PAX(1) General Commands Manual PAX(1)
pax - read and write file archives and copy directory hierarchies
pax [-0cdjnOvz] [-E limit] [-f archive] [-G group] [-s replstr]
[-T range] [-U user] [pattern ...]
pax -r [-0cDdijknOuvYZz] [-E limit] [-f archive] [-G group] [-o options]
[-p string] [-s replstr] [-T range] [-U user] [pattern ...]
pax -w [-0adHijLOPtuvXz] [-B bytes] [-b blocksize] [-f archive]
[-G group] [-o options] [-s replstr] [-T range] [-U user] [-x format]
pax -rw [-0DdHijkLlnOPtuvXYZ] [-G group] [-p string] [-s replstr]
[-T range] [-U user] [file ...] directory
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
<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
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
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) 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
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.
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
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
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.
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.
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.
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 bzip2 to compress (decompress) the archive while writing
(reading). The bzip2 utility must be installed separately.
Incompatible with -a.
-k Do not overwrite existing files.
-L Follow all symbolic links to perform a logical file system
-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.
-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
-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.
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
When writing archives, omit the storage of directories.
-P Do not follow symbolic links, perform a physical file system
traversal. This is the default mode.
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
-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
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:
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
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
original-pathname >> new-pathname
File or archive member names that substitute to the empty string
are not selected and will be skipped.
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:
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:
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
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
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.
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
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
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, 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:
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
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
-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, -j, -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.
TMPDIR Path in which to store temporary files.
The pax utility exits 0 on success, and >0 if an error occurs.
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
$ 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
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, 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
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.
The pax utility is compliant with the IEEE Std 1003.1-2008 ("POSIX.1")
specification, except that the pax archive format and the listopt keyword
The flags [-0BDEGjOPTUYZz], the archive formats 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
A pax utility appeared in 4.4BSD.
Keith Muller at the University of California, San Diego.
OpenBSD 6.4 July 23, 2018 OpenBSD 6.4
[Unix Hosting |
[Engineering & Automation |
Software Development |