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Test Your Knowledge in Computers #146
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In 1983, Richard Stallman announced the GNU (short for "GNU's Not Unix") project, to create a proprietary, commercial software Unix-like system.
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tar(1) [opendarwin man page]

TAR(1)							    BSD General Commands Manual 						    TAR(1)

NAME
gnutar -- tape archiver; manipulate "tar" archive files SYNOPSIS
gnutar [[-]bundled-options Args] [gnu-style-flags] [filenames | -C directory-name] ... DESCRIPTION
Tar is short for ``tape archiver'', so named for historical reasons; the gnutar program creates, adds files to, or extracts files from an ar- chive file in gnutar format, called a tarfile. A tarfile is often a magnetic tape, but can be a floppy diskette or any regular disk file. The first argument word of the gnutar command line is usually a command word of bundled function and modifier letters, optionally preceded by a dash; it must contain exactly one function letter from the set A, c, d, r, t, u, x, for append, create, difference, replace, table of contents, update, and extract (further described below). The command word can also contain other function modifiers described below, some of which will take arguments from the command line in the order they are specified in the command word (review the EXAMPLES section). Functions and function modifiers can also be specified with the GNU argument convention (preceded by two dashes, one function or modifier per word. Command-line arguments that specify files to add to, extract from, or list from an archive may be given as shell pattern matching strings. FUNCTIONS
Exactly one of the following functions must be specified. -A --catenate --concatenate Append the contents of named file, which must itself be a gnutar archive, to the end of the archive (erasing the old end-of- archive block). This has the effect of adding the files contained in the named file to the first archive, rather than adding the second archive as an element of the first. Note: This option requires a rewritable tarfile, and therefore does not work on quarter-inch cartridge tapes. -c --create Create a new archive (or truncates an old one) and writes the named files to it. -d --diff --compare Find differences between files in the archive and corresponding files in the file system. --delete Delete named files from the archive. (Does not work on quarter-inch tapes). -r --append Append files to the end of an archive. (Does not work on quarter-inch tapes). -t --list List the contents of an archive; if filename arguments are given, only those files are listed, otherwise the entire table of contents is listed. -u --update Append the named files if the on-disk version has a modification date more recent than their copy in the archive (if any). Does not work on quarter-inch tapes. -x --extract --get Extract files from an archive. The owner, modification time, and file permissions are restored, if possible. If no file arguments are given, extract all the files in the archive. If a filename argument matches the name of a directory on the tape, that directory and its contents are extracted (as well as all directories under that directory). If the archive con- tains multiple entries corresponding to the same file (see the --append command above), the last one extracted will overwrite all earlier versions. OPTIONS
The other options to gnutar may be combined arbitrarily; single-letter options may be bundled in with the command word. Verbose options which take arguments will be followed by the argument; single-letter options will consume successive command line arguments (see the EXAMPLES below). gnutar will properly handle option arguments passed either with or without a leading `=` (i.e. either --option=arg or --option arg). --help Prints a message listing and briefly describing all the command options to gnutar. --atime-preserve Restore the access times on files which are written to tape (note that this will change the inode-change time!). -b --block-size number --blocking-factor number --record-size size Sets the block size for reading or writing to number * 512-byte blocks. Or sets block size for reading or writing to size bytes which must be a multiple of 512. -B --read-full-records Re-assemble short reads into full records (for reading 4.2BSD pipes). --backup control Backup files before removal. Optionally, the user can specify a control argument to control how gnutar performs the backups. Supported values are listed bellow in the ENVIRONMENT section. --suffix suffix Backup files before removal. Override the normal backup suffix (default: '~'), using suffix instead. -C directory --directory directory Change to directory before processing the remaining arguments. --checkpoint Print number of buffer reads/writes while reading/writing the archive. -f [hostname:]file --file [hostname:]file Read or write the specified file (default is /dev/sa0). If a hostname is specified, gnutar will use rmt(8) to read or write the specified file on a remote machine. ``-'' may be used as a filename, for reading or writing to/from stdin/stdout. --force-local Archive file is local even if it has a colon. -F file --info-script file --new-volume-script file Run a script at the end of each archive volume (implies -M). -G --incremental Create/list/extract old GNU-format incremental backup. -g file --listed-incremental file Create/list/extract new GNU-format incremental backup. --group name Force group as group for added files. -h --dereference Don't write symlinks as symlinks; write the data of the files they name. -i --ignore-zeros Ignore blocks of zeroes in archive (usually means End-Of-File). --ignore-failed-read Don't exit with non-zero status on unreadable files. -j --bzip2 Filter the archive through bzip2(1). -k --keep-old-files Keep files which already exist on disk; don't overwrite them from the archive. -K file --starting-file file Begin at file in the archive. -l --one-file-system Stay in local file system when creating an archive (do not cross mount points). -L number --tape-length number Change tapes after writing number * 1024 bytes. --mode changes Force changes to file mode of added files. -m --modification-time Don't extract file modified time. -M --multi-volume Create/list/extract multi-volume archive. --no-recursion Don't recurse into subdirectories when creating. --volno-file file File name with volume number to start with. -N date --after-date date --newer date Only store files with creation time newer than date. --newer-mtime date Only store files with modification time newer than date. --no-same-owner Do not preserve ownership when extracting files. Extract them all as owned by the current user. --no-same-permissions Do not extract permission information. Extract them using the default permissions for the current user. --numeric-owner Use numbers instead of names for owner/group names. -o --old-archive --portability Write a V7 format archive, rather than POSIX format. -O --to-stdout Extract files to standard output. --owner name Force name as owner for added files. --overwrite Overwrite existing files when extracting. --overwrite-dir Overwrite directory metadata when extracting. -p --same-permissions --preserve-permissions Extract all permission information. --preserve Has the effect of -p -s. -P --absolute-names Don't strip leading '/' from file names. --posix Instructs gnutar to create a POSIX compliant `tar' archive. -R --block-number Show record number within archive with each message. --remove-files Remove files after adding them to the archive. --rsh-command command Use command instead of rsh for remote archives/files. -s --same-order --preserve-order List of names to extract is sorted to match archive. --same-owner Try to preserve ownership when extracting files. --show-omitted-dirs Show directories which were omitted while processing the archive. -S --sparse Handle ``sparse'' files efficiently. -T file --files-from file Get names of files to extract or create from file, one per line. --null Modifies behavior of -T to expect null-terminated names; disables -C. --totals Prints total bytes written with --create. -U --unlink-first Unlink files before creating them. --recursive-unlink Empty hierarchies prior to extracting directory. -v --verbose Lists files written to archive with --create or extracted with --extract; lists file protection information along with file names with --list. -V volume-name --label volume-name Create archive with the given volume-name. When used with list or extract, volume-name is used as a globing pattern. --version Print gnutar program version number. -w --interactive --confirmation Ask for confirmation for every action. -W --verify Attempt to verify the archive after writing it. --exclude pattern Exclude files matching the pattern (don't extract them, don't add them, don't list them). -X file --exclude-from file Exclude files listed in file. --anchored Exclude patterns match file name start (default). --no-anchored Exclude patterns match after any /. --ignore-case Exclude patterns ignore case. --no-ignore-case Exclude patterns are case sensitive (default). --wildcards Exclude patterns use wildcards (default). --no-wildcards Exclude patterns are plain strings. --wildcards-match-slash Exclude pattern wildcards match '/' (default). --no-wildcards-match-slash Exclude pattern wildcards do not match '/'. -Z --compress --uncompress Filter the archive through compress(1). -z --gzip --ungzip --gunzip Filter the archive through gzip(1). --use-compress-program program Filter the archive through program (which must accept -d to mean ``decompress''). -[0-7][lmh] Specify tape drive and density. ENVIRONMENT
The gnutar program examines the following environment variables. POSIXLY_CORRECT Normally, gnutar will process flag arguments that appear in the file list. If set in the environment, this causes gnutar to consider the first non-flag argument to terminate flag processing, as per the POSIX specification. SHELL In interactive mode, a permissible response to the prompt is to request to spawn a subshell, which will be /bin/sh unless the SHELL variable is set. SIMPLE_BACKUP_SUFFIX Sets the backup suffix used by gnutar. Default is '~'. TAPE Changes gnutar's default tape drive (which is still overridden by the -f flag). TAR_OPTIONS The environment variable TAR_OPTIONS can hold a set of default options for gnutar. These options are interpreted first and can be overwritten by explicit command line parameters. TAR_RSH The TAR_RSH environment variable allows you to override the default shell used as the transport for gnutar. VERSION_CONTROL Sets the backup method used by gnutar. Possible values: t, numbered make numbered backups nil, existing numbered if numbered backups exist, simple otherwise never, simple always make simple backups Default behaviour is 'existing'. FILES
/dev/sa0 The default tape drive. EXAMPLES
To create an archive on tape drive /dev/sa0 with a block size of 20 blocks, containing files named bert and ernie, you can enter tar cfb /dev/sa0 20 bert ernie or tar --create --file /dev/sa0 --block-size 20 bert ernie Note that the -f and -b flags both require arguments, which they take from the command line in the order they were listed in the command word. Because /dev/sa0 is the default device, and 20 is the default block size, the above example could have simply been tar c bert ernie To extract all the C sources and headers from an archive named backup.tar, type tar xf backup.tar '*.[ch]' Note that the pattern must be quoted to prevent the shell from attempting to expand it according the files in the current working directory (the shell does not have access to the list of files in the archive, of course). To move file hierarchies, use a command line like this: tar -cf - -C srcdir . | tar xpf - -C destdir To create a compressed archive on diskette, using gzip(1), use a command-line like tar --block-compress -z -c -v -f /dev/fd1a -b 36 tar/ Note that you cannot mix bundled flags and --style flags; you can use single-letter flags in the manner above, rather than having to type tar --block-compress --gzip --verbose --file /dev/fd1a --block-size 20 tar/ The above-created diskette can be listed with tar tvfbz /dev/fd1a 36 To join two gnutar archives into a single archive, use tar Af archive1.tar archive2.tar which will add the files contained in archive2.tar onto the end of archive1.tar (note that this can't be done by simply typing cat archive2.tar >> archive1.tar because of the end-of-file block at the end of a gnutar archive). To archive all files from the directory srcdir, which were modified after Feb. 9th 1997, 13:00 h, use tar -c -f backup.tar --newer-mtime 'Feb 9 13:15 1997' srcdir/ Other possible time specifications are '02/09/97 13:15', '1997-02-09 13:15', '13:15 9 Feb 1997', '9 Feb 1997 13:15', 'Feb. 9, 1997 1:15pm', '09-Feb', '3 weeks ago' or 'May first Sunday'. To specify the correct time zone use either e.g. '13:15 CEST' or '13:15+200'. SEE ALSO
bzip2(1), compress(1), gzip(1), pax(1), rmt(8), info tar HISTORY
The gnutar format has a rich history, dating back to Sixth Edition UNIX. The current implementation of gnutar is the GNU implementation, which originated as the public-domain gnutar written by John Gilmore. AUTHORS
A cast of thousands, including [as listed in the ChangeLog file in the source] John Gilmore (author of original public domain version), Jay Fenlason (first GNU author), Joy Kendall, Jim Kingdon, David J. MacKenzie, Michael I Bushnell, Noah Friedman, and innumerable others who have contributed fixes and additions. Man page obtained by the FreeBSD group from the NetBSD 1.0 release. BUGS
The -C feature does not work like historical gnutar programs, and is probably untrustworthy. The -A command should work to join an arbitrary number of gnutar archives together, but it does not; attempting to do so leaves the end-of- archive blocks in place for the second and subsequent archives. The gnutar file format is a semi fixed width field format, and the field for device numbers were designed for 16 bit (8 major, 8 minor) and can not absorb our 32 bit (8 major, 16+8 minor) numbers. BSD
December 23, 2000 BSD