|PAX(1)||General Commands Manual||PAX(1)|
pax — read and
write file archives and copy directory hierarchies
pax will read, write, and list the members
of an archive file and will copy directory hierarchies.
pax operation is independent of the specific archive
format and supports a wide variety of different archive formats. A list of
supported archive formats can be found under the description of the
The presence of the
-r and the
-w options specifies which of the following
pax will operate under:
list, read, write, and
paxwill write to standard output a table of contents of the members of the archive file read from standard input, whose pathnames match the specified pattern arguments. The table of contents contains one filename per line and is written using single line buffering.
paxextracts the members of the archive file read from the standard input, with pathnames matching the specified pattern arguments. The archive format and blocking is automatically determined on input. When an extracted file is a directory, the entire file hierarchy rooted at that directory is extracted. All extracted files are created relative to the current file hierarchy. The setting of ownership, access and modification times, and file mode of the extracted files are discussed in more detail under the
paxwrites an archive containing the file operands to standard output using the specified archive format. When no file operands are specified, a list of files to copy with one per line is read from standard input. When a file operand is also a directory, the entire file hierarchy rooted at that directory will be included.
paxcopies the file operands to the destination directory. When no file operands are specified, a list of files to copy with one per line is read from the standard input. When a file operand is also a directory the entire file hierarchy rooted at that directory will be included. The effect of the copy is as if the copied files were written to an archive file and then subsequently extracted, except that there may be hard links between the original and the copied files (see the
Warning: The destination directory must not be one of the file operands or a member of a file hierarchy rooted at one of the file operands. The result of a copy under these conditions is unpredictable.
While processing a damaged archive during a read
or list operation,
attempt to recover from media defects and will search through the archive to
locate and process the largest number of archive members possible (see the
-E option for more details on error handling).
The directory operand specifies a
destination directory pathname. If the directory
operand does not exist, or it is not writable by the user, or it is not of
pax will exit with a non-zero exit
The pattern operand is used to select one or
more pathnames of archive members. Archive members are selected using the
pattern matching notation described by
glob(3). When the
pattern operand is not supplied, all members of the
archive will be selected. When a pattern matches a
directory, the entire file hierarchy rooted at that directory will be
selected. When a pattern operand does not select at
least one archive member,
pax will write these
pattern operands in a diagnostic message to standard
error and then exit with a non-zero exit status.
The file operand specifies the pathname of a
file to be copied or archived. When a file operand
does not select at least one archive member,
will write these file operand pathnames in a
diagnostic message to standard error and then exit with a non-zero exit
The options are as follows:
\0’) character as a pathname terminator, instead of newline (‘
\n’). This applies only to the pathnames read from standard input in the write and copy modes, and to the pathnames written to standard output in list mode. This option is expected to be used in concert with the
-print0function in find(1) or the
-0flag in xargs(1).
-xoption, the format currently being used in the archive will be selected. Any attempt to append to an archive in a format different from the format already used in the archive will cause
paxto exit immediately with a non-zero exit status. The blocking size used in the archive volume where writing starts will continue to be used for the remainder of that archive volume.
Warning: Many storage devices are not able to support the operations necessary to perform an append operation. Any attempt to append to an archive stored on such a device may damage the archive or have other unpredictable results. Tape drives in particular are more likely to not support an append operation. An archive stored in a regular file system file or on a disk device will usually support an append operation.
k’, or ‘
b’ to specify multiplication by 1048576 (1M), 1024 (1K) or 512, respectively. A pair of bytes limits can be separated by ‘
x’ to indicate a product.
Warning: Only use this option when writing an archive to a device which supports an end of file read condition based on last (or largest) write offset (such as a regular file or a tape drive). The use of this option with a floppy or hard disk is not recommended.
k’ or ‘
b’ to specify multiplication by 1024 (1K) or 512, respectively. A pair of blocksizes can be separated by ‘
x’ to indicate a product. A specific archive device may impose additional restrictions on the size of blocking it will support. When blocking is not specified, the default blocksize is dependent on the specific archive format being used (see the
-uoption, except that the file inode change time is checked instead of the file modification time. The file inode change time can be used to select files whose inode information (e.g., UID, GID, etc.) is newer than a copy of the file in the destination directory.
paxwill attempt to recover from an archive read error and will continue processing starting with the next file stored in the archive. A limit of 0 will cause
paxto stop operation after the first read error is detected on an archive volume. A limit of
paxto attempt to recover from read errors forever. The default limit is a small positive number of retries.
Warning: Using this option with
NONE should be used with extreme caution as
pax may get stuck in an infinite loop on a very
badly flawed archive.
paxwill prompt for the pathname of the file or device of the next volume in the archive.
#, a numeric GID. A ‘
\’ can be used to escape the
-Goptions may be supplied and checking stops with the first match.
paxwill prompt to /dev/tty giving the name of the file, its file mode, and its modification time.
paxwill then read a line from /dev/tty. If this line is blank, the file or archive member is skipped. If this line consists of a single period, the file or archive member is processed with no modification to its name. Otherwise, its name is replaced with the contents of the line.
paxwill immediately exit with a non-zero exit status if
EOFis encountered when reading a response or if /dev/tty cannot be opened for reading and writing.
-w), hard links are made between the source and destination file hierarchies whenever possible.
-dis also specified).
paxwill not prompt for a new volume. This option can be useful for automated tasks where error recovery cannot be performed by a human.
-x. In general, options take the form: name=value.
The following options are available for the old BSD tar format:
p. Multiple characteristics can be concatenated within the same string and multiple
-poptions can be specified. The meanings of the specification characters are as follows:
eflag is the sum of the
In the preceding list, ‘preserve’
indicates that an attribute stored in the archive is given to the
extracted file, subject to the permissions of the invoking process.
Otherwise the attribute of the extracted file is determined as part of
the normal file creation action. If neither the
e nor the
specification character is specified, or the user ID and group ID are
not preserved for any reason,
pax will not set
bits of the file mode. If the preservation of any of these items fails
for any reason,
pax will write a diagnostic
message to standard error. Failure to preserve these items will affect
the final exit status, but will not cause the extracted file to be
deleted. If the file characteristic letters in any of the string
option-arguments are duplicated or conflict with each other, the one(s)
given last will take precedence. For example, if
-p eme is specified, file
modification times are still preserved.
S_IRWXOas the mode argument. When the selected archive format supports the specification of linked files and these files cannot be linked while the archive is being extracted,
paxwill write a diagnostic message to standard error and exit with a non-zero exit status at the completion of operation.
The format of these regular expressions is:
As in ed(1),
old is a basic regular expression (see
new can contain an ampersand
n is a digit) back-references, or subexpression
matching. The old string may also contain newline
characters. Any non-null character can be used as a delimiter
/’ is shown here). Multiple
-s expressions can be specified. The expressions
are applied in the order they are specified on the command line,
terminating with the first successful substitution.
The optional trailing
g continues to
apply the substitution expression to the pathname substring, which
starts with the first character following the end of the last successful
substitution. The first unsuccessful substitution stops the operation of
g option. The optional trailing
p will cause the final result of a successful
substitution to be written to standard error in the following
File or archive member names that substitute to the empty string are not selected and will be skipped.
The dates specified by from_date to to_date are inclusive. If only a from_date is supplied, all files with a modification or inode change time equal to or younger are selected. If only a to_date is supplied, all files with a modification or inode change time equal to or older will be selected. When the from_date is equal to the to_date, only files with a modification or inode change time of exactly that time will be selected.
pax is in the
write or copy mode, the optional
trailing field [
can be used to determine which file time (inode change, file
modification or both) are used in the comparison. If neither is
specified, the default is to use file modification time only. The
m specifies the comparison of file modification
time (the time when the file was last written). The
c specifies the comparison of inode change time
(the time when the file inode was last changed; e.g., a change of owner,
group, mode, etc). When
m are both specified, then the modification and
inode change times are both compared.
The inode change time comparison is useful in selecting files
whose attributes were recently changed or selecting files which were
recently created and had their modification time reset to an older time
(as what happens when a file is extracted from an archive and the
modification time is preserved). Time comparisons using both file times
is useful when
pax is used to create a time
based incremental archive (only files that were changed during a
specified time range will be archived).
A time range is made up of six different fields and each field must contain two digits. The format is:
Where cc is the first two digits of the year (the century), yy is the last two digits of the year, the first mm is the month (from 01 to 12), dd is the day of the month (from 01 to 31), HH is the hour of the day (from 00 to 23), MM is the minute (from 00 to 59), and SS is the seconds (from 00 to 59). The minute field MM is required, while the other fields are optional and must be added in the following order: HH, dd, mm, yy, cc.
The SS field may be added independently
of the other fields. Time ranges are relative to the current time, so
-T 1234/cm would select all files with a
modification or inode change time of 12:34 PM today or later. Multiple
-T time range can be supplied and checking stops
with the first match.
paxto be the same as they were before being read or accessed by
#, a numeric UID. A ‘
\’ can be used to escape the
-Uoptions may be supplied and checking stops with the first match.
-loption. For pathnames representing a hard link to a previous member of the archive, the output has the format:
ls -l listing
For pathnames representing a symbolic link, the output has the format:
ls -l listing
Where ls -l listing is the output format
specified by the ls(1)
utility when used with the
-l option. Otherwise
for all the other operational modes (read,
copy), pathnames are written and flushed to standard
error without a trailing newline as soon as processing begins on that
file or archive member. The trailing newline is not buffered and is
written only after the file has been read or written.
st_devfield as described in stat(2) for more information about device IDs.
paxcurrently supports the following formats:
paxand is repaired.
paxand is repaired.
paxand is repaired.
paxand is repaired.
-ooption can be used when writing an archive to omit the storage of directories. This option takes the form:
pax will detect and report any file
that it is unable to store or extract as the result of any specific
archive format restrictions. The individual archive formats may impose
additional restrictions on use. Typical archive format restrictions
include (but are not limited to): file pathname length, file size, link
pathname length, and the type of the file.
-Doption, except that the inode change time is checked using the pathname created after all the file name modifications have completed.
-uoption, except that the modification time is checked using the pathname created after all the file name modifications have completed.
The options that operate on the names of files or archive members
-Z) interact as follows.
When extracting files during a read operation,
archive members are ‘selected’, based only on the user
specified pattern operands as modified by the
-U options. Then any
-i options will
modify in that order, the names of these selected files. Then the
-Z options will be
applied based on the final pathname. Finally, the
option will write the names resulting from these modifications.
When archiving files during a write operation,
or copying files during a copy operation, archive members
are ‘selected’, based only on the user specified pathnames as
modified by the
-U options (the
-D option only applies during a copy operation).
will modify in that order, the names of these selected files. Then during a
copy operation the
-Y and the
-Z options will be applied based on the final
pathname. Finally, the
-v option will write the
names resulting from these modifications.
When one or both of the
-D options are specified along with the
-n option, a file is not considered selected unless
it is newer than the file to which it is compared.
pax utility exits with one of the
Copy the contents of the current directory to the device /dev/rst0:
$ pax -w -f /dev/rst0 .
Give the verbose table of contents for an archive stored in filename:
$ pax -v -f filename
This sequence of commands will copy the entire olddir directory hierarchy to newdir:
$ mkdir newdir $ cd olddir $ pax -rw . ../newdir
Extract files from the archive a.pax. Files rooted in /usr are extracted relative to the current working directory; all other files are extracted to their unmodified path.
$ pax -r -s ',^/usr/,,' -f a.pax
This can be used to interactively select the files to copy from the current directory to dest_dir:
$ pax -rw -i . dest_dir
Extract all files from the archive a.pax which are owned by root with group bin and preserve all file permissions:
$ pax -r -pe -U root -G bin -f a.pax
Update (and list) only those files in the destination directory /backup which are older (less recent inode change or file modification times) than files with the same name found in the source file tree home:
$ pax -r -w -v -Y -Z home /backup
pax cannot create a file or a
link when reading an archive or cannot find a file when writing an archive,
or cannot preserve the user ID, group ID, or file mode when the
-p option is specified, a diagnostic message is
written to standard error and a non-zero exit status will be returned, but
processing will continue. In the case where
cannot create a link to a file,
pax will not create
a second copy of the file.
If the extraction of a file from an archive is prematurely
terminated by a signal or error,
pax may have only
partially extracted a file the user wanted. Additionally, the file modes of
extracted files and directories may have incorrect file bits, and the
modification and access times may be wrong.
If the creation of an archive is prematurely terminated by a
signal or error,
pax may have only partially created
the archive, which may violate the specific archive format
If while doing a copy,
pax detects a file is about to overwrite itself, the
file is not copied, a diagnostic message is written to standard error and
pax completes it will exit with a non-zero exit
pax utility is compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
The flags [
-0BDEGjOPTUYZz], the archive
formats bcpio, sv4cpio,
sv4crc, tar, and the flawed archive
handling during list and read operations
are extensions to that specification.
Keith Muller at the University of California, San Diego.
|September 19, 2010||OpenBSD-5.1|