PAX(1) BSD General Commands Manual PAX(1)
NAME
pax -- read and write file archives and copy directory hierarchies
SYNOPSIS
pax [-0cdnvz] [-f archive] [-s replstr] ... [-U user] ... [-G group] ... [-T [from_date] [,to_date]]
... [pattern ...]
pax -r [-cdiknuvzDYZ] [-f archive] [-o options] ... [-p string] ... [-s replstr] ... [-E limit]
[-U user] ... [-G group] ... [-T [from_date] [,to_date]] ... [pattern ...]
pax -w [-0dituvzHLPX] [-b blocksize] [[-a] [-f archive]] [-x format] [-s replstr] ... [-o options] ...
[-U user] ... [-G group] ... [-B bytes] [-T [from_date] [,to_date] [/[c][m]]] ... [file ...]
pax -r -w [-0diklntuvDHLPXYZ] [-p string] ... [-s replstr] ... [-U user] ... [-G group] ... [-T
[from_date] [,to_date] [/[c][m]]] ... [file ...] directory
DESCRIPTION
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 -x
option.
The presence of the -r and the -w options specifies which of the following functional modes pax will
operate under: list, read, write, and copy.
<none> List. pax will write to standard output a table of contents of the members of the archive file
read from standard input, whose pathnames match the specified patterns. The table of contents
contains one filename per line and is written using single line buffering.
-r Read. pax extracts the members of the archive file read from the standard input, with path-names pathnames
names matching the specified patterns. The archive format and blocking is automatically deter-mined determined
mined 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 -p option.
-w Write. pax writes an archive containing the file operands to standard output using the speci-fied specified
fied 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.
-r -w Copy. pax copies 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 -l option below).
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, pax will 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 type directory, pax will exit with a non-zero
exit status.
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 fnmatch(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, pax will write these file operand pathnames in a diagnostic
message to standard error and then exit with a non-zero exit status.
The options are as follows:
-0 Use the NUL (`\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 path-names pathnames
names written to standard output in list mode. This option is expected to be used in concert
with the -print0 function in find(1) or the -0 flag in xargs(1).
-a Append files to the end of an archive that was previously written. If an archive format is not
specified with a -x option, 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 pax to 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.
-B bytes
Limit the number of bytes written to a single archive volume to bytes. The bytes limit can end
with `m', `k', or `b' to specify multiplication by 1048576 (1M), 1024 (1K) or 512, respec-tively. respectively.
tively. 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.
-b blocksize
When writing an archive, block the output at a positive decimal integer number of bytes per
write to the archive file. The blocksize must be a multiple of 512 bytes with a maximum of
64512 bytes. Archives larger than 32256 bytes violate the POSIX standard and will not be por-table portable
table to all systems. A blocksize can end with `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 -x option).
-c Match all file or archive members except those specified by the pattern and file operands.
-D This option is the same as the -u option, 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 destina-tion destination
tion directory.
-d Cause files of type directory being copied or archived, or archive members of type directory
being extracted, to match only the directory file or archive member and not the file hierarchy
rooted at the directory.
-E limit
Limit the number of consecutive read faults while trying to read a flawed archive to limit.
With a positive limit, pax will 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 pax to
stop operation after the first read error is detected on an archive volume. A limit of NONE
will cause pax to 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.
-f archive
Specify archive as the pathname of the input or output archive, overriding the default standard
input (for list and read) or standard output (for write). A single archive may span multiple
files and different archive devices. When required, pax will prompt for the pathname of the
file or device of the next volume in the archive.
-G group
Select a file based on its group name, or when starting with a #, a numeric gid. A `\' can be
used to escape the #. Multiple -G options may be supplied and checking stops with the first
match.
-H Follow only command-line symbolic links while performing a physical file system traversal.
-i Interactively rename files or archive members. For each archive member matching a pattern op-erand operand
erand or each file matching a file operand, pax will prompt to /dev/tty giving the name of the
file, its file mode, and its modification time. pax will 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. pax will immediately exit with a non-zero
exit status if EOF is encountered when reading a response or if /dev/tty cannot be opened for
reading and writing.
-k Do not overwrite existing files.
-L Follow all symbolic links to perform a logical file system traversal.
-l (The lowercase letter ``ell.'') Link files. In the copy mode (-r -w), hard links are made
between the source and destination file hierarchies whenever possible.
-n Select the first archive member that matches each pattern operand. No more than one archive
member is matched for each pattern. When members of type directory are matched, the file hier-archy hierarchy
archy rooted at that directory is also matched (unless -d is also specified).
-O Force the archive to be one volume. If a volume ends prematurely, pax will not prompt for a
new volume. This option can be useful for automated tasks where error recovery cannot be per-formed performed
formed by a human.
-o options
Information to modify the algorithm for extracting or writing archive files which is specific
to the archive format specified by -x. In general, options take the form: name=value.
If the "-x pax" option is used, the ":=" form of keyword specification is supported. Also, the
following new keywords are implemented:
oo delete=<pattern>
oo exthdr.name=<string>
oo globexhdr.name=<string>
oo invalid=<action> for actions bypass, rename, utf-8 (recognized, but ignored), and write
oo linkdata
oo listopt=<format> for the 'F' conversion specifier (not the 'D', 'T', 'M', or 'L' speci-fiers) specifiers)
fiers)
oo times
oo all keywords in pax Extended Header, with the following restrictions:
charset keyword recognized, but ignored
realtime.any keyword not recognized
security.any keyword not recognized
In "copy mode", only the following new keywords are supported:
oo delete=
oo invalid=
oo path= (from pax Extended Header description)
-P Do not follow symbolic links, perform a physical file system traversal. This is the default
mode.
-p string
Specify one or more file characteristic options (privileges). The string option-argument is a
string specifying file characteristics to be retained or discarded on extraction. The string
consists of the specification characters a, e, m, o, and p. Multiple characteristics can be
concatenated within the same string and multiple -p options can be specified. The meanings of
the specification characters are as follows:
a Do not preserve file access times. By default, file access times are preserved whenever
possible.
e `Preserve everything', the user ID, group ID, file mode bits, file access time, and file
modification time. This is intended to be used by root, someone with all the appropriate
privileges, in order to preserve all aspects of the files as they are recorded in the ar-chive. archive.
chive. The e flag is the sum of the o and p flags.
m Do not preserve file modification times. By default, file modification times are preserved
whenever possible.
o Preserve the user ID and group ID.
p `Preserve' the file mode bits. This is intended to be used by a user with regular privi-leges privileges
leges who wants to preserve all aspects of the file other than the ownership. The file
times are preserved by default, but two other flags are offered to disable this and use the
time of extraction instead.
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 o specification character is specified, or the user ID and group ID are
not preserved for any reason, pax will not set the S_ISUID (setuid) and S_ISGID (setgid) 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 character-istic characteristic
istic 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.
-r Read an archive file from standard input and extract the specified files. If any intermediate
directories are needed in order to extract an archive member, these directories will be created
as if mkdir(2) was called with the bitwise inclusive OR of S_IRWXU, S_IRWXG, and S_IRWXO as 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, pax will write a diagnostic
message to standard error and exit with a non-zero exit status at the completion of operation.
-s replstr
Modify the file or archive member names specified by the pattern or file operands according to
the substitution expression replstr, using the syntax of the ed(1) utility regular expressions.
The format of these regular expressions is:
/old/new/[gp]
As in ed(1), old is a basic regular expression and new can contain an ampersand (`&'), `\n'
(where n is a digit) back-references, or subexpression matching. The old string may also con-tain contain
tain 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 sub-string, substring,
string, which starts with the first character following the end of the last successful substi-tution. substitution.
tution. The first unsuccessful substitution stops the operation of the g option. The optional
trailing p will cause the final result of a successful substitution to be written to standard
error in the following format:
<original pathname> >> <new pathname>
File or archive member names that substitute to the empty string are not selected and will be
skipped.
-T [from_date][,to_date][/[c][m]]
Allow files to be selected based on a file modification or inode change time falling within a
specified time range of from_date to to_date (the dates 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 modifi-cation modification
cation or inode change time of exactly that time will be selected.
When pax is in the write or copy mode, the optional trailing field [c][m] can be used to deter-mine determine
mine 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 speci-fies specifies
fies 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 c and 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:
[[[[[cc]yy]mm]dd]HH]MM[.SS]
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.
-t Reset the access times of any file or directory read or accessed by pax to be the same as they
were before being read or accessed by pax.
-U user
Select a file based on its user name, or when starting with a #, a numeric UID. A `\' can be
used to escape the #. Multiple -U options may be supplied and checking stops with the first
match.
-u Ignore files that are older (having a less recent file modification time) than a pre-existing
file or archive member with the same name. During read, an archive member with the same name
as a file in the file system will be extracted if the archive member is newer than the file.
During write, a file system member with the same name as an archive member will be written to
the archive if it is newer than the archive member. During copy, the file in the destination
hierarchy is replaced by the file in the source hierarchy or by a link to the file in the
source hierarchy if the file in the source hierarchy is newer.
-v During a list operation, produce a verbose table of contents using the format of the ls(1)
utility with the -l option. For pathnames representing a hard link to a previous member of the
archive, the output has the format:
<ls -l listing> == <link name>
For pathnames representing a symbolic link, the output has the format:
<ls -l listing> => <link name>
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, write, and 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.
-w Write files to the standard output in the specified archive format. When no file operands are
specified, standard input is read for a list of pathnames with one per line without any leading
or trailing <blanks>.
-X When traversing the file hierarchy specified by a pathname, do not descend into directories
that have a different device ID. See the st_dev field as described in stat(2) for more infor-mation information
mation about device IDs.
-x format
Specify the output archive format, with the default format being ustar. pax currently supports
the following formats:
bcpio The old binary cpio format. The default blocksize for this format is 5120 bytes.
This format is not very portable and should not be used when other formats are avail-able. available.
able. Inode and device information about a file (used for detecting file hard links
by this format), which may be truncated by this format, is detected by pax and is
repaired.
cpio The extended cpio interchange format specified in the IEEE Std 1003.2 (``POSIX.2'')
standard. The default blocksize for this format is 5120 bytes. Inode and device
information about a file (used for detecting file hard links by this format), which
may be truncated by this format, is detected by pax and is repaired.
pax "pax interchange format", described in the EXTENDED DESCRIPTION of the pax interchange
format in The Open Group's SUSv3 specification. Includes support for pax Header
Block, pax Extended Header, pax Extended Header Keyword Precedence, and pax Extended
Header File Times.
sv4cpio The System V release 4 cpio. The default blocksize for this format is 5120 bytes.
Inode and device information about a file (used for detecting file hard links by this
format), which may be truncated by this format, is detected by pax and is repaired.
sv4crc The System V release 4 cpio with file crc checksums. The default blocksize for this
format is 5120 bytes. Inode and device information about a file (used for detecting
file hard links by this format), which may be truncated by this format, is detected by
pax and is repaired.
tar The old BSD tar format as found in BSD4.3. The default blocksize for this format is
10240 bytes. Pathnames stored by this format must be 100 characters or less in
length. Only regular files, hard links, soft links, and directories will be archived
(other file system types are not supported). For backwards compatibility with even
older tar formats, a -o option can be used when writing an archive to omit the storage
of directories. This option takes the form:
-o write_opt=nodir
ustar The extended tar interchange format specified in the IEEE Std 1003.2 (``POSIX.2'')
standard. The default blocksize for this format is 10240 bytes. Filenames stored by
this format must be 100 characters or less in length; the total pathname must be 255
characters or less.
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.
-Y This option is the same as the -D option, except that the inode change time is checked using
the pathname created after all the file name modifications have completed.
-Z This option is the same as the -u option, except that the modification time is checked using
the pathname created after all the file name modifications have completed.
-z Use gzip(1) to compress (decompress) the archive while writing (reading). Incompatible with
-a.
The options that operate on the names of files or archive members (-c, -i, -n, -s, -u, -v, -D, -G, -T,
-U, -Y, and -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 -c, -n, -u, -D, -G, -T, -U options. Then any -s and -i
options will modify in that order, the names of these selected files. Then the -Y and -Z options will
be applied based on the final pathname. Finally, the -v option will write the names resulting from
these modifications.
When archiving files during a write operation, or copying files during a copy operation, archive mem-bers members
bers are `selected', based only on the user specified pathnames as modified by the -n, -u, -D, -G, -T,
and -U options (the -D option only applies during a copy operation). Then any -s and -i options 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 -u or -D options are specified along with the -n option, a file is not consid-ered considered
ered selected unless it is newer than the file to which it is compared.
ENVIRONMENT
TMPDIR Path in which to store temporary files.
EXAMPLES
$ pax -w -f /dev/rst0 .
Copies the contents of the current directory to the device /dev/rst0.
$ pax -v -f filename
Gives the verbose table of contents for an archive stored in filename.
$ mkdir newdir; cd olddir; pax -rw . newdir
This sequence of commands will copy the entire olddir directory hierarchy to newdir.
$ pax -r -s ',^//*usr//*,,' -f a.pax
Reads the archive a.pax, with all files rooted in /usr into the archive extracted relative to the cur-rent current
rent directory.
$ pax -rw -i . dest_dir
Can be used to interactively select the files to copy from the current directory to dest_dir.
$ pax -r -pe -U root -G bin -f a.pax
Extract all files from the archive a.pax which are owned by root with group bin and preserve all file
permissions.
$ pax -r -w -v -Y -Z home /backup
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.
DIAGNOSTICS
pax will exit with one of the following values:
0 All files were processed successfully.
1 An error occurred.
Whenever 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 pro-cessing processing
cessing will continue. In the case where pax 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 par-tially partially
tially created the archive, which may violate the specific archive format specification.
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 when pax completes it will exit with a non-zero
exit status.
SEE ALSO
cpio(1), tar(1)
"Archiving with Pax", Dru Lavigne, ONLamp.com BSD DevCenter,
http://www.onlamp.com/pub/a/bsd/2002/08/22/FreeBSD_Basics.html
pax(1) manual page, http://heirloom.sourceforge.net/man/pax.1.html
STANDARDS
The pax utility is a superset of the IEEE Std 1003.2 (``POSIX.2'') standard. The options -B, -D, -E,
-G, -H, -L, -O, -P, -T, -U, -Y, -Z, the archive formats bcpio, sv4cpio, sv4crc, tar, and the flawed ar-
chive handling during list and read operations are extensions to the POSIX standard.
AUTHORS
Keith Muller at the University of California, San Diego.
BSD April 18, 1994 BSD
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