existing directory hierarchies before extracting
directories of the same name from the archive. *Note Writing::.

`--remove-files'
Directs `tar' to remove the source file from the file system after
appending it to an archive.

`--rmt-command=CMD'
Notifies `tar' that it should use CMD instead of the default
`/usr/libexec/rmt' (*note Remote Tape Server::).

`--rsh-command=CMD'
Notifies `tar' that is should use CMD to communicate with remote
devices.

`--same-order'
`--preserve-order'
`-s'
This option is an optimization for `tar' when running on machines
with small amounts of memory. It informs `tar' that the list of
file arguments has already been sorted to match the order of files
in the archive. *Note Reading::.

`--same-owner'
When extracting an archive, `tar' will attempt to preserve the
owner specified in the `tar' archive with this option present.
This is the default behavior for the superuser; this option has an
effect only for ordinary users.

`--same-permissions'
(See `--preserve-permissions'; *note Writing::.)

`--show-defaults'
Displays the default options used by `tar' and exits successfully.
This option is intended for use in shell scripts. Here is an
example of what you can see using this option:

$ tar --show-defaults
--format=gnu -f- -b20

`--show-omitted-dirs'
Instructs `tar' to mention directories its skipping over when
operating on a `tar' archive.

`--sparse'
`-S'
Invokes a GNU extension when adding files to an archive that
handles sparse files efficiently.

`--starting-file=NAME'
`-K NAME'
This option affects extraction only; `tar' will skip extracting
files in the archive until it finds one that matches NAME. *Note
Scarce::.

`--strip-components=NUMBER'
Strip given NUMBER of leading components from file names before
extraction.(1) For example, if archive `archive.tar' contained
`/some/file/name', then running

tar --extract --file archive.tar --strip-components=2

would extracted this file to file `name'.

`--suffix=SUFFIX'
Alters the suffix `tar' uses when backing up files from the default
`~'.

`--tape-length=NUM'
`-L NUM'
Specifies the length of tapes that `tar' is writing as being
NUM x 1024 bytes long.

`--to-stdout'
`-O'
During extraction, `tar' will extract files to stdout rather than
to the file system. *Note Writing::.

`--totals'
Displays the total number of bytes written after creating an
archive.

`--touch'
`-m'
Sets the modification time of extracted files to the extraction
time, rather than the modification time stored in the archive.
*Note Writing::.

`--uncompress'
(See `--compress'.)

`--ungzip'
(See `--gzip'.)

`--unlink-first'
`-U'
Directs `tar' to remove the corresponding file from the file
system before extracting it from the archive. *Note Writing::.

`--use-compress-program=PROG'
Instructs `tar' to access the archive through PROG, which is
presumed to be a compression program of some sort.

`--utc'
Display file modification dates in UTC. This option implies
`--verbose'.

`--verbose'
`-v'
Specifies that `tar' should be more verbose about the operations
its performing. This option can be specified multiple times for
some operations to increase the amount of information displayed.

`--verify'
`-W'
Verifies that the archive was correctly written when creating an
archive.

`--version'
`tar' will print an informational message about what version it is
and a copyright message, some credits, and then exit.

`--volno-file=FILE'
Used in conjunction with `--multi-volume'. `tar' will keep track
of which volume of a multi-volume archive its working in FILE.

`--wildcards'
Use wildcards when excluding files.

`--wildcards-match-slash'
Wildcards match `/' when excluding files.

---------- Footnotes ----------

(1) This option was called `--strip-path' in version 1.14.

File: tar.info, Node: Short Option Summary, Prev: Option Summary, Up: All Options

3.4.3 Short Options Cross Reference
-----------------------------------

Here is an alphabetized list of all of the short option forms, matching
them with the equivalent long option.

`-A'
`--concatenate'

`-B'
`--read-full-records'

`-C'
`--directory'

`-F'
`--info-script'

`-G'
`--incremental'

`-K'
`--starting-file'

`-L'
`--tape-length'

`-M'
`--multi-volume'

`-N'
`--newer'

`-O'
`--to-stdout'

`-P'
`--absolute-names'

`-R'
`--block-number'

`-S'
`--sparse'

`-T'
`--files-from'

`-U'
`--unlink-first'

`-V'
`--label'

`-W'
`--verify'

`-X'
`--exclude-from'

`-Z'
`--compress'

`-b'
`--blocking-factor'

`-c'
`--create'

`-d'
`--compare'

`-f'
`--file'

`-g'
`--listed-incremental'

`-h'
`--dereference'

`-i'
`--ignore-zeros'

`-j'
`--bzip2'

`-k'
`--keep-old-files'

`-l'
`--one-file-system'. Use of this short option is deprecated. It is
retained for compatibility with the earlier versions of GNU `tar',
and will be changed in future releases.

*Note Current status::, for more information.

`-m'
`--touch'

`-o'
When creating -- `--no-same-owner', when extracting --
`--portability'.

The later usage is deprecated. It is retained for compatibility
with the earlier versions of GNU `tar'. In the future releases
`-o' will be equivalent to `--no-same-owner' only.

`-p'
`--preserve-permissions'

`-r'
`--append'

`-s'
`--same-order'

`-t'
`--list'

`-u'
`--update'

`-v'
`--verbose'

`-w'
`--interactive'

`-x'
`--extract'

`-z'
`--gzip'

File: tar.info, Node: help, Next: verbose, Prev: All Options, Up: tar invocation

3.5 GNU `tar' documentation
===========================

Being careful, the first thing is really checking that you are using
GNU `tar', indeed. The `--version' option will generate a message
giving confirmation that you are using GNU `tar', with the precise
version of GNU `tar' you are using. `tar' identifies itself and prints
the version number to the standard output, then immediately exits
successfully, without doing anything else, ignoring all other options.
For example, `tar --version' might return:

tar (GNU tar) 1.15.1

The first occurrence of `tar' in the result above is the program name
in the package (for example, `rmt' is another program), while the
second occurrence of `tar' is the name of the package itself,
containing possibly many programs. The package is currently named
`tar', after the name of the main program it contains(1).

Another thing you might want to do is checking the spelling or
meaning of some particular `tar' option, without resorting to this
manual, for once you have carefully read it. GNU `tar' has a short
help feature, triggerable through the `--help' option. By using this
option, `tar' will print a usage message listing all available options
on standard output, then exit successfully, without doing anything else
and ignoring all other options. Even if this is only a brief summary,
it may be several screens long. So, if you are not using some kind of
scrollable window, you might prefer to use something like:

$ tar --help | less

presuming, here, that you like using `less' for a pager. Other popular
pagers are `more' and `pg'. If you know about some KEYWORD which
interests you and do not want to read all the `--help' output, another
common idiom is doing:

tar --help | grep KEYWORD

for getting only the pertinent lines.

The perceptive reader would have noticed some contradiction in the
previous paragraphs. It is written that both `--version' and `--help'
print something, and have all other options ignored. In fact, they
cannot ignore each other, and one of them has to win. We do not
specify which is stronger, here; experiment if you really wonder!

The short help output is quite succinct, and you might have to get
back to the full documentation for precise points. If you are reading
this paragraph, you already have the `tar' manual in some form. This
manual is available in printed form, as a kind of small book. It may
printed out of the GNU `tar' distribution, provided you have TeX
already installed somewhere, and a laser printer around. Just
configure the distribution, execute the command `make dvi', then print
`doc/tar.dvi' the usual way (contact your local guru to know how). If
GNU `tar' has been conveniently installed at your place, this manual is
also available in interactive, hypertextual form as an Info file. Just
call `info tar' or, if you do not have the `info' program handy, use
the Info reader provided within GNU Emacs, calling `tar' from the main
Info menu.

There is currently no `man' page for GNU `tar'. If you observe such
a `man' page on the system you are running, either it does not long to
GNU `tar', or it has not been produced by GNU. Currently, GNU `tar'
documentation is provided in Texinfo format only, if we except, of
course, the short result of `tar --help'.

---------- Footnotes ----------

(1) There are plans to merge the `cpio' and `tar' packages into a
single one which would be called `paxutils'. So, who knows if, one of
this days, the `--version' would not yield `tar (GNU paxutils) 3.2'

File: tar.info, Node: verbose, Next: interactive, Prev: help, Up: tar invocation

3.6 Checking `tar' progress
===========================

Typically, `tar' performs most operations without reporting any
information to the user except error messages. When using `tar' with
many options, particularly ones with complicated or
difficult-to-predict behavior, it is possible to make serious mistakes.
`tar' provides several options that make observing `tar' easier. These
options cause `tar' to print information as it progresses in its job,
and you might want to use them just for being more careful about what
is going on, or merely for entertaining yourself. If you have
encountered a problem when operating on an archive, however, you may
need more information than just an error message in order to solve the
problem. The following options can be helpful diagnostic tools.

Normally, the `--list' (`-t') command to list an archive prints just
the file names (one per line) and the other commands are silent. When
used with most operations, the `--verbose' (`-v') option causes `tar'
to print the name of each file or archive member as it is processed.
This and the other options which make `tar' print status information
can be useful in monitoring `tar'.

With `--create' (`-c') or `--extract' (`--get', `-x'), `--verbose'
(`-v') used once just prints the names of the files or members as they
are processed. Using it twice causes `tar' to print a longer listing
(reminiscent of `ls -l') for each member. Since `--list' (`-t')
already prints the names of the members, `--verbose' (`-v') used once
with `--list' (`-t') causes `tar' to print an `ls -l' type listing of
the files in the archive. The following examples both extract members
with long list output:

$ tar --extract --file=archive.tar --verbose --verbose
$ tar xvvf archive.tar

Verbose output appears on the standard output except when an archive
is being written to the standard output, as with `tar --create --file=-
--verbose' (`tar cfv -', or even `tar cv'--if the installer let
standard output be the default archive). In that case `tar' writes
verbose output to the standard error stream.

If `--index-file=FILE' is specified, `tar' sends verbose output to
FILE rather than to standard output or standard error.

The `--totals' option--which is only meaningful when used with
`--create' (`-c')--causes `tar' to print the total amount written to
the archive, after it has been fully created.

The `--checkpoint' option prints an occasional message as `tar'
reads or writes the archive. In fact, it prints a message each 10
records read or written. It is designed for those who don't need the
more detailed (and voluminous) output of `--block-number' (`-R'), but
do want visual confirmation that `tar' is actually making forward
progress.

The `--show-omitted-dirs' option, when reading an archive--with
`--list' (`-t') or `--extract' (`--get', `-x'), for example--causes a
message to be printed for each directory in the archive which is
skipped. This happens regardless of the reason for skipping: the
directory might not have been named on the command line (implicitly or
explicitly), it might be excluded by the use of the `--exclude=PATTERN'
option, or some other reason.

If `--block-number' (`-R') is used, `tar' prints, along with every
message it would normally produce, the block number within the archive
where the message was triggered. Also, supplementary messages are
triggered when reading blocks full of NULs, or when hitting end of file
on the archive. As of now, if the archive if properly terminated with
a NUL block, the reading of the file may stop before end of file is
met, so the position of end of file will not usually show when
`--block-number' (`-R') is used. Note that GNU `tar' drains the
archive before exiting when reading the archive from a pipe.

This option is especially useful when reading damaged archives, since
it helps pinpoint the damaged sections. It can also be used with
`--list' (`-t') when listing a file-system backup tape, allowing you to
choose among several backup tapes when retrieving a file later, in
favor of the tape where the file appears earliest (closest to the front
of the tape).

File: tar.info, Node: interactive, Prev: verbose, Up: tar invocation

3.7 Asking for Confirmation During Operations
=============================================

Typically, `tar' carries out a command without stopping for further
instructions. In some situations however, you may want to exclude some
files and archive members from the operation (for instance if disk or
storage space is tight). You can do this by excluding certain files
automatically (*note Choosing::), or by performing an operation
interactively, using the `--interactive' (`-w') option. `tar' also
accepts `--confirmation' for this option.

When the `--interactive' (`-w') option is specified, before reading,
writing, or deleting files, `tar' first prints a message for each such
file, telling what operation it intends to take, then asks for
confirmation on the terminal. The actions which require confirmation
include adding a file to the archive, extracting a file from the
archive, deleting a file from the archive, and deleting a file from
disk. To confirm the action, you must type a line of input beginning
with `y'. If your input line begins with anything other than `y',
`tar' skips that file.

If `tar' is reading the archive from the standard input, `tar' opens
the file `/dev/tty' to support the interactive communications.

Verbose output is normally sent to standard output, separate from
other error messages. However, if the archive is produced directly on
standard output, then verbose output is mixed with errors on `stderr'.
Producing the archive on standard output may be used as a way to avoid
using disk space, when the archive is soon to be consumed by another
process reading it, say. Some people felt the need of producing an
archive on stdout, still willing to segregate between verbose output
and error output. A possible approach would be using a named pipe to
receive the archive, and having the consumer process to read from that
named pipe. This has the advantage of letting standard output free to
receive verbose output, all separate from errors.

File: tar.info, Node: operations, Next: Backups, Prev: tar invocation, Up: Top

4 GNU `tar' Operations
**********************

* Menu:

* Basic tar::
* Advanced tar::
* create options::
* extract options::
* backup::
* Applications::
* looking ahead::

File: tar.info, Node: Basic tar, Next: Advanced tar, Up: operations

4.1 Basic GNU `tar' Operations
==============================

The basic `tar' operations, `--create' (`-c'), `--list' (`-t') and
`--extract' (`--get', `-x'), are currently presented and described in
the tutorial chapter of this manual. This section provides some
complementary notes for these operations.

`--create' (`-c')
Creating an empty archive would have some kind of elegance. One
can initialize an empty archive and later use `--append' (`-r')
for adding all members. Some applications would not welcome
making an exception in the way of adding the first archive member.
On the other hand, many people reported that it is dangerously
too easy for `tar' to destroy a magnetic tape with an empty
archive(1). The two most common errors are:

1. Mistakingly using `create' instead of `extract', when the
intent was to extract the full contents of an archive. This
error is likely: keys `c' and `x' are right next to each
other on the QWERTY keyboard. Instead of being unpacked, the
archive then gets wholly destroyed. When users speak about
"exploding" an archive, they usually mean something else :-).

2. Forgetting the argument to `file', when the intent was to
create an archive with a single file in it. This error is
likely because a tired user can easily add the `f' key to the
cluster of option letters, by the mere force of habit,
without realizing the full consequence of doing so. The
usual consequence is that the single file, which was meant to
be saved, is rather destroyed.

So, recognizing the likelihood and the catastrophical nature of
these errors, GNU `tar' now takes some distance from elegance, and
cowardly refuses to create an archive when `--create' (`-c')
option is given, there are no arguments besides options, and
`--files-from=FILE-OF-NAMES' (`-T FILE-OF-NAMES') option is _not_
used. To get around the cautiousness of GNU `tar' and
nevertheless create an archive with nothing in it, one may still
use, as the value for the `--files-from=FILE-OF-NAMES' (`-T
FILE-OF-NAMES') option, a file with no names in it, as shown in
the following commands:

tar --create --file=empty-archive.tar --files-from=/dev/null
tar cfT empty-archive.tar /dev/null

`--extract' (`--get', `-x')
A socket is stored, within a GNU `tar' archive, as a pipe.

`--list' (`-t')
GNU `tar' now shows dates as `1996-08-30', while it used to show
them as `Aug 30 1996'. (One can revert to the old behavior by
defining `USE_OLD_CTIME' in `src/list.c' before reinstalling.)
But preferably, people should get used to ISO 8601 dates. Local
American dates should be made available again with full date
localization support, once ready. In the meantime, programs not
being localizable for dates should prefer international dates,
that's really the way to go.

Look up `http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html' if
you are curious, it contains a detailed explanation of the ISO
8601 standard.

---------- Footnotes ----------

(1) This is well described in `Unix-haters Handbook', by Simson
Garfinkel, Daniel Weise & Steven Strassmann, IDG Books, ISBN
1-56884-203-1.

File: tar.info, Node: Advanced tar, Next: create options, Prev: Basic tar, Up: operations

4.2 Advanced GNU `tar' Operations
=================================

Now that you have learned the basics of using GNU `tar', you may want
to learn about further ways in which `tar' can help you.

This chapter presents five, more advanced operations which you
probably won't use on a daily basis, but which serve more specialized
functions. We also explain the different styles of options and why you
might want to use one or another, or a combination of them in your `tar'
commands. Additionally, this chapter includes options which allow you
to define the output from `tar' more carefully, and provide help and
error correction in special circumstances.

* Menu:

* Operations::
* append::
* update::
* concatenate::
* delete::
* compare::

File: tar.info, Node: Operations, Next: append, Up: Advanced tar

4.2.1 The Five Advanced `tar' Operations
----------------------------------------

_(This message will disappear, once this node revised.)_

In the last chapter, you learned about the first three operations to
`tar'. This chapter presents the remaining five operations to `tar':
`--append', `--update', `--concatenate', `--delete', and `--compare'.

You are not likely to use these operations as frequently as those
covered in the last chapter; however, since they perform specialized
functions, they are quite useful when you do need to use them. We will
give examples using the same directory and files that you created in
the last chapter. As you may recall, the directory is called
`practice', the files are `jazz', `blues', `folk', `rock', and the two
archive files you created are `collection.tar' and `music.tar'.

We will also use the archive files `afiles.tar' and `bfiles.tar'.
`afiles.tar' contains the members `apple', `angst', and `aspic'.
`bfiles.tar' contains the members `./birds', `baboon', and `./box'.

Unless we state otherwise, all practicing you do and examples you
follow in this chapter will take place in the `practice' directory that
you created in the previous chapter; see *Note prepare for examples::.
(Below in this section, we will remind you of the state of the examples
where the last chapter left them.)

The five operations that we will cover in this chapter are:

`--append'
`-r'
Add new entries to an archive that already exists.

`--update'
`-r'
Add more recent copies of archive members to the end of an
archive, if they exist.

`--concatenate'
`--catenate'
`-A'
Add one or more pre-existing archives to the end of another
archive.

`--delete'
Delete items from an archive (does not work on tapes).

`--compare'
`--diff'
`-d'
Compare archive members to their counterparts in the file system.

File: tar.info, Node: append, Next: update, Prev: Operations, Up: Advanced tar

4.2.2 How to Add Files to Existing Archives: `--append'
-------------------------------------------------------

_(This message will disappear, once this node revised.)_

If you want to add files to an existing archive, you don't need to
create a new archive; you can use `--append' (`-r'). The archive must
already exist in order to use `--append'. (A related operation is the
`--update' operation; you can use this to add newer versions of archive
members to an existing archive. To learn how to do this with
`--update', *note update::.)

If you use `--append' (`-r') to add a file that has the same name as
an archive member to an archive containing that archive member, then the
old member is not deleted. What does happen, however, is somewhat
complex. `tar' _allows_ you to have infinite number of files with the
same name. Some operations treat these same-named members no
differently than any other set of archive members: for example, if you
view an archive with `--list' (`-t'), you will see all of those members
listed, with their modification times, owners, etc.

Other operations don't deal with these members as perfectly as you
might prefer; if you were to use `--extract' (`--get', `-x') to extract
the archive, only the most recently added copy of a member with the
same name as four other members would end up in the working directory.
This is because `--extract' extracts an archive in the order the
members appeared in the archive; the most recently archived members
will be extracted last. Additionally, an extracted member will
_replace_ a file of the same name which existed in the directory
already, and `tar' will not prompt you about this(1). Thus, only the
most recently archived member will end up being extracted, as it will
replace the one extracted before it, and so on.

There exists a special option that allows you to get around this
behavior and extract (or list) only a particular copy of the file.
This is `--occurrence' option. If you run `tar' with this option, it
will extract only the first copy of the file. You may also give this
option an argument specifying the number of copy to be extracted. Thus,
for example if the archive `archive.tar' contained three copies of file
`myfile', then the command

tar --extract --file archive.tar --occurrence=2 myfile

would extract only the second copy. *Note --occurrence: Option Summary,
for the description of `--occurrence' option.

If you want to replace an archive member, use `--delete' to delete
the member you want to remove from the archive, , and then use
`--append' to add the member you want to be in the archive. Note that
you can not change the order of the archive; the most recently added
member will still appear last. In this sense, you cannot truly
"replace" one member with another. (Replacing one member with another
will not work on certain types of media, such as tapes; see *Note
delete:: and *Note Media::, for more information.)

* Menu:

* appending files:: Appending Files to an Archive
* multiple::

---------- Footnotes ----------

(1) Unless you give it `--keep-old-files' option, or the disk copy
is newer than the the one in the archive and you invoke `tar' with
`--keep-newer-files' option

File: tar.info, Node: appending files, Next: multiple, Up: append

4.2.2.1 Appending Files to an Archive
.....................................

_(This message will disappear, once this node revised.)_

The simplest way to add a file to an already existing archive is the
`--append' (`-r') operation, which writes specified files into the
archive whether or not they are already among the archived files. When
you use `--append', you _must_ specify file name arguments, as there is
no default. If you specify a file that already exists in the archive,
another copy of the file will be added to the end of the archive. As
with other operations, the member names of the newly added files will
be exactly the same as their names given on the command line. The
`--verbose' (`-v') option will print out the names of the files as they
are written into the archive.

`--append' cannot be performed on some tape drives, unfortunately,
due to deficiencies in the formats those tape drives use. The archive
must be a valid `tar' archive, or else the results of using this
operation will be unpredictable. *Note Media::.

To demonstrate using `--append' to add a file to an archive, create
a file called `rock' in the `practice' directory. Make sure you are in
the `practice' directory. Then, run the following `tar' command to add
`rock' to `collection.tar':

$ tar --append --file=collection.tar rock

If you now use the `--list' (`-t') operation, you will see that `rock'
has been added to the archive:

$ tar --list --file=collection.tar
-rw-rw-rw- me user 28 1996-10-18 16:31 jazz
-rw-rw-rw- me user 21 1996-09-23