Provided by: pax_20240817-1_amd64 
NAME
pax — read and write file archives and copy directory hierarchies
SYNOPSIS
pax [-0cdJjnOvz] [-E limit] [-f archive] [-G group] [-s replstr] [-T range] [-U user] [pattern ...]
pax -r [-0cDdiJjknOuvYZz] [-E limit] [-f archive] [-G group] [-M flag] [-o options] [-p string]
[-s replstr] [-T range] [-U user] [pattern ...]
pax -w [-0adHiJjLOPtuvXz] [-B bytes] [-b blocksize] [-f archive] [-G group] [-M flag] [-o options]
[-s replstr] [-T range] [-U user] [-x format] [file ...]
pax -rw [-0DdHiJjkLlnOPtuvXYZ] [-G group] [-p string] [-s replstr] [-T range] [-U user] [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 pattern arguments. 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 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 -p option.
-w Write. pax writes 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.
-rw 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 glob(7). 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 pathnames
written to standard output in list mode. This option is expected to be used in concert with the
-print0 function in find(1), the -d '' option to the read built-in utility of mksh(1) or the -0
flag in xargs(1).
-a Append the given file operands 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 filesystem 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, 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.
-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.
Archive block sizes larger than 32256 bytes violate the POSIX standard and will not be portable
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
destination 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. The default limit is a
small positive number of retries.
-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 operand
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.
-J Use the xz utility to compress (decompress) the archive while writing (reading). Incompatible
with -a.
-j Use the bzip2 utility to compress (decompress) the archive while writing (reading). Incompatible
with -a.
-k Do not overwrite existing files.
-L Follow all symbolic links to perform a logical filesystem traversal.
-l (The lowercase letter “ell”.) Link files. In copy mode (-r -w), hard links are made between the
source and destination file hierarchies whenever possible.
-M flag
Configure the archive normaliser. flag is either a numeric value compatible to strtonum(3) which
is directly stored in the flags word, or one of the following values, optionally prefixed with
“no-” to turn them off:
inodes 0x0001: Serialise inodes, zero device info.
(cpio, sv4cpio, sv4crc)
links 0x0002: Store content of hard links only once.
(cpio, sv4cpio, sv4crc)
mtime 0x0004: Zero out the file modification time.
(ar, cpio, sv4cpio, sv4crc, ustar)
uidgid 0x0008: Set owner to 0:0 (root:wheel).
(ar, cpio, sv4cpio, sv4crc, ustar)
verb 0x0010: Debug this option.
debug 0x0020: Debug file header storage.
lncp 0x0040: Extract hard links by copy if link fails.
numid 0x0080: Use only numeric uid and gid values.
(ustar)
gslash 0x0100: Append a slash after directory names.
(ustar)
set 0x0003: Keep ownership and mtime intact.
dist 0x008B: Clean everything except mtime.
norm 0x008F: Clean everything.
root 0x0089: Clean owner and device information.
When creating an archive and verbosely listing output, these normalisation operations are not
reflected in the output, because they are made only after the output has been shown.
This option is only implemented for the ar, cpio, sv4cpio, sv4crc, and ustar file format writing
routines.
TODO: The pax frontend should be using the -o option for handling this feature instead.
-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
hierarchy 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 performed 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.
The following options are available for the ustar and old BSD tar formats:
write_opt=nodir
When writing archives, omit the storage of directories.
-P Do not follow symbolic links, perform a physical filesystem 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
archive. 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 privileges
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 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.
-r Read an archive file from standard input and extract the specified file operands. 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 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 archive member names according to the substitution expression replstr, using the
syntax of the ed(1) utility regular expressions. file or pattern arguments may be given to
restrict the list of archive members to those specified.
The format of these regular expressions is:
/old/new/[gp]
As in ed(1), old is a basic regular expression (see re_format(7)) and new can contain an
ampersand (‘&’), ‘\n’ (where 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 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 range
Allow files to be selected based on a file modification or inode change time falling within the
specified time range. The range has the format:
[from_date][,to_date][/[c][m]]
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.
When pax is in write or copy mode, the optional trailing field [c][m] 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 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 filesystem will be extracted if the archive member is newer than the file. During
write, a filesystem 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 information
about device IDs.
-x format
Specify the output archive format, with the default format being ustar. pax currently supports
the following formats:
ar The Unix Archiver library format. This format matches APT repositories and the BSD ar(1)
specification, not GNU binutils (which can however read them) or SYSV systems. See ar(5)
on some operating systems for more information.
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 available.
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.
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 4.3BSD. 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, symlinks and directories will be archived (other
filesystem 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 256
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 the gzip(1) utility 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 members
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 considered
selected unless it is newer than the file to which it is compared.
ENVIRONMENT
TMPDIR Path in which to store temporary files.
EXIT STATUS
The pax utility exits 0 on success, and >0 if an error occurs.
EXAMPLES
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
DIAGNOSTICS
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
processing will continue. In the case where pax cannot create a link to a file, unless -M lncp is given,
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 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
ar(1), cpio(1), deb(5), paxcpio(1), paxtar(1), tar(1)
STANDARDS
The pax utility is mostly compliant with an older version of the IEEE Std 1003.1 (“POSIX”) specification,
except for the known “BUGS” listed below, and that the pax archive format and the listopt keyword are
unsupported.
The flags -0BDEGHJjLMOPTUYZz, the archive formats ar, bcpio, sv4cpio, sv4crc and tar, the b, k, and x
additions to the -b flag and the flawed archive handling during list and read operations are extensions
to that specification.
HISTORY
A pax utility appeared in 4.4BSD.
AUTHORS
Keith Muller at the University of California, San Diego. MirBSD extensions by mirabilos <m@mirbsd.org>.
BUGS
The pattern matching does not match either POSIX or this documentation completely. See also “STANDARDS”
above.
MirBSD January 5, 2024 PAX(1)