Store, list or extract files in an archive (originally on tape – Tape ARchiver).
Syntax tar [[-]function] [options] filenames... tar [[-]function] [options] -C directory-name... Command-line arguments that specify files to add to, extract from, or list from an archive can be given as shell pattern matching strings. Functions: Exactly one of the following functions (shown in bold) 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. (see notes below) -c --create Create a new archive (or truncate an old one) and write 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. --test-label test the archive volume label and exit -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 direc- tory). If the archive contains multiple entries corre- sponding to the same file (see the --append command above), the last one extracted will overwrite all earlier versions. -C, --directory=DIR change to directory DIR -f, --file=ARCHIVE use archive file or device ARCHIVE -j, --bzip2 filter the archive through bzip2 -J, --xz filter the archive through xz -p, --preserve-permissions extract information about file permissions (default for superuser) -v, --verbose verbosely list files processed. -z, --gzip filter the archive through gzip
You can specify an argument for `–file (or -f ) 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 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’ (or `-f ARCHIVE-NAME’) when writing your `tar’ commands.
--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 might 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.
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.
--absolute-names -P Normally when creating an archive, `tar' strips an initial `/' from member names. This option disables that behavior. --after-date (See --newer.) --atime-preserve Tells `tar' to preserve the access time field in a file's inode when dumping it. --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 -I 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. --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. --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. --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-failed-read Instructs `tar' to exit successfully if it encounters an unreadable file. --ignore-umask (See --preserve-permissions'; *note Writing::..) --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. --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. --interactive --confirmation -w Specifies that `tar' should ask the user for confirmation before performing potentially destructive options, such as overwriting files. --keep-old-files -k When extracting files from an archive, `tar' will not overwrite existing files if this option is present. *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) --newer=DATE --after-date=DATE -N When creating an archive, `tar' will only add files that have changed since DATE. --newer-mtime In conjunction with --newer', `tar' will only add files whose contents have changed (as opposed to just --newer', which will also back up files for which any status information has changed). --no-recursion With this option, `tar' will not recurse into directories unless a directory is explicitly named as an argument to `tar'. --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. --old-archive (See --portability.) --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. --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. --portability --old-archive -o Tells `tar' to create an archive that is compatible with Unix V7 `tar'. --posix Instructs `tar' to create a POSIX compliant `tar' archive. --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. --recursive-unlink Similar to the --unlink-first option, removing 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. --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. --same-permissions (See --preserve-permissions; *note Writing::..) --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::. --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 Direct `tar' to remove the corresponding file from the file system before extracting it from the archive. *Note Writing::. --use-compress-program=PROG Instruct `tar' to access the archive through PROG, which is presumed to be a compression program of some sort. --verbose -v Be more verbose about the operation. This option can be specified multiple times (for some operations) to increase the amount of information displayed. --verify -W Verify that the archive was correctly written. --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.
Create a tar and zip the file (using the create function)
tar -czvf MyArchive Source_file or tar --create --gzip --verbose --file=MyArchive.gz Source_file
Extract the zip file created above:
tar -xzvf MyArchive Destination_file or tar --extract --gunzip --verbose --file=MyArchive.gz Destination_file
Extract a file, autodetecting the format, in this case an xz archive:
tar -xf some.tar.xz or tar --extract --file=some.tar.xz
Create a tar in zip format with the file named as todays date/time:
tar czvf my_backup.$(date +%Y%m%d-%H%M%S).tgz /users/simon
A simple shell script for the above:
#!/bin/bash tar czvf $1.$(date +%Y%m%d-%H%M%S).tgz $1 exit $?
Save the script as ‘arc’, use chmod to make it executable and then run it passing a single file or foldername:
chmod 700 arc ./arc /users/simon
Always tar -t before tar -x to check if the archive contents have been placed inside one subdirectory or will just spill all over the current directory.
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.
Related linux commands:
cpio – Copy files to and from archives.
gzip – Compress or decompress named file(s)
sum – Print a checksum for a file
unshar – Unpack shell archive scripts
xz – Compress or decompress .xz and .lzma files
zip – Package and compress (archive) files.
Equivalent Windows command: ZIP – compress files