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(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
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 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, 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. 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 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 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.
-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 old BSD
tar format:
nodir
-
write_opt=nodir
- 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.
-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 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 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:
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 the
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 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 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, 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 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 with one of the
following values:
- 0
- All files were processed successfully.
- 1
- An error occurred.
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 compliant with the IEEE
Std 1003.1-2008 (“POSIX”) specification.
The flags
-0BDEGHJjLMOPTUYZz
, the archive
formats
ar,
bcpio,
sv4cpio,
sv4crc,
tar, and the flawed archive handling during
list and
read
operations are extensions to that specification.
AUTHORS¶
Keith Muller at the University of California, San Diego.
MirOS extensions by
Thorsten Glaser
⟨tg@mirbsd.org⟩.
BUGS¶
The
pax file format is not yet supported.