v7tar(1)
NAME
v7tar − tape archiver
SYNTAX
v7tar [ key ] [ name... ]
DESCRIPTION
The v7tar command saves and restores files on magtape or RX50 floppy diskette. Its actions are controlled by the key argument. The key is a string of characters containing at most one function letter and possibly one or more function modifiers. Other arguments to the command are file or directory names specifying which files are to be dumped or restored. In all cases, appearance of a directory name refers to the files and (recursively) subdirectories of that directory. The v7tar command also saves and restores special files.
KEYS
The function portion of the key is specified by one of the following letters:
r The named files are written on the end of the tape. The c function implies this. Writing files on the end of a v7tar tape creates a second archive on that tape. Using the r option with a tape where the second archive already exists will overwrite the second archive, not create a third archive. Dealing with the second archive can be clumsy, that is, the no rewind on close tape special file must be used to position the tape after the first archive. For example:
v7tar tf /dev/nrht0 >/dev/null
x The named files are extracted from the tape. If the named file matches a directory whose contents had been written onto the tape, this 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 tape is extracted. Note that if multiple entries specifying the same file are on the tape, the last one overwrites all earlier.
t The names of the specified files are listed each time they occur on the tape. If no file argument is given, all of the names on the tape are listed.
u The named files are added to the tape if either they are not already there or have been modified since last put on the tape. The files are appended to the end of the tape (see r above).
B Create a new tape; writing begins on the beginning of the tape instead of after the last file. This command implies r.
The following characters may be used in addition to the letter which selects the function desired.
0,...,7 This modifier selects the drive on which the tape is mounted. The default is 0.
v Normally v7tar does its work without any diagnostic output. The v (verbose) option causes it to type the name of each file it treats preceded by the function letter. With the t function, v gives more information about the tape entries than just the name.
w Causes v7tar to print the action to be taken followed by file name, then wait for user confirmation. If a word beginning with y is given, the action is performed. Any other input means don’t do it.
f Causes v7tar to use the next argument as the name of the archive instead of /dev/rmt? or /dev/rht?, for example, v7tar could archive to an RX50 floppy diskette with the command
v7tar cf /dev/rrx? files
If the name of the file is ’−’, v7tar writes to standard output or reads from standard input, whichever is appropriate. Thus, v7tar can be used as the head or tail of a filter chain The v7tar command can also be used to move hierarchies with the command
cd fromdir; v7tar cf - . | (cd todir; v7tar xf -)
b Causes v7tar to use the next argument as the blocking factor for tape records. The default is 1, the maximum is 20. This option should only be used with raw magnetic tape archives or with raw disk archives that will never be updated, for example, RX50 diskettes. The block size is determined automatically when reading tape and disk archives (key letters x and t), unless both the b and f keys are specified. In that case the blocking factor specified by the b key is used unconditionally.
l Tells v7tar to complain if it cannot resolve all of the links to the files dumped. If this is not specified, no error messages are printed.
m Tells v7tar to not restore the modification times. The mod time will be the time of extraction.
n Select (NRZI) 800 BPI density on the specified tape unit, /dev/rmt0 by default.
p Changes the mode of extracted files to the original mode, as written to tape. By default, the v7tar user’s mode is passed to the file.
o Suppress the normal directory information. On output, v7tar normally places information specifying owner and mode of directories. This allows v7tar to extract the files even if the top level directory does not exist.
d Selects the RX50 diskettes as the v7tar medium, /dev/rrx0 by default. In addition, the blocking factor is established as 10, unless otherwise specified.
RESTRICTIONS
There is no way to ask for the n-th occurrence of a file.
Tape errors are handled ungracefully.
The b option should not be used with archives that are going to be updated. The current magtape driver cannot backspace raw magtape. If the archive is on a disk file the b option should not be used at all, as updating an archive stored in this manner can destroy it. The b option may be used with raw disk archives if and only if those archives will never be updated.
The current limit on file name length is 100 characters.
Previous versions of v7tar will restore special files as empty regular files, and may return "cannot create" messages when extracting directory files.
DIAGNOSTICS
An error occurs if there is not enough memory available to hold the link tables.
FILES
/dev/rmt?
/dev/rht?
/dev/rrx?
/tmp/v7tar*