tar.1

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)tar.1	4.1	12/9/88
.TH tar 1
.SH Name
tar \- multivolume archiver
.SH Syntax
.B tar
[\|\fIkey\fR\|] [\|\fIname...\fR\|]
.SH Description
.NXA "tar command" "mdtar command"
.NXA "tar command" "ar program"
.NXAM "tar command" "tar file"
.NXR "tar command"
.NXR "file" "backing up"
The tape archiver command,
.PN tar ,
saves and restores multiple files to and from a single archive.
The default archive device is 
.PN /dev/rmt0h ,
but any file or device may be requested through the use of options.
.PP
The
.I key
is a string of characters containing at most one function
letter and possibly names specifying which files to dump or 
restore.
In all cases, appearance of a directory name refers to the files and
(recursively) subdirectories of that directory.
.PP
This utility supports EOT handling which allows the use of
multiple media.  The utility prompts for the next volume when it
encounters the end of the current volume.
.SH Function Keys
.NXR "tar command" "keys"
The function portion of the key is specified by one of
the following letters:
.TP 8
.B c
Create a new archive on tape, disk or file.
Writing starts at the beginning of the archive
instead of after the last file.
.TP 8
.B r
Write the named files to the end of the archive.
.TP 8
.B t
List the names of the files as they occur on the input archive.
.TP 8
.B u
Add the named files to the archive if they are not
there already or if they have been modified since they were
last put in the archive.
.TP 8
.B x
Extract the named files from the archive.
If the named file matches a directory whose contents
had been written into the archive,
the directory is recursively extracted.
The owner, modification time,
and mode are restored, if possible.
If no file argument is given, the entire content
of the archive is extracted.
Note that if multiple entries specifying the same
file are in the archive,
the last one overwrites all previous versions extracted.
.SH Options
.NXR "tar command" "options"
You can use one or more of the following options in
addition to the letter which selects the function
desired.
.TP 10
.B 0...9
Substitute number for the device unit number as in 
.PN /dev/rmt#h .
The default is the high density rewind
tape device number zero named 
.PN /dev/rmt0h .
The command 
.EX
tar cv4 tar.c
.EE
uses device 
.PN /dev/rmt4h .
.TP 10
.B A
Use next argument as archive number with which to begin output.
.TP 10
.B B
Force input and output blocking to 20 blocks/record. 
This option allows
.PN tar
to work across a communications channel where the blocking may not
be maintained.
.TP 10
.B D
Directory output in original 
.PN tar
style.
.TP 10
.B C
Use to perform a directory change prior to archiving data.
.TP 10
.B "\F[ F ]"
Operate in 
.I fast mode .
When
.B \-F
is specified,
.PN tar
skips all SCCS directories, core files, and error files.
When
.B \-FF
is specified,
.PN tar
also skips all
.PN a.out
and
.B *.o
files.
.TP 10
.B H
Help mode.
Print a summary of the function keys and options.
.TP 10
.B M
Next arg specifies maximum archive number to be written and
prints current archive number on output line.
.TP 10
.B N
No multi-archive, file splitting, or new header format on output.
Output directories in previous tar format. On input, set file
UID & GID from file header vs. values in 
.PN /etc/passwd
and group files.
.TP 10
.B O
Include file owner & group names in verbose output (t & x functions)
if present in archive header.  Output warning message if owner
or group name not found in
.PN /etc/passwd
or
.PN /etc/group
file (cru functions).
.TP 10
.B P
Used to specify POSIX format tapes.
Unnecessary with keys other than the \fBc\fR key.
.TP 10
.B R
Each named file contains a list of file names separated by newlines
which is added to (\fBc\fP function key) or extracted
from (\fBx\fP function key) the archive.
.TP 10
.B S
Output User Group Standard archive format.
.TP 10
.B V
Display extended verbose information.
Included are the version number of
.PN tar ,
the number of blocks used on the device,
the number of blocks in a file,
and the protection modes given in a format similar to the
.B ls
.B \-l
command.
In addition to this information,
.B V
provides the information given by the
.B v
option.
.TP 10
.B b
Use the next argument as the blocking factor for tape records.
The default is 20 (the maximum is 127).
This option should only be used with raw magnetic tape archives (See 
the
.B f
option).
The block size is determined automatically
when reading tapes (\fBx\fP and \fBt\fR)
keys. See the \fBRestrictions\fP section. 
.TP 10
.B d
Use 
.PN /dev/rra1a 
as the default device.
The 
.PN mdtar
command is recommended for use with floppy disks.
.TP 10
.B f
Use the next argument as the name of the archive instead of
/dev/rmt0h.
If the name of the file is
.B \- ,
.PN tar
writes to standard output or
reads from standard input,
whichever is appropriate.
Thus,
.PN tar
can be used as the head or tail of a filter chain.
You can also use
.PN tar
to move hierarchies.
The following example shows how to move the directory
.I fromdir
to the directory
.I todir :
.EX
# cd fromdir; tar cf \- . | (cd todir; tar xpf \-)
.EE
.TP
.B h
Save a copy of the actual file on the output device under the
symbolic link name,
instead of placing the symbolic information on the output.
The default action of
.PN tar
is to place symbolic link information on the output device.
A copy of the file itself is not saved on the output device.
.TP
.B i
Ignore checksum errors found in the archive.
.TP 10
.B l
Complain if
.PN tar
cannot resolve all of the links to the files dumped.
If this is not specified,
no error messages are printed.
.TP 10
.B m
Do not restore the modification times.
The modification time is the time of extraction.
Tar normally restores modification times of regular and
special files.
.TP 10
.B o
Suppress the normal directory information.  On output, 
.PN tar
normally places information specifying owner and modes of 
directories in the archive.  Former versions of 
.PN tar ,
when
encountering this information will give error message of the 
form,
.EX
<name>/: cannot create
.EE
.PN tar
will place information specifying owner and modes
of directories in the archive.
.TP 10
.B p
Restore the named files to their original modes,
ignoring the present 
.MS umask 2 .
Setuid and sticky bit information
is also restored to the superuser.
.TP 10
.B s
Next argument specifies size of archive in 512 byte blocks.
.TP 10
.B v
Write the name of each file treated,
preceded by the function letter,
to diagnostic output.  
Normally,
.PN tar
does its work silently.
With the
.B t
function key,
the verbose option provides more information about the
tape entries than just their names.
.EX
#cd /
#tar cvf tar-out vmunix
.EE
Produces the output ``a vmunix 1490 blocks'' where 1490 is the number of 512 byte
blocks in the file ``vmunix''.
.EX
#tar xvf tar-out
.EE
Produces the output ``x vmunix, 762880 bytes, 1490 blocks'' where 762880 is the
number of bytes and 1490 is the number of 512 byte blocks in the file ``vmunix''
which was extracted.
.TP 10
.B w
Print the action to be taken, followed by file name,
then wait for user confirmation.
If a word beginning with the letter
.B y
is given,
the action is done.
Any other input means do not do it.
.SH Restrictions
.NXR "tar command" "restricted"
There is no way to ask for the
.IR n\^\^th
occurrence of a file.
.PP
Tape errors are handled ungracefully.
.PP
The 
.B u
key can be slow.
.PP
The limit on file name length is 100 characters.
.PP
There is no way to follow symbolic links selectively.
.PP
On SCSI tape devices tar (when reading) may end on one volume 
of a multi-volume set
without prompting for the next volume. This is a very infrequent
condition. The next volume should be loaded and the command issued
again.
.PP
Using a blocking factor other than the default (\fBb\fP option) may lead 
to higher performance. However, you must select a value that is compatible 
with the hardware limitations of the source and destination machines. 
Software limitations may apply for other versions of 
.PN tar .
.PP
When extracting (\fBx\fP), 
.PN tar
reads the entire tape. See the \fBr\fP and \fBu\fP keys.
.SH Examples
.NXR(e) "tar command"
To archive files from 
.PN /usr/include
and 
.PN /etc ,
type:
.EX
# tar c \-C /usr/include . \-C /etc .
.EE
.PP
The
.PN tar
command can properly handle blocked archives.
.SH Diagnostics
.NXR "tar command" "diagnostics"
Indicates bad key characters and read/write errors.
.PP
Indicates if enough memory is not available to hold the link tables.
.SH Files
.br
.PN /dev/rmt0h
.br
.PN /dev/rra1a
.br
.PN /tmp/tar*
.SH See Also
mdtar(1), mt(1), tar(5)