This is tar.info, produced by Makeinfo version 3.12f from tar.texi. START-INFO-DIR-ENTRY * tar: (tar). Making tape (or disk) archives. END-INFO-DIR-ENTRY This file documents GNU `tar', a utility used to store, backup, and transport files. Copyright (C) 1992, 1994, 1995, 1996, 1997, 1999 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. This file documents GNU `tar', which is a utility used to store, backup, and transport files. `tar' is a tape (or disk) archiver. This manual documents the release 1.13. File: tar.info, Node: Top, Next: Introduction, Prev: (dir), Up: (dir) * Menu: * Introduction:: * Tutorial:: * tar invocation:: * operations:: * Backups:: * Choosing:: * Date input formats:: * Formats:: * Media:: * 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 * posix compliance:: * 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:: * extract options:: * backup:: * Applications:: * looking ahead:: Advanced GNU `tar' Operations * Operations:: * current state:: * 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 `--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:: * Ignore Failed Read:: Changing How `tar' Writes Files * Prevention Overwriting:: * Keep Old Files:: * Unlink First:: * Recursive Unlink:: * Modification Times:: * Setting Access Permissions:: * Writing to Standard Output:: * remove files:: Options to Prevent Overwriting Files * Keep Old Files:: * Unlink First:: * Recursive Unlink:: 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 * backup-specs example:: An Example Text of `Backup-specs' * Script Syntax:: Syntax for `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 * problems with exclude:: Crossing Filesystem Boundaries * directory:: Changing Directory * absolute:: Absolute File Names Date input formats * General date syntax:: Common rules. * Calendar date item:: 19 Dec 1994. * Time of day item:: 9:20pm. * Timezone item:: EST, DST, BST, UCT, AHST, ... * Day of week item:: Monday and others. * Relative item in date strings:: next tuesday, 2 years ago. * Pure numbers in date strings:: 19931219, 1440. * Authors of getdate:: Bellovin, 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 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 File: tar.info, Node: Introduction, Next: Tutorial, Prev: Top, Up: Top Introduction ************ Welcome to the GNU `tar' manual. GNU `tar' is used to create and manipulate files ("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. * Menu: * Book Contents:: What this Book Contains * Definitions:: Some Definitions * What tar Does:: What `tar' Does * Naming tar Archives:: How `tar' Archives are Named * posix compliance:: * Authors:: GNU `tar' Authors * Reports:: Reporting bugs or suggestions File: tar.info, Node: Book Contents, Next: Definitions, Prev: Introduction, Up: Introduction 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 the 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 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 peformed using `tar'. File: tar.info, Node: What tar Does, Next: Naming tar Archives, Prev: Definitions, Up: Introduction 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: posix compliance, Prev: What tar Does, Up: Introduction 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: posix compliance, Next: Authors, Prev: Naming tar Archives, Up: Introduction POSIX Compliance ================ We make some of our recommendations throughout this book for one reason in addition to what we think of as "good sense". The main additional reason for a recommendation is to be compliant with the POSIX standards. If you set the shell environment variable `POSIXLY_CORRECT', GNU `tar' will force you to adhere to these standards. Therefore, if this variable is set and you violate one of the POSIX standards in the way you phrase a command, for example, GNU `tar' will not allow the command and will signal an error message. You would then have to reorder the options or rephrase the command to comply with the POSIX standards. There is a chance in the future that, if you set this environment variable, your archives will be forced to comply with POSIX standards, also. No GNU `tar' extensions will be allowed. File: tar.info, Node: Authors, Next: Reports, Prev: posix compliance, Up: Introduction 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, and finally Franc,ois Pinard, 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 draft has been distributed in `tar' versions 1.04 (or even before?) through 1.10, then 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::. File: tar.info, Node: Reports, Prev: Authors, Up: Introduction Reporting bugs or suggestions ============================= If you find problems or have suggestions about this program or manual, please report them to `tar-bugs@gnu.org'. File: tar.info, Node: Tutorial, Next: tar invocation, Prev: Introduction, Up: Top 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: * 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:: File: tar.info, Node: assumptions, Next: stylistic conventions, Prev: Tutorial, Up: Tutorial 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, the differences between relative and absolute path names, and . * 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 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'. When we have lines which are too long to be displayed in any other way, we will show them like this: This is an example of a line which would otherwise not fit in this space. File: tar.info, Node: basic tar options, Next: frequent operations, Prev: stylistic conventions, Up: Tutorial 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 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 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, Prev: Two Frequent Options, 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 specfiy 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 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, Prev: create, Up: create 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 a file 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 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 are in the archive, they are called _archive members_, not files . 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 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 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'; *note posix compliance::. for more information on this.) File: tar.info, Node: create dir, Prev: short create, Up: create 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, 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 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, Prev: list, Up: list Listing the Contents of a Stored Directory ------------------------------------------ _(This message will disappear, once this node revised.)_ 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 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:: * failing commands:: File: tar.info, Node: extracting archives, Next: extracting files, Prev: extract, Up: extract 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 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::.). If you give the `--verbose' (`-v') option, then `--extract' (`--get', `-x') will print the names of the archive members as it extracts them.