NAME
pax —
read and write file archives and
copy directory hierarchies
SYNOPSIS
pax |
[-0cdjnOVvz]
[-E limit]
[-f
archive]
[-N dbdir]
[-s
replstr] ...
[-U user]
... [-G
group] ...
[-T
[from_date][,to_date]]
... [pattern
...] |
pax |
-r
[-AcDdijknOuVvYZz]
[-E limit]
[-f
archive]
[-N dbdir]
[-o
options] ...
[-p
string] ...
[-s
replstr] ...
[-U user]
... [-G
group] ...
[-T
[from_date][,to_date]]
... [pattern
...] |
pax |
-w
[-AdHijLMOPtuVvXz]
[-b
blocksize]
[[-a]
[-f
archive]]
[-x
format]
[-B bytes]
[-N dbdir]
[-o
options] ...
[-s
replstr] ...
[-U user]
... [-G
group] ...
[-T
[from_date][,to_date][/[c][m]]]
... [file
...] |
pax |
-r -w
[-ADdHijkLlMnOPtuVvXYZz]
[-N dbdir]
[-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. If the archive file is of the form:
[[user@]host:]file then the archive will be processed
using
rmt(8).
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 pathnames matching the specified
patterns. 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.
-
-
- -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).
OPERANDS
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.
OPTIONS
The following options are supported:
-
-
- -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.
-
-
- -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⟩.
-
-
- -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
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 32256 bytes. 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
- 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.
-
-
- -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.
-
-
- -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(1)
for compression when reading or writing archive files.
-
-
- -k
- Do not overwrite existing files.
-
-
- -l
- Link files. (The letter ell). 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 hierarchy rooted at that directory is also
matched (unless -d is also specified).
-
-
- -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
-
-
- -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 meaning 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.
-
-
- -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 are:
/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 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
- 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, if the user has the appropriate
permissions required by
utime(3).
-
-
- -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⟩
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.
A final summary of archive operations is printed after they have been
completed.
-
-
- -x
format
- Specify the output archive format, with the default format
being ustar. pax currently
supports the following formats:
-
-
- 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.
-
-
- 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.
-
-
- sv4cpio
- The AT&T System V
Release 4 UNIX 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 AT&T System V
Release 4 UNIX 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 types are
not supported). For backward 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.
Pathnames stored by this format must be 250 characters or less in
length.
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.
-
-
- --gnu
- Recognize GNU tar extensions.
-
-
- --timestamp
timestamp
- Store all modification times in the archive with the
timestamp given instead of the actual modification
time of the individual archive member so that repeatable builds are
possible. The timestamp can be a
pathname, where the timestamps are derived from that
file, a parseable date for
parsedate(3) (this option
is not yet available in the tools build), or an integer value interpreted
as the number of seconds from the Epoch.
-
-
- --xz
- Use xz(1)
compression, when reading or writing archive files.
-
-
- -z
- Use gzip(1)
compression, when reading or writing archive files.
-
-
- -A
- Do not strip leading `/'s from file names.
-
-
- -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.
-
-
- -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.
-
-
- -E
limit
- Limit the number of consecutive read faults while trying to
read a flawed archives 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.
-
-
- -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.
-
-
- -L
- Follow all symbolic links to perform a logical file system
traversal.
-
-
- -M
- During a write or copy
operation, treat the list of files on
standard
input
as an mtree(8)
‘specfile’ specification, and write or copy only those items
in the specfile.
If the file exists in the underlying file system, its permissions and
modification time will be used unless specifically overridden by the
specfile. An error will be raised if the type of entry in the specfile
conflicts with that of an existing file. A directory entry that is marked
‘optional’ will not be copied (even though
its contents will be).
Otherwise, the entry will be ‘faked-up’, and it is necessary to
specify at least the following parameters in the specfile:
type, mode, gname or
gid, and uname or
uid, device (in the case of block or
character devices), and link (in the case of symbolic
links). If time isn't provided, the current time will be
used. A ‘faked-up’ entry that is marked
‘optional’ will not be copied.
-
-
- -N
dbdir
- Except for lookups for the -G and
-U options, use the user database text file
master.passwd and group database text file
group from dbdir, rather than
using the results from the system's
getpwnam(3) and
getgrnam(3) (and related)
library calls.
-
-
- -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.
-
-
- -P
- Do not follow symbolic links, perform a physical file
system traversal. This is the default mode.
-
-
- -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 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 seven 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), the second
mm is the minute (from 00 to 59), and
ss is the seconds (from 00 to 61). Only the minute field
mm is required; the others will default to the current
system values. The ss field may be added independently
of the other fields. If the century is not specified, it defaults to 1900
for years between 69 and 99, or 2000 for years between 0 and 68. 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.
-
-
- -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.
-
-
- -V
- A final summary of archive operations is printed after they
have been completed. Some potentially long-running tape operations are
noted.
-
-
- -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 ID's.
-
-
- -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.
-
-
- -0
- Use the nul character instead of \n as the file separator
when reading files from standard input.
-
-
- --force-local
- Do not interpret filenames that contain a `:' as remote
files.
-
-
- --insecure
- Normally pax ignores filenames that
contain “..” as a path component. With this option, files that
contain “..” can be processed.
-
-
- --use-compress-program
- Use the named program as the program to decompress the
input or compress the output.
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.
EXIT STATUS
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 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 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.
EXAMPLES
The command:
pax -w -f /dev/rst0 .
copies the contents of the current directory to the device
/dev/rst0.
The command:
pax -v -f filename
gives the verbose table of contents for an archive stored in
filename.
The following commands:
mkdir newdir
cd olddir
pax -rw -pp . ../newdir
will copy the entire
olddir directory hierarchy to
newdir, preserving permissions and access times.
When running as root, one may also wish to preserve file ownership when copying
directory trees. This can be done with the following commands:
cd olddir
pax -rw -pe . ../newdir
which will copy the contents of
olddir into
../newdir, preserving ownership, permissions and access
times.
The command:
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 current directory.
The command:
pax -rw -i . dest_dir
can be used to interactively select the files to copy from the current directory
to
dest_dir.
The command:
pax -r -pe -U root -G bin -f a.pax
will extract all files from the archive
a.pax which are owned
by
root with group
bin and will preserve
all file permissions.
The command:
pax -r -w -v -Y -Z home /backup
will 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.
SEE ALSO
cpio(1),
tar(1),
symlink(7),
mtree(8)
STANDARDS
The
pax utility is a superset of the
IEEE Std
1003.2 (“POSIX.2”) standard. The options
-B,
-D,
-E,
-G,
-H,
-L,
-M,
-O,
-P,
-T,
-U,
-Y,
-Z,
-z, the archive formats
bcpio,
sv4cpio,
sv4crc,
tar, and the flawed
archive handling during
list and
read operations are extensions to the POSIX standard.
HISTORY
A
pax utility appeared in
4.4BSD.
AUTHORS
Keith Muller at the University of California, San Diego.
Luke Mewburn implemented
-M.