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.
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.
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.
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.
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
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.
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.
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>.
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.
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).
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.
/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.
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.
/old/new/[gp]
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<.blm Pp
>>
new pathname<.blm Pp
>
>
ls -l listing<.blm Pp
==
link name<.blm Pp
>
>
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.
AT&T
System V.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.
AT&T
System V.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.
-o write_opt=nodir
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.
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.
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.
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.
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.
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),
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.
st_dev
field as described in
stat(2)
for more information about device ID's.
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.
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.
pax
-w
-f
/dev/rst0
.
/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
.