pax
PAX(1) BSD General Commands Manual PAX(1)
NAME
pax - read and write file archives and copy directory hierarchies
SYNOPSIS
pax [-cdnvz] [-f archive] [-s replstr] ... [-U user] ... [-G group] ...
[-T [from_date] [,to_date]] ... [pattern ...]
pax -r [-cdiknuvzDYZ] [-f archive] [-o options] ... [-p string] ...
[-s replstr] ... [-E limit] [-U user] ... [-G group] ... [-T
[from_date] [,to_date]] ... [pattern ...]
pax -w [-dituvzHLPX] [-b blocksize] [[-a] [-f archive]] [-x format]
[-s replstr] ... [-o options] ... [-U user] ... [-G group] ...
[-B bytes] [-T [from_date] [,to_date] [/[c][m]]] ... [file ...]
pax -r -w [-diklntuvDHLPXYZ] [-p string] ... [-s replstr] ... [-U user]
... [-G group] ... [-T [from_date] [,to_date] [/[c][m]]] ...
[file ...] directory
DESCRIPTION
pax will read, write, and list the members of an archive file, and will
copy directory hierarchies. pax operation is independent of the spe-
cific 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 follow-
ing 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 pos-
sible (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 sta-
tus.
The pattern operand is used to select one or more pathnames of archive
members. Archive members are selected using the pattern matching nota-
tion 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 mem-
ber, 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:
-r Read an archive file from standard input and extract the speci-
fied 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 for-
mat. When no file operands are specified, standard input is
read for a list of pathnames with one per line without any lead-
ing or trailing 〈blanks〉.
-a Append files to the end of an archive that was previously writ-
ten. 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 opera-
tions 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
64512 bytes. Archives 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 depen-
dent 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 modifi-
cation to its name. Otherwise, its name is replaced with the
contents of the line. pax will immediately exit with a non-zero
exit status if EOF is encountered when reading a response or if
/dev/tty cannot be opened for reading and writing.
-k Do not overwrite existing files.
-l (The lowercase letter “ell.”) Link files. In the copy mode (-r
-w), hard links are made between the source and destination file
hierarchies whenever possible.
-n Select the first archive member that matches each pattern
operand. No more than one archive member is matched for each
pattern. When members of type directory are matched, the file
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 charac-
teristics 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 appropri-
ate 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 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 speci-
fication 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 charac-
teristic 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 expres-
sions. The format of these regular expressions are:
/old/new/[gp]
As in ed(1), old is a basic regular expression and new can con-
tain an ampersand (‘&’), ‘\n’ (where n is a digit) back-refer-
ences, or subexpression matching. The old string may also con-
tain newline characters. Any non-null character can be used as
a delimiter (‘/’ is shown here). Multiple -s expressions can be
specified. The expressions are applied in the order they are
specified on the command line, terminating with the first suc-
cessful 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 substitu-
tion 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.
-u Ignore files that are older (having a less recent file modifica-
tion 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 mem-
ber 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.
-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 System V release 4 cpio. The default blocksize for
this format is 5120 bytes. Inode and device informa-
tion about a file (used for detecting file hard links
by this format) which may be truncated by this format
is detected by pax and is repaired.
sv4crc The System V release 4 cpio with file crc checksums.
The default blocksize for this format is 5120 bytes.
Inode and device information about a file (used for
detecting file hard links by this format) which may be
truncated by this format is detected by pax and is
repaired.
tar The old BSD tar format as found in BSD4.3. The default
blocksize for this format is 10240 bytes. Pathnames
stored by this format must be 100 characters or less in
length (including the trailing character, which means
that filenames can have a maximum length of 99 charac-
ters). 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 (including the trailing character, which means
that filenames can have a maximum length of 99 charac-
ters). Pathnames (directorynames + filenames) 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 restric-
tions. 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.
-z Use gzip(1) to compress (decompress) the archive while writing
(reading). Incompatible with -a.
-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 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.
-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 phys-
ical file system traversal.
-L Follow all symbolic links to perform a logical file system
traversal.
-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 sup-
plied, 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 modifi-
cation time is preserved). Time comparisons using both file
times is useful when pax is used to create a time based incre-
mental 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:
[yy[mm[dd[hh]]]]mm[.ss]
Where 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
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.
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 sup-
plied 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.
-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 informa-
tion about device IDs.
-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 modi-
fication time is checked using the pathname created after all
the file name modifications have completed.
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 modi-
fied 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 modifi-
cations.
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.
EXAMPLES
pax -w -f /dev/rst0 .
Copies the contents of the current directory to the device /dev/rst0.
pax -v -f filename
Gives the verbose table of contents for an archive stored in filename.
mkdir newdir cd olddir pax -rw . newdir
This sequence of commands will copy the entire olddir directory hierar-
chy to newdir.
pax -r -s ’,^//*usr//*,,’ -f a.pax
Reads the archive a.pax, with all files rooted in /usr into the archive
extracted relative to the current directory.
pax -rw -i . dest_dir
Can be used to interactively select the files to copy from the current
directory to dest_dir.
pax -r -pe -U root -G bin -f a.pax
Extract all files from the archive a.pax which are owned by root with
group bin and preserve all file permissions.
pax -r -w -v -Y -Z home /backup
Update (and list) only those files in the destination directory /backup
which are older (less recent inode change or file modification times)
than files with the same name found in the source file tree home.
DIAGNOSTICS
pax will exit with one of the following values:
0 All files were processed successfully.
1 An error occurred.
Whenever pax cannot create a file or a link when reading an archive or
cannot find a file when writing an archive, or cannot preserve the user
ID, group ID, or file mode when the -p option is specified, a diagnostic
message is written to standard error and a non-zero exit status will be
returned, but 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.
ENVIRONMENT
TMPDIR Path in which to store temporary files.
SEE ALSO
cpio(1), tar(1)
AUTHORS
Keith Muller at the University of California, San Diego.
STANDARDS
The pax utility is a superset of the IEEE Std 1003.2 (“POSIX.2”) stan-
dard. The options -B, -D, -E, -G, -H, -L, -P, -T, -U, -Y, -Z, the
archive formats bcpio, sv4cpio, sv4crc, tar, and the flawed archive han-
dling during list and read operations are extensions to the POSIX stan-
dard.
BSD April 18, 1994 BSD
