PAX(1)PAX(1)NAMEpax - portable archive interchange
SYNOPSISpax [-cdnv] [-H | -L] [-f archive] [-o options]...
[-s replstr]... [pattern]...
pax-r [-cdiknuv@/] [-H | -L] [-f archive] [-o options]...
[-p string]... [-s replstr]... [pattern]...
pax-w [-dituvX@/] [-H | -L] [-b blocksize] [-a]
[-f archive] [-o options]... [-s replstr]...
[-x format] [file]...
pax-r -w [-diklntuvX@/] [-H | -L] [-o options]...
[-p string]... [-s replstr]... [file]... directory
DESCRIPTIONpax reads, writes, and writes lists of the members of archive files and
copies directory hierarchies. A variety of archive formats are sup‐
ported. See the -x format option.
Modes of Operations
The action to be taken depends on the presence of the -r and -w
options. The four combinations of -r and -w are referred to as the four
modes of operation: list, read, write, and copy modes, corresponding
respectively to the four forms shown in the SYNOPSIS.
list
In list mode, that is, when neither -r nor -w are specified,
pax writes the names of the members of the archive file read
from the standard input, with path names matching the speci‐
fied patterns, to standard output. If a named file has
extended attributes, the extended attributes are also listed.
If a named file is of type directory, the file hierarchy
rooted at that file is listed as well.
read
In read mode, that is, when -r is specified, but -w is not,
pax extracts the members of the archive file read from the
standard input, with path names matching the specified pat‐
terns. If an extracted file is of type directory, the file
hierarchy rooted at that file is extracted as well. The
extracted files are created performing path name resolution
with the directory in which pax was invoked as the current
working directory.
If an attempt is made to extract a directory when the direc‐
tory already exists, this is not considered an error. If an
attempt is made to extract a FIFO when the FIFO already
exists, this is not considered an error.
The ownership, access and modification times, and file mode of
the restored files are discussed under the -p option.
write
In write mode, that is, when -w is specified, but -r is not,
pax writes the contents of the file operands to the standard
output in an archive format. If no file operands are speci‐
fied, a list of files to copy, one per line, are read from the
standard input. A file of type directory includes all of the
files in the file hierarchy rooted at the file.
copy
In copy mode, that is, when both -r and -w are specified, pax
copies the file operands to the destination directory.
If no file operands are specified, a list of files to copy,
one per line, are read from the standard input. A file of type
directory includes all of the files in the file hierarchy
rooted at the file.
The effect of the copy is as if the copied files were written
to an archive file and then subsequently extracted, except
that there can be hard links between the original and the
copied files. If the destination directory is a subdirectory
of one of the files to be copied, the results are unspecified.
It is an error if directory does not exist, is not writable by
the user, or is not a directory.
In read or copy modes, if intermediate directories are necessary to
extract an archive member, pax performs actions equivalent to the
mkdir(2) function, called with the following arguments:
o The intermediate directory used as the path argument.
o The octal value of 777 or rwx (read, write, and execute per‐
missions) as the mode argument (see chmod(1)).
If any specified pattern or file operands are not matched by at least
one file or archive member, pax writes a diagnostic message to standard
error for each one that did not match and exits with a non-zero exit
status.
The supported archive formats are automatically detected on input. The
default output archive format is tar(1).
A single archive can span multiple files. pax determines what file to
read or write as the next file.
If the selected archive format supports the specification of linked
files, it is an error if these files cannot be linked when the archive
is extracted, except if the files to be linked are symbolic links and
the system is not capable of making hard links to symbolic links. In
that case, separate copies of the symbolic link are created instead.
Any of the various names in the archive that represent a file can be
used to select the file for extraction. For archive formats that do
not store file contents with each name that causes a hard link, if the
file that contains the data is not extracted during this pax session,
either the data is restored from the original file, or a diagnostic
message is displayed with the name of a file that can be used to
extract the data. In traversing directories, pax detects infinite
loops, that is, entering a previously visited directory that is an
ancestor of the last file visited. When it detects an infinite loop,
pax writes a diagnostic message to standard error and terminates.
OPTIONS
The following options are supported:
-a
Appends files to the end of the archive. This option
does not work for some archive devices, such as
1/4-inch streaming tapes and 8mm tapes.
-b blocksize
Blocks the output at a positive decimal integer number
of bytes per write to the archive file. Devices and ar‐
chive formats can impose restrictions on blocking.
Blocking is automatically determined on input. Portable
applications must not specify a blocksize value larger
than 32256. Default blocking when creating archives
depends on the archive format. See the -x option below.
-c
Matches all file or archive members except those speci‐
fied by the pattern or file operands.
-d
Causes files of type directory being copied or archived
or archive members of type directory being extracted or
listed to match only the file or archive member itself
and not the file hierarchy rooted at the file.
-f archive
Specifies the path name of the input or output archive,
overriding the default standard input (in list or read
modes) or standard output (write mode).
-H
If a symbolic link referencing a file of type directory
is specified on the command line, pax archives the file
hierarchy rooted in the file referenced by the link,
using the name of the link as the root of the file
hierarchy. Otherwise, if a symbolic link referencing a
file of any other file type which pax can normally ar‐
chive is specified on the command line, then pax ar‐
chives the file referenced by the link, using the name
of the link. The default behavior is to archive the
symbolic link itself.
-i
Interactively renames files or archive members. For
each archive member matching a pattern operand or file
matching a file operand, a prompt is written to the
file /dev/tty. The prompt contains the name of the file
or archive member. A line is then read 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 modifica‐
tion to its name. Otherwise, its name is replaced with
the contents of the line. pax immediately exits with a
non-zero exit status if end-of-file is encountered when
reading a response or if /dev/tty cannot be opened for
reading and writing.
The results of extracting a hard link to a file that
has been renamed during extraction are unspecified.
-k
Prevents the overwriting of existing files.
-l
Links files. In copy mode, hard links are made between
the source and destination file hierarchies whenever
possible. If specified in conjunction with -H or -L,
when a symbolic link is encountered, the hard link cre‐
ated in the destination file hierarchy is to the file
referenced by the symbolic link. If specified when nei‐
ther -H nor -L is specified, when a symbolic link is
encountered, the implementation creates a hard link to
the symbolic link in the source file hierarchy or
copies the symbolic link to the destination.
-L
If a symbolic link referencing a file of type directory
is specified on the command line or encountered during
the traversal of a file hierarchy, pax archives the
file hierarchy rooted in the file referenced by the
link, using the name of the link as the root of the
file hierarchy. Otherwise, if a symbolic link referenc‐
ing a file of any other file type which pax can nor‐
mally archive is specified on the command line or
encountered during the traversal of a file hierarchy,
pax archives the file referenced by the link, using the
name of the link. The default behavior is to archive
the symbolic link itself.
-n
Selects the first archive member that matches each pat‐
tern operand. No more than one archive member is
matched for each pattern, although members of type
directory still match the file hierarchy rooted at that
file.
-o options
Provides information to the implementation to modify
the algorithm for extracting or writing files. The
value of options consists of one or more comma-sepa‐
rated keywords of the form:
keyword[[:]=value][,keyword[[:]=value], ...]
Some keywords apply only to certain file formats, as
indicated with each description. Use of keywords that
are inapplicable to the file format being processed
produces undefined results.
Keywords in the options argument must be a string that
would be a valid portable filename.
Keywords are not expected to be filenames, merely to
follow the same character composition rules as portable
filenames.
Keywords can be preceded with white space. The value
field consists of zero or more characters. Within
value, the application precedes any literal comma with
a backslash, which is ignored, but preserves the comma
as part of value. A comma as the final character, or a
comma followed solely by white space as the final char‐
acters, in options is ignored. Multiple -o options can
be specified. If keywords given to these multiple -o
options conflict, the keywords and values appearing
later in command line sequence take precedence and the
earlier ones are silently ignored. The following key‐
word values of options are supported for the file for‐
mats as indicated:
delete=pattern
This keyword is applicable only to the -xpax for‐
mat. When used in write or copy mode, pax omits
from extended header records that it produces any
keywords matching the string pattern. When used in
read or list mode, pax ignores any keywords match‐
ing the string pattern in the extended header
records. In both cases, matching is performed using
the pattern matching notation. For example:
-o delete=security.*
would suppress security-related information.
When multiple -o delete=pattern options are speci‐
fied, the patterns are additive. All keywords
matching the specified string patterns are omitted
from extended header records that pax produces.
exthdr.name=string
This keyword is applicable only to the -xpax for‐
mat. This keyword allows user control over the name
that is written into the ustar header blocks for
the extended header. The name is the contents of
string, after the following character substitutions
have been made:
%d
The directory name of the file, equivalent to
the result of the dirname utility on the
translated path name.
%f
The filename of the file, equivalent to the
result of the basename utility on the trans‐
lated path name.
%p
The process ID of the pax process.
%%
A '%' character.
Any other '%' characters in string produce unde‐
fined results.
If no -o exthdr.name=string is specified, pax uses
the following default value:
%d/PaxHeaders.%p/%f
globexthdr.name=string
This keyword is applicable only to the -xpax for‐
mat. When used in write or copy mode with the
appropriate options, pax creates global extended
header records with ustar header blocks that are
treated as regular files by previous versions of
pax. This keyword allows user control over the name
that is written into the ustar header blocks for
global extended header records. The name is the
contents of string, after the following character
substitutions have been made:
%n
An integer that represents the sequence num‐
ber of the global extended header record in
the archive, starting at 1.
%p
The process ID of the pax process.
%%
A '%' character.
Any other '%' characters in string produce unde‐
fined results.
If no -o globexthdr.name=string is specified, pax
uses the following default value:
$TMPDIR/GlobalHead.%p.%n
where $TMPDIR represents the value of the TMPDIR
environment variable. If TMPDIR is not set, pax
uses /tmp.
invalid=action
This keyword is applicable only to the -xpax for‐
mat. This keyword allows user control over the
action pax takes upon encountering values in an
extended header record that, in read or copy mode,
are invalid in the destination hierarchy or, in
list mode , cannot be written in the codeset and
current locale of the implementation. The following
are invalid values that are recognized by pax:
o In read or copy mode, a filename or link
name that contains character encodings
invalid in the destination hierarchy.
For example, the name can contain embed‐
ded NULs.
o In read or copy mode, a filename or link
name that is longer than the maximum
allowed in the destination hierarchy,
for either a path name component or the
entire path name.
o In list mode, any character string value
(filename, link name, user name, and so
on) that cannot be written in the code‐
set and current locale of the implemen‐
tation.
The following mutually-exclusive values of the
action argument are supported:
bypass
In read or copy mode, pax bypasses the
file, causing no change to the destina‐
tion hierarchy. In list mode, pax writes
all requested valid values for the file,
but its method for writing invalid values
is unspecified.
rename
In read or copy mode, pax acts as if the
-i option were in effect for each file
with invalid filename or link name val‐
ues, allowing the user to provide a
replacement name interactively. In list
mode, pax behaves identically to the
bypass action.
UTF-8
pax uses the actual UTF-8 encoding for
the name when it is used in read, copy,
or list mode and a filename, link name,
owner name, or any other field in an
extended header record cannot be trans‐
lated from the pax UTF-8 codeset format
to the codeset and current locale of the
implementation.
write
In read or copy mode, pax writes the
file, translating the name, regardless of
whether this can overwrite an existing
file with a valid name. In list mode, pax
behaves identically to the bypass action.
If no -o invalid= option is specified, pax acts as
if -o invalid=bypass were specified. Any overwrit‐
ing of existing files that can be allowed by the -o
invalid= actions are subject to permission (-p) and
modification time (-u) restrictions, and are sup‐
pressed if the -k option is also specified.
linkdata
This keyword is applicable only to the -xpax for‐
mat. In write mode, pax writes the contents of a
file to the archive even when that file is merely a
hard link to a file whose contents have already
been written to the archive.
listopt=format
This keyword specifies the output format of the ta‐
ble of contents produced when the -v option is
specified in list mode. (See List Mode Format Spec‐
ifications below.) To avoid ambiguity, the
listopt=format is the only or final keyword=value
pair in an -o option-argument. All characters in
the remainder of the option-argument are considered
to be part of the format string. When multiple -o
listopt=format options are specified, the format
strings are considered to be a single, concatenated
string, evaluated in command line order.
times
This keyword is applicable only to the -xpax and
-x xustar formats. When used in write or copy mode,
pax includes atime and mtime extended header
records for each file.
In addition to these keywords, if the -xpax format is
specified, any of the keywords and values, including
implementation extensions, can be used in -o option-
arguments, in either of two modes:
keyword=value
When used in write or copy mode,
these keyword/value pairs are
included at the beginning of the ar‐
chive as typeflag g global extended
header records. When used in read or
list mode, these keyword/value pairs
act as if they had been at the begin‐
ning of the archive as typeflag g
global extended header records.
keyword:=value
When used in write or copy mode,
these keyword/value pairs are
included as records at the beginning
of a typeflag x extended header for
each file. This is equivalent to the
equal-sign form except that it cre‐
ates no typeflag g global extended
header records. When used in read or
list mode, these keyword/value pairs
act as if they were included as
records at the end of each extended
header. Thus, they override any
global or file-specific extended
header record keywords of the same
names. For example, in the command:
pax-r -o "
gname:=mygroup,
" <archive
the group name is forced to a new
value for all files read from the ar‐
chive.
-p string
Specifies one or more file characteristic options
(privileges). The string option-argument must be 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 is as follows:
a
Does not preserve file access times.
e
Preserves the user ID, group ID, file mode bits,
access time, and modification time.
m
Does not preserve file modification times.
o
Preserves the user ID and group ID.
p
Preserves the file mode bits.
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 is deter‐
mined as part of the normal file creation action. The
access and modification times of the file is preserved
unless otherwise specified with the -p option or not
stored in the archive. All attributes that are not pre‐
served are determined as part of the normal file cre‐
ation action.
If neither the e nor the o specification character is
specified, or the user ID and group ID are not pre‐
served for any reason, pax does not set the setuid and
setgid bits of the file mode.
If the preservation of any of these items fails for any
reason, pax writes a diagnostic message to standard
error. Failure to preserve these items affects the
final exit status, but does not cause the extracted
file to be deleted.
If file-characteristic letters in any of the string
option-arguments are duplicated or conflict with each
other, the ones given last take precedence. For exam‐
ple, if -p eme is specified, file modification times
are preserved.
-r
Reads an archive file from standard input.
-s replstr
Modifies file or archive member names named by pattern
or file operands according to the substitution expres‐
sion replstr, which is based on the ed(1) s (substitu‐
tion) utility, using the regular expression syntax of
regex(5). The concepts of ``address'' and ``line'' are
meaningless in the context of the pax command, and must
not be supplied. The format is:
-s /old/new/ [gp]
where, as in ed, old is a basic regular expression and
new can contain an ampersand (&), a \n backreference,
where n is a digit, or subexpression matching. The old
string is also permitted to contain newlines.
Any non-null character can be used as a delimiter (/
shown here). Multiple -s expressions can be specified.
The expressions are applied in the order specified,
terminating with the first successful substitution. The
optional trailing g is as defined in the ed command.
The optional trailing p causes successful substitutions
to be written to standard error. File or archive member
names that substitute to the empty string are ignored
when reading and writing archives.
-t
When reading files from the file system, and if the
user has the permissions required by utime() to do so,
sets the access time of each file read to the access
time that it had before being read by pax.
-u
Ignores files that are older (having a less recent file
modification time) than a pre-existing file or archive
member with the same name.
read mode
An archive member with the same name as a
file in the file system is extracted if
the archive member is newer than the
file.
write mode
An archive file member with the same name
as a file in the file system is super‐
seded if the file is newer than the ar‐
chive member. If option -a is also speci‐
fied, this is accomplished by appending
to the archive. Otherwise, it is unspeci‐
fied whether this is accomplished by
actual replacement in the archive or by
appending to the archive.
copy mode
The file in the destination hierarchy is
replaced by the file in the source hier‐
archy or by a link to the file in the
source hierarchy if the file in the
source hierarchy is newer.
-v
In list mode, produces a verbose table of contents (see
Standard Output). Otherwise, writes archive member path
names and extended attributes to standard error (see
Standard Error).
-w
Writes files to the standard output in the specified
archive format.
-x format
Specifies the output archive format. The pax utility
recognizes the following formats:
cpio
The extended cpio(1) interchange format. See
IEEE Std 1003.1-2001. The default blocksize
for this format for character special archive
files is 5120. Implementations support all
blocksize values less than or equal to 32256
that are multiples of 512.
This archive format allows files with UIDs
and GIDs up to 262143 to be stored in the ar‐
chive. Files with UIDs and GIDs greater than
this value are archived with the UID and GID
of 60001.
pax
The pax interchange format. See IEEE Std
1003.1-2001. The default blocksize for this
format for character special archive files is
5120. Implementations support all blocksize
values less than or equal to 32256 that are
multiples of 512.
Similar to ustar. Also allows archiving and
extracting files whose size is greater than
8GB; whose UID, GID, devmajor, or devminor
values are greater than 2097151; whose path
(including filename) is greater than 255
characters; or whose linkname is greater than
100 characters.
ustar
The extended tar(1) interchange format. See
the IEEE 1003.1(1990) specifications. The
default blocksize for this format for charac‐
ter special archive files is 10240. Implemen‐
tations support all blocksize values less
than or equal to 32256 that are multiples of
512.
This archive format allows files with UIDs
and GIDs up to 2097151 to be stored in the
archive. Files with UIDs and GIDs greater
than this value are archived with the UID and
GID of 60001.
xustar
Similar to ustar. Also allows archiving and
extracting files whose size is greater than
8GB; whose UID, GID, devmajor, or devminor
values are greater than 2097151; whose path
(including filename) is greater than 255
characters; or whose linkname is greater than
100 characters. This option should not be
used if the archive is to be extracted by an
archiver that cannot handle the larger val‐
ues.
Any attempt to append to an archive file in a format
different from the existing archive format causes pax
to exit immediately with a non-zero exit status.
In copy mode, if no -x format is specified, pax behaves
as if -xpax were specified.
-X
When traversing the file hierarchy specified by a path
name, pax does not descend into directories that have a
different device ID (st_dev, see stat(2)).
-@
Includes extended attributes in the archive. pax does
not place extended attributes in the archive by
default.
When traversing the file hierarchy specified by a path
name, pax descends into the attribute directory for any
file with extended attributes. Extended attributes go
into the archive as special files.
When this flag is used during file extraction, any
extended attributes associated with a file being
extracted are also extracted. Extended attribute files
can only be extracted from an archive as part of a nor‐
mal file extract. Attempts to explicitly extract
attribute records are ignored.
-/
Includes extended system attributes in the archive. pax
does not place extended system attributes in the ar‐
chive by default.
When traversing the file hierarchy specified by a path
name, pax descends into the attribute directory for any
file with extended attributes. Extended attributes go
into the archive as special files. When this flag is
used during file extraction, any extended attributes
associated with a file being extracted are also
extracted. Extended attribute files can only be
extracted from an archive as part of a normal file
extract. Attempts to explicitly extract attribute
records are ignored.
Specifying more than one of the mutually-exclusive options -H and -L is
not considered an error. The last option specified determines the
behavior of the utility.
The options that operate on the names of files or archive members (-c,
-i, -n, -s, -u and -v) interact as follows.
In read mode, the archive members are selected based on the user-speci‐
fied pattern operands as modified by the -c, -n and -u options. Then,
any -s and -i options modify, in that order, the names of the selected
files. The -v option writes names resulting from these modifications.
In write mode, the files are selected based on the user-specified path
names as modified by the -n and -u options. Then, any -s and -i options
modify, in that order, the names of these selected files. The -v option
writes names resulting from these modifications.
If both the -u and -n options are specified, pax does not consider a
file selected unless it is newer than the file to which it is compared.
List Mode Format Specifications
In list mode with the -o listopt=format option, the format argument is
applied for each selected file. pax appends a NEWLINE to the listopt
output for each selected file. The format argument is used as the for‐
mat string with the following exceptions. (See printf(1) for the first
five exceptions.)
1. A SPACE character in the format string, in any context other
than a flag of a conversion specification, is treated as an
ordinary character that is copied to the output.
2. A ' ' character in the format string is treated as a ' '
character, not as a SPACE.
3. In addition to the escape sequences described in the for‐
mats(5) manual page, (\\, \a, \b, \f, \n, \r, \t, \v), \ddd,
where ddd is a one-, two-, or three-digit octal number, is
written as a byte with the numeric value specified by the
octal number.
4. Output from the d or u conversion specifiers is not preceded
or followed with BLANKs not specified by the format operand.
5. Output from the o conversion specifier is not preceded with
zeros that are not specified by the format operand.
6. The sequence (keyword) can occur before a format conversion
specifier. The conversion argument is defined by the value
of keyword. The following keywords are supported (see IEEE
Std 1003.1-2001):
o Any of the Field Name entries in ustar Header Block and
Octet-Oriented cpio Archive Entry. The implementation
supports the cpio keywords without the leading c_ in
addition to the form required by Values for cpio c_ mode
Field.
o Any keyword defined for the extended header in pax
Extended Header.
o Any keyword provided as an implementation-defined exten‐
sion within the extended header defined in pax Extended
Header.
For example, the sequence "%(charset)s" is the string value of the
name of the character set in the extended header.
The result of the keyword conversion argument is the value from the
applicable header field or extended header, without any trailing
NULs.
All keyword values used as conversion arguments are translated from
the UTF -8 encoding to the character set appropriate for the local
file system, user database, and so on, as applicable.
7. An additional conversion specifier character, T, is used to
specify time formats. The T conversion specifier character
can be preceded by the sequence (keyword=subformat), where
subformat is a date format as defined by date operands. The
default keyword is mtime and the default subformat is:
%b %e %H:%M %Y
8. An additional conversion specifier character, M, is used to
specify the file mode string as defined in ls Standard Out‐
put. If (keyword) is omitted, the mode keyword is used. For
example, %.1M writes the single character corresponding to
the entry type field of the ls -l command.
9. An additional conversion specifier character, D, is used to
specify the device for block or special files, if applica‐
ble, in an implementation-defined format. If not applicable,
and (keyword) is specified, then this conversion is equiva‐
lent to %(keyword)u. If not applicable, and (keyword) is
omitted, then this conversion is equivalent to SPACE.
10. An additional conversion specifier character, F, is used to
specify a path name. The F conversion character can be pre‐
ceded by a sequence of comma-separated keywords:
(keyword[,keyword] ... )
The values for all the keywords that are non-null are con‐
catenated, each separated by a '/'. The default is (path) if
the keyword path is defined. Otherwise, the default is (pre‐
fix,name).
11. An additional conversion specifier character, L, is used to
specify a symbolic link expansion. If the current file is a
symbolic link, then %L expands to:
"%s -> %s", value of keyword, contents of link
Otherwise, the %L conversion specification is the equivalent
of %F.
OPERANDS
The following operands are supported:
directory
The destination directory path name for copy mode.
file
A path name of a file to be copied or archived.
pattern
A pattern matching one or more path names of archive mem‐
bers. A pattern must conform to the pattern matching nota‐
tion found on the fnmatch(5) manual page. The default, if
no pattern is specified, is to select all members in the
archive.
OUTPUT
Output formats are discussed below:
Standard Output
In write mode, if -f is not specified, the standard output is the ar‐
chive formatted according to one of the formats described below. See -x
format for a list of supported formats.
In list mode, when the -o listopt=format option has been specified, the
selected archive members are written to standard output using the for‐
mat described above under List Mode Format Specifications. In list
mode without the -o listopt=format option, the table of contents of the
selected archive members are written to standard output using the fol‐
lowing format:
"%s\n", pathname
If the -v option is specified in list mode, the table of contents of
the selected archive members are written to standard output using the
following formats:
o For path names representing hard links to previous members
of the archive:
"%s == %s\n", <ls -l listing, linkname
o For all other path names:
"%s\n", <ls -l listing>
where <ls -l listing> is the format specified by the ls com‐
mand with the -l option. When writing path names in this
format, it is unspecified what is written for fields for
which the underlying archive format does not have the cor‐
rect information, although the correct number of blank-char‐
acter-separated fields is written.
In list mode, standard output is not buffered more than a line at a
time.
Standard Error
If -v is specified in read, write or copy modes, pax writes the path
names it processes to the standard error output using the following
format:
"%s\n", pathname
These path names are written as soon as processing is begun on the file
or archive member, and are flushed to standard error. The trailing NEW‐
LINE character, which is not buffered, is written when the file has
been read or written.
If the -s option is specified, and the replacement string has a trail‐
ing p, substitutions are written to standard error in the following
format:
"%s >> %s\n", <original pathname>, <new pathname>
In all operating modes of pax, optional messages of unspecified format
concerning the input archive format and volume number, the number of
files, blocks, volumes, and media parts as well as other diagnostic
messages can be written to standard error.
In all formats, for both standard output and standard error, it is
unspecified how non-printable characters in path names or link names
are written.
When pax is in read mode or list mode, using the -xpax archive format,
and a file name, link name, owner name, or any other field in an
extended header record cannot be translated from the pax UTF-8 codeset
format to the codeset and current locale of the implementation, pax
writes a diagnostic message to standard error, processes the file as
described for the -o invalid=option, and then processes the next file
in the archive.
Output Files
In read mode, the extracted output files are of the archived file type.
In copy mode, the copied output files are the type of the file being
copied . In either mode, existing files in the destination hierarchy
are overwritten only when all permission (-p), modification time (-u),
and invalid-value (-o invalid=) tests allow it. In write mode, the out‐
put file named by the -f option-argument is a file formatted according
to one of the specifications in IEEE Std 1003.1-2001.
ERRORS
If pax cannot create a file or a link when reading an archive, or can‐
not 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 diagnos‐
tic message is written to standard error and a non-zero exit status is
returned, but processing continues. In the case where pax cannot create
a link to a file, pax does not, by default, 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 can have only partially extracted the file
or, if the -n option was not specified, can have extracted a file of
the same name as that specified by the user, but which is not the file
the user wanted. Additionally, the file modes of extracted directories
can have additional bits from the read, write, execute mask set as well
as incorrect modification and access times.
USAGE
The -p (privileges) option was invented to reconcile differences
between historical tar(1) and cpio(1) implementations. In particular,
the two utilities use -m in diametrically opposed ways. The -p option
also provides a consistent means of extending the ways in which future
file attributes can be addressed, such as for enhanced security systems
or high-performance files. Although it can seem complex, there are
really two modes that are most commonly used:
-p e
Preserve everything. This would be used by the historical supe‐
ruser, someone with all the appropriate privileges, to preserve
all aspects of the files as they are recorded in the archive.
The e flag is the sum of o and p, and other implementation-
dependent attributes.
-p p
Preserve the file mode bits. This would be used by the user
with regular privileges who wished to preserve aspects of the
file other than the ownership. The file times are preserved by
default, but two other flags are offered to disable these and
use the time of extraction.
The one path name per line format of standard input precludes path
names containing newlines. Although such path names violate the porta‐
ble filename guidelines, they can exist and their presence can inhibit
usage of pax within shell scripts. This problem is inherited from his‐
torical archive programs. The problem can be avoided by listing file
name arguments on the command line instead of on standard input.
It is almost certain that appropriate privileges are required for pax
to accomplish parts of this. Specifically, creating files of type block
special or character special, restoring file access times unless the
files are owned by the user (the -t option), or preserving file owner,
group, and mode (the -p option) all probably require appropriate privi‐
leges.
In read mode, implementations are permitted to overwrite files when the
archive has multiple members with the same name. This can fail if per‐
missions on the first version of the file do not permit it to be over‐
written.
When using the -x xustar and -x -pax archive formats, if the underlying
file system reports that the file being archived contains holes, the
Solaris pax utility records the presence of holes in an extended header
record when the file is archived. If this extended header record is
associated with a file in the archive, those holes are recreated when‐
ever that file is extracted from the archive. See the SEEK_DATA and
SEEK_HOLE whence values in lseek(2). In all other cases, any NUL (\0)
characters found in the archive is written to the file when it is
extracted.
See largefile(5) for the description of the behavior of pax when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).
Standard Input
In write mode, the standard input is used only if no file operands are
specified. It is a text file containing a list of path names, one per
line, without leading or trailing blanks. In list and read modes, if -f
is not specified, the standard input is an archive file. Otherwise, the
standard input is not used.
Input Files
The input file named by the archive option-argument, or standard input
when the archive is read from there, is a file formatted according to
one of the formats described below. See Extended Description. The file
/dev/tty is used to write prompts and read responses.
EXAMPLES
Example 1 Copying the Contents of the Current Directory
The following command:
example% pax-w -f /dev/rmt/1m .
copies the contents of the current directory to tape drive 1, medium
density. This assumes historical System V device naming procedures.
The historical BSD device name would be /dev/rmt9.
Example 2 Copying the Directory Hierarchy
The following commands:
example% mkdir newdir
example% pax-rw olddir newdir
copy the olddir directory hierarchy to newdir.
Example 3 Reading an Archive Extracted Relative to the Current Direc‐
tory
The following command:
example% pax-r -s ',^//*usr//*,,' -f a.pax
reads the archive a.pax, with all files rooted in /usr in the archive
extracted relative to the current directory.
Example 4 Overriding the Default Output Description
Using the option:
-o listopt="%M %(atime)T %(size)D %(name)s"
overrides the default output description in Standard Output and instead
writes:
-rw-rw- - - Jan 12 15:53 2003 1492 /usr/foo/bar
Using the options:
-o listopt='%L\t%(size)D\n%.7' \
-o listopt='(name)s\n%(atime)T\n%T'
overrides the default output description in standard output and instead
writes:
usr/foo/bar -> /tmp 1492
/usr/foo
Jan 12 15:53 1991
Jan 31 15:53 2003
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables
that affect the execution of pax: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES,
LC_TIME, and NLSPATH.
LC_COLLATE
Determine the locale for the behaviour of ranges, equiva‐
lence classes, and multi-character collating elements
used in the pattern matching expressions for the pattern
operand, the basic regular expression for the -s option,
and the extended regular expression defined for the
yesexpr locale keyword in the LC_MESSAGES category.
TMPDIR
Determine the path name that provides part of the default
global extended header record file, as described for the
-o globexthdr= keyword as described in the OPTIONS sec‐
tion.
TZ
Determine the timezone used to calculate date and time
strings when the -v option is specified. If TZ is unset
or null, an unspecified default timezone is used.
EXIT STATUS
The following exit values are returned:
0
All files were processed successfully.
>0
An error occurred.
EXTENDED DESCRIPTIONpax Interchange Format
A pax archive tape or file produced in the -xpax format contains a
series of blocks. The physical layout of the archive is identical to
the ustar format described in ustar Interchange Format. Each file
archived is represented by the following sequence:
o An optional header block with extended header records. This
header block is of the form 27403 with a typeflag value of x
or g. The extended header records is included as the data
for this header block.
o A header block that describes the file. Any fields in the
preceding optional extended header overrides the associated
fields in this header block for this file.
o Zero or more blocks that contain the contents of the file.
At the end of the archive file there are two 512-byte blocks filled
with binary zeroes, interpreted as an end-of-archive indicator.
The following is a schematic of an example archive with global extended
header records and two actual files in pax format archive. In the exam‐
ple, the second file in the archive has no extended header preceding
it, presumably because it has no need for extended attributes.
Description Block
Global Extended Header ustar Header [typeflag=g]
Global Extended Header Data
File 1: Extended Header is included ustar Header [typeflag=x]
Extended Header Data
[typeflag=0]
ustar Header Data for File 1
File 2: No Extended Header is included ustar Header [typeflag=0]
Data for File2
End of Archive Indicator Block of binary zeros
Block of binary zeros
pax Header Block
The pax header block is identical to the ustar header block described
in ustar Interchange Format except that two additional typeflag values
are defined:
g
Represents global extended header records for the following files
in the archive. The format of these extended header records are as
described in pax Extended Header. Each value affects all subse‐
quent files that do not override that value in their own extended
header record and until another global extended header record is
reached that provides another value for the same field. The type‐
flag g global headers should not be used with interchange media
that could suffer partial data loss in transporting the archive.
x
Represents extended header records for the following file in the
archive (which has its own ustar header block). The format of
these extended header records is as described in pax Extended
Header.
For both of these types, the size field is the size of the extended
header records in octets. The other fields in the header block are not
meaningful to this version of pax. However, if this archive is read by
pax conforming to a previous version of ISO POSIX-2:1993 Standard, the
header block fields are used to create a regular file that contains the
extended header records as data. Therefore, header block field values
should be selected to provide reasonable file access to this regular
file.
A further difference from the ustar header block is that data blocks
for files of typeflag 1 (the digit one) (hard link) might be included,
which means that the size field can be greater than zero. Archives cre‐
ated by pax-o linkdata includes these data blocks with the hard links.
pax Extended Header
A pax extended header contains values that are inappropriate for the
ustar header block because of limitations in that format: fields
requiring a character encoding other than that described in the ISO/IEC
646: 1991 standard, fields representing file attributes not described
in the ustar header, and fields whose format or length do not fit the
requirements of the ustar header. The values in an extended header add
attributes to the specified file or files or override values in the
specified header blocks, as indicated in the following list of key‐
words. See the description of the typeflag g header block.
An extended header consists of one or more records, each constructed as
follows:
"%d %s=%s\n", length, keyword, value
The extended header records are encoded according to the ISO/IEC
10646-1: 2000 standard (UTF-8). length, BLANK, equals sign (=), and
NEWLINE are limited to the portable character set, as encoded in UTF-8.
keyword and value can be any UTF-8 characters. length is the decimal
length of the extended header record in octets, including the trailing
NEWLINE.
keyword is one of the entries from the following list or a keyword pro‐
vided as an implementation extension. Keywords consisting entirely of
lowercase letters, digits, and periods are reserved for future stan‐
dardization. A keyword does not include an equals sign.
In the following list, the notation of file(s) or block(s) are used to
acknowledge that a keyword affects the specified single file after a
typeflag x extended header, but possibly multiple files after typeflag
g. Any requirements in the list for pax to include a record when in
write or copy mode applies only when such a record has not already been
provided through the use of the -o option. When used in copy mode, pax
behaves as if an archive had been created with applicable extended
header records and then extracted.
atime
The file access time for the specified files, equiva‐
lent to the value of the st_atime member of the stat
structure for a file, as described by the stat(2) func‐
tion. The access time (atime) is restored if the
process has the appropriate privilege required to do
so. The format of the value is as described in pax
Extended Header File Times.
charset
The name of the character set used to encode the data
in the specified files. The entries in the following
table are defined to refer to known standards; addi‐
tional names can be agreed on between the originator
and recipient.
value Formal Standard
ISO-IR 646 1990 ISO/IEC646:1990
ISO-IR 8859 1 1998 ISO/IEC8859-1:1998
ISO-IR 8859 2 1999 ISO/IEC 8859-2:1999
ISO-IR 8859 3 1999 ISO/IEC 8859-3:1999
ISO-IR 8859 4 1999 ISO/IEC8859-4:1998
ISO-IR 8859 5 1999 ISO/IEC8859-5-1999
ISO-IR 8859 6 1999 ISO/IEC8859-6-1999
ISO-IR 8859 7 1987 ISO/IEC8859-7:1987
ISO-IR 8859 8 1999 ISO/IEC8859-8:1999
ISO-IR 8859 9 1999 ISO/IEC8859-9:1999
ISO-IR 8859 10 1998 ISO/IEC8859-10:1999
ISO-IR 8859 13 1998 ISO/IEC8859-13:1998
ISO-IR 8859 14 1998 ISO/IEC8859-14:1998
ISO-IR 8859 15 1999 ISO/IEC8859-15:1999
ISO-IR 10646 2000 ISO/IEC 10646:2000
ISO-IR 10646 2000 UTF-8 ISO/IEC 10646,UTF-8 encoding
BINARY None
The encoding is included in an extended header for
information only; when pax is used as described in IEEE
Std 1003.1-200x, it does not translate the file data
into any other encoding. The BINARY entry indicates
unencoded binary data. When used in write or copy mode,
it is implementation-defined whether pax includes a
charset extended header record for a file.
comment
A series of characters used as a comment. All charac‐
ters in the value field are ignored by pax.
gid
The group ID of the group that owns the file, expressed
as a decimal number using digits from the ISO/IEC 646:
1991 standard. This record overrides the gid field in
the specified header blocks. When used in write or copy
mode, pax includes a gid extended header record for
each file whose group ID is greater than 2097151 (octal
7777777).
gname
The group of the files, formatted as a group name in
the group database. This record overrides the gid and
gname fields in the specified header blocks, and any
gid extended header record. When used in read, copy, or
list mode, pax translates the name from the UTF-8
encoding in the header record to the character set
appropriate for the group database on the receiving
system. If any of the UTF-8 characters cannot be trans‐
lated, and if the -o invalid=UTF-8 option is not speci‐
fied, the results are implementation-defined. When used
in write or copy mode, pax includes a gname extended
header record for each file whose group name cannot be
represented entirely with the letters and digits of the
portable character set.
linkpath
The pathname of a link being created to another file,
of any type, previously archived. This record overrides
the linkname field in the specified ustar header
blocks. The specified ustar header block determines the
type of link created. If typeflag of the specified
header block is 1, it is a hard link. If typeflag is 2,
it is a symbolic link and the linkpath value is the
contents of the symbolic link. pax translates the name
of the link (contents of the symbolic link) from the
UTF-8 encoding to the character set appropriate for the
local file system. When used in write or copy mode, pax
includes a linkpath extended header record for each
link whose pathname cannot be represented entirely with
the members of the portable character set other than
NULL.
mtime
The pathname of a link being created to another file,
of any type, previously archived. This record overrides
the linkname field in the specified ustar header
blocks. The specified ustar header block determines the
type of link created. If typeflag of the specified
header block is 1, it is a hard link. If typeflag is 2,
it is a symbolic link and the linkpath value is the
contents of the symbolic link. pax translates the name
of the link (contents of the symbolic link) from the
UTF-8 encoding to the character set appropriate for the
local file system. When used in write or copy mode, pax
includes a linkpath extended header record for each
link whose pathname cannot be represented entirely with
the members of the portable character set other than
NULL.
path
The pathname of the specified files. This record over‐
rides the name and prefix fields in the specified
header blocks. pax translates the pathname of the file
from the UTF-8 encoding to the character set appropri‐
ate for the local file system. When used in write or
copy mode, pax includes a path extended header record
for each file whose pathname cannot be represented
entirely with the members of the portable character set
other than NULL.
realtime.any
The keywords prefixed by realtime are reserved for
future standardization.
security.any
The keywords prefixed by security are reserved for
future standardization.
size
The size of the file in octets, expressed as a decimal
number using digits from the ISO/IEC 646: 1991 stan‐
dard. This record overrides the size field in the spec‐
ified header blocks. When used in write or copy mode,
pax includes a size extended header record for each
file with a size value greater than 8589934591 (octal
77777777777).
uid
The user ID of the file owner, expressed as a decimal
number using digits from the ISO/IEC 646:1991 standard.
This record overrides the uid field in the following
header block(s). When used in write or copy mode, pax
includes a uid extended header record for each file
whose owner ID is greater than 2097151 (octal 7777777).
uname
The owner of the specified files, formatted as a user
name in the user database. This record overrides the
uid and uname fields in the specified header blocks,
and any uid extended header record. When used in read,
copy, or list mode, pax translates the name from the
UTF-8 encoding in the header record to the character
set appropriate for the user database on the receiving
system. If any of the UTF-8 characters cannot be trans‐
lated, and if the -o invalid= UTF-8 option is not spec‐
ified, the results are implementation-defined. When
used in write or copy mode, pax includes a uname
extended header record for each file whose user name
cannot be represented entirely with the letters and
digits of the portable character set.
If the value field is zero length, it deletes any header block field,
previously entered extended header value, or global extended header
value of the same name.
If a keyword in an extended header record (or in an -o option-argument)
overrides or deletes a corresponding field in the ustar header block,
pax ignores the contents of that header block field.
Unlike the ustar header block fields, NULLs does not delimit values;
all characters within the value field are considered data for the
field.
pax Extended Header Keyword Precedence
This section describes the precedence in which the various header
records and fields and command line options are selected to apply to a
file in the archive. When pax is used in read or list modes, it deter‐
mines a file attribute in the following sequence:
1. If -o delete=keyword-prefix is used, the affected attributes
is determined from step 7, if applicable, or ignored other‐
wise.
2. If -o keyword:= is used, the affected attributes is ignored.
3. If -o keyword:=value is used, the affected attribute is
assigned the value.
4. If there is a typeflag x extended header record, the
affected attribute is assigned the value. When extended
header records conflict, the last one given in the header
takes precedence.
5. If -o keyword=value is used, the affected attribute is
assigned the value.
6. If there is a typeflag g global extended header record, the
affected attribute is assigned the value. When global
extended header records conflict, the last one given in the
global header takes precedence.
7. Otherwise, the attribute is determined from the ustar header
block.
pax Extended Header File Times
pax writes an mtime record for each file in write or copy modes if the
file's modification time cannot be represented exactly in the ustar
header logical record described in ustar Interchange Format. This can
occur if the time is out of ustar range, or if the file system of the
underlying implementation supports non-integer time granularities and
the time is not an integer. All of these time records are formatted as
a decimal representation of the time in seconds since the Epoch. If a
period (.) decimal point character is present, the digits to the right
of the point represents the units of a sub-second timing granularity,
where the first digit is tenths of a second and each subsequent digit
is a tenth of the previous digit. In read or copy mode, pax truncates
the time of a file to the greatest value that is not greater than the
input header file time. In write or copy mode, pax outputs a time
exactly if it can be represented exactly as a decimal number, and oth‐
erwise generates only enough digits so that the same time is recovered
if the file is extracted on a system whose underlying implementation
supports the same time granularity.
ustar Interchange Format
A ustar archive tape or file contains a series of logical records. Each
logical record is a fixed-size logical record of 512 octets. Although
this format can be thought of as being stored on 9-track industry-stan‐
dard 12.7mm (0.5 in) magnetic tape, other types of transportable media
are not excluded. Each file archived is represented by a header logi‐
cal record that describes the file, followed by zero or more logical
records that give the contents of the file. At the end of the archive
file there are two 512-octet logical records filled with binary zeros,
interpreted as an end-of-archive indicator.
The logical records can be grouped for physical I/O operations, as
described under the -bblocksize and -x ustar options. Each group of
logical records can be written with a single operation equivalent to
the write(2) function. On magnetic tape, the result of this write is a
single tape physical block. The last physical block always is the full
size, so logical records after the two zero logical records can contain
undefined data.
The header logical record is structured as shown in the following ta‐
ble. All lengths and offsets are in decimal.
Table 1 ustar Header Block
Field Name Octet Offset Length (in Octets)
name 0 100
mode 100 8
uid 108 8
gid 116 8
size 124 12
mtime 136 12
chksum 148 8
typeflag 156 1
linkname 157 100
magic 257 6
version 263 2
uname 265 32
gname 297 32
devmajor 329 8
devminor 337 8
prefix 345 155
All characters in the header logical record is represented in the coded
character set of the ISO/IEC 646: 1991 standard. For maximum portabil‐
ity between implementations, names should be selected from characters
represented by the portable filename character set as octets with the
most significant bit zero. If an implementation supports the use of
characters outside of slash and the portable filename character set in
names for files, users, and groups, one or more implementation-defined
encodings of these characters are provided for interchange purposes.
pax never creates filenames on the local system that cannot be accessed
using the procedures described in IEEE Std 1003.1-200x. If a filename
is found on the medium that would create an invalid filename, it is
implementation-defined whether the data from the file is stored on the
file hierarchy and under what name it is stored. pax can choose to
ignore these files as long as it produces an error indicating that the
file is being ignored. Each field within the header logical record is
contiguous; that is, there is no padding used.
Each field within the header logical record is contiguous. There is no
padding used. Each character on the archive medium is stored contigu‐
ously.
The fields magic, uname and gname are character strings, each of which
is terminated by a NULL character. The fields name, linkname, and pre‐
fix are NULL-terminated character strings except when all characters in
the array contain non-NULL characters including the last character. The
version field is two octets containing the characters 00 (zero-zero)
The typeflag contains a single character. All other fields are leading
zero-filled octal numbers using digits from the ISO/IEC 646:1991 stan‐
dard IRV. Each numeric field is terminated by one or more SPACE of NULL
characters.
Each character on the archive medium is stored contiguously. The fields
magic, uname, and gname are character strings each terminated by a NULL
character.
name, linkname, and prefix are NULL-terminated character strings except
when all characters in the array contain non-NULL characters including
the last character. The version field is two octets containing the
characters 00 (zero-zero). The typeflag contains a single character.
All other fields are leading zero-filled octal numbers using digits
from the ISO/IEC 646: 1991 standard IRV. Each numeric field is termi‐
nated by one or more spaces or NULL characters.
The name and the prefix fields produce the pathname of the file. A new
pathname is formed, if prefix is not an empty string (its first charac‐
ter is not NULL), by concatenating prefix (up to the first NULL charac‐
ter), a slash character, and name; otherwise, name is used alone. In
either case, name is terminated at the first NULL character. If prefix
begins with a NULL character, it is ignored. In this manner, pathnames
of at most 256 characters can be supported. If a pathname does not fit
in the space provided, pax notifies the user of the error, and does not
store any part of the file-header or data-on the medium.
The linkname field does not use the prefix to produce a pathname. As
such, a linkname is limited to 100 characters. If the name does not fit
in the space provided, pax notifies the user of the error, and does not
attempt to store the link on the medium. The mode field provides 12
bits encoded in the ISO/IEC 646: 1991 standard octal digit representa‐
tion. The encoded bits represent the following values in the ustar mode
field:
Bit Value IEE Std 1003.1-2001 Bit Description
04000 S_ISUID Set UID on execution
02000 S_ISGID Set GID on exectution
01000 reserved Reserved for future standardization
00400 S_IRUSR Read permission for file owner class
00200 S_IWUSR Write permission for file owner class
00100 S_IXUSR Execute/search permission for file
owner class
00040 S_IRGRP Read permission for file group class
00020 S_IWGRP Write permission for file group class
00010 S_IXGRP Execute/search permission for file
group class
00004 S_IROTH Read permission for file other class
00002 S_IWOTH Write permission for file other class
00001 S_IXOTH Execute/search permission for file
other class
When appropriate privilege is required to set one of these mode bits,
and the user restoring the files from the archive does not have the
appropriate privilege, the mode bits for which the user does not have
appropriate privilege are ignored. Some of the mode bits in the archive
format are not mentioned elsewhere in volume IEEE Std 1003.1-200x. If
the implementation does not support those bits, they can be ignored.
The uid and gid fields are the user and group ID of the owner and group
of the file, respectively.
The size field is the size of the file in octets. If the typeflag field
is set to specify a file to be of type 1 (a link) or 2 (a symbolic
link), the size field is specified as zero. If the typeflag field is
set to specify a file of type 5 (directory), the size field is inter‐
preted as described under the definition of that record type. No data
logical records are stored for types 1, 2, or 5. If the typeflag field
is set to 3 (character special file), 4 (block special file), or 6
(FIFO), the meaning of the size field is unspecified by volume IEEE Std
1003.1-200x, and no data logical records is stored on the medium. Addi‐
tionally, for type 6, the size field is ignored when reading. If the
typeflag field is set to any other value, the number of logical records
written following the header is (size+511)/512, ignoring any fraction
in the result of the division.
The mtime field is the modification time of the file at the time it was
archived. It is the ISO/IEC 646: 1991 standard representation of the
octal value of the modification time obtained from the stat() function.
The chksum field is the ISO/IEC 646: 1991 standard IRV representation
of the octal value of the simple sum of all octets in the header logi‐
cal record. Each octet in the header is treated as an unsigned value.
These values are added to an unsigned integer, initialized to zero, the
precision of which is not less than 17 bits. When calculating the
checksum, the chksum field is treated as if it were all spaces.
The typeflag field specifies the type of file archived. If a particular
implementation does not recognize the type, or the user does not have
appropriate privilege to create that type, the file is extracted as if
it were a regular file if the file type is defined to have a meaning
for the size field that could cause data logical records to be written
on the medium. If conversion to a regular file occurs, pax produces an
error indicating that the conversion took place. All of the typeflag
fields are coded in the ISO/IEC 646: 1991 standard IRV:
0
Represents a regular file. For backward compatibility,
a typeflag value of binary zero ('\0') should be rec‐
ognized as meaning a regular file when extracting
files from the archive. Archives written with this
version of the archive file format create regular
files with a typeflag value of the ISO/IEC 646: 1991
standard IRV '0'.
1
Represents a file linked to another file, of any type,
previously archived. Such files are identified by
each file having the same device and file serial num‐
ber. The linked-to name is specified in the linkname
field with a NULL-character terminator if it is less
than 100 octets in length.
2
Represents a symbolic link. The contents of the sym‐
bolic link are stored in the linkname field.
3,4
Represents character special files and block special
files respectively. In this case the devmajor and
devminor fields contain information defining the
device, the format of which is unspecified by volume
IEEE Std 1003.1-200x. Implementations can map the
device specifications to their own local specification
or can ignore the entry.
5
Specifies a directory or subdirectory. On systems
where disk allocation is performed on a directory
basis, the size field contain the maximum number of
octets (which can be rounded to the nearest disk block
allocation unit) that the directory can hold. A size
field of zero indicates no such limiting. Systems
that do not support limiting in this manner should
ignore the size field.
6
Specifies a FIFO special file. The archiving of a FIFO
file archives the existence of this file and not its
contents.
7
Reserved to represent a file to which an implementa‐
tion has associated some high- performance attribute.
Implementations without such extensions should treat
this file as a regular file (type 0).
A-Z
The letters A through Z inclusive are reserved for
custom implementations. All other values are reserved
for future versions of IEEE Std 1003.1-200x.
SUN.devmajor
A Solaris extension to pax extended header keywords.
Specifies the major device number of the file.
When used in write or copy mode and the xustar or pax
format (see -x format) was specified, pax includes a
SUN.devmajor extended header record for each file
whose major device number is too large to fit in 8
octets.
SUN.devminor
A Solaris extension to pax extended header keywords.
Specifies the minor device number of the file.
When used in write or copy mode and the xustar or pax
format (see -x format) is specified, pax includes a
SUN.devminor extended header record for each file
whose minor device number is too large to fit in 8
octets.
SUN.holesdata
A Solaris extension to pax extended header keywords.
Specifies the data and hole pairs for a sparse file.
In write or copy modes and when the xustar or pax for‐
mat (see -x format) is specified, pax includes a
SUN.holesdate extended header record if the underlying
file system supports the detection of files with holes
(see fpathconf(2)) and reports that there is at least
one hole in the file being archived. value consists of
two or more consecutive entries of the following form:
SPACEdata_offsetSPACEhole_offset
where the data and hole offsets are the long values
returned by passing SEEK_DATA and SEEK_HOLE to
lseek(2), respectively. For example, the following
entry is an example of the SUN.holesdata entry in the
extended header for a file with data offsets at bytes
0, 24576, and 49152, and hole offsets at bytes 8192,
32768, and 49159: 49 SUN.holesdata= 0 8192 24576 32768
49152 49159:
49 SUN.holesdata= 0 8192 24576 32768 49152 49159
When extracting a file from an archive in read or copy
modes, if a SUN.holesdata = pair is found in the
extended header for the file, then the file is
restored with the holes identified using this data.
For example, for the SUN.holesdata provided in the
example above, bytes from 0 to 8192 are restored as
data, a hole is created up to the next data position
(24576), bytes 24576 to 32768 is restored as data, and
so forth.
X
A Solaris custom typeflag implementation which speci‐
fies an xustar format (see -x format) extended header.
The typeflag 'x' extended header is treated as a ustar
typeflag 'x' extended header.
E
A Solaris custom typeflag implementation which speci‐
fies an extended attributes header. See fsattr(5).
Attempts to archive a socket using ustar interchange format produce a
diagnostic message. Handling of other file types is implementation-
defined.
The magic field is the specification that this archive was output in
this archive format. If this field contains ustar (the five characters
from the ISO/IEC 646: 1991 standard IRV shown followed by NULL), the
uname and gname fields contain the ISO/IEC 646: 1991 standard IRV rep‐
resentation of the owner and group of the file, respectively (truncated
to fit, if necessary). When the file is restored by a privileged, pro‐
tection-preserving version of the utility, the user and group databases
are scanned for these names. If found, the user and group IDs contained
within these files are used rather than the values contained within the
uid and gid fields.
cpio Interchange Format
The octet-oriented cpio archive format are a series of entries, each
comprising a header that describes the file, name of the file, and con‐
tents of the file.
An archive can be recorded as a series of fixed-size blocks of octets.
This blocking is be used only to make physical I/O more efficient. The
last group of blocks are always at the full size.
For the octet-oriented cpio archive format, the individual entry infor‐
mation are in the order indicated and described by the following table:
Octet-Oriented cpio Archive Entry. See the cpio.h header for additional
details.
Header Field Name Length (in Octets) Interpreted as
c_magic 6 Octal number
c_dev 6 Octal number
c_ino 6 Octal number
c_mode 6 Octal number
c_uid 6 Octal number
c_gid 6 Octal number
c_nlink 6 Octal number
c_rdev 6 Octal number
c_mtime 11 Octal number
c_namesize 6 Octal number
c_filesize 11 Octal number
Filename Field Name Length Interpreted as
c_name c_namesize Pathname string
Filename Field Name Length Interpreted as
c_filedata c_filesize Data
cpio Header
For each file in the archive, a header as defined previously written.
The information in the header fields is written as streams of the
ISO/IEC 646: 1991 standard characters interpreted as octal numbers. The
octal numbers are extended to the necessary length by appending the
ISO/IEC 646: 1991 standard IRV zeros at the most-significant-digit end
of the number. The result is written to the most-significant digit of
the stream of octets first. The fields are interpreted as follows:
c_magic
Identifies the archive as being a transportable archive
by containing the identifying value "070707".
c_dev,c_ino
Contains values that uniquely identify the file within
the archive (that is, no files contain the same pair of
c_dev and c_ino values unless they are links to the same
file). The values are determined in an unspecified man‐
ner.
c_mode
Contains the file type and access permissions as defined
in the following table.
Directories, FIFOs, symbolic links, and regular files
are supported on a system conforming to volume IEEE Std
1003.1-200x; additional values defined previously are
reserved for compatibility with existing systems. Addi‐
tional file types can be supported. Such files should
not be written to archives intended to be transported to
other systems.
File Permissions Name Value Indicates
C_IRUSR 000400 by owner
C_IWUSR 000200 by owner
C_IXUSR 000100 by owner
C_IRGRP 000040 by group
CW_IWFGP 000020 by group
CW_IXGRP 000010 by group
CW_IROTH 000004 by others
CW_IWOTH 000002 by others
CW_IXOTH 000001 by others
CW_ISUID 004000 Set uid
W_ISGID 002000 Set gid
W_ISVTX 001000 Reserved
File Type Name Value Indicates
C_ISDIR 040000 Directory
C_ISFIFO 010000 FIFO
C_ISREG 0100000 Regular file
C_ISLNK 0120000 Symbolic link
C_ISBLK 060000 Block special file
C_ISCHR 020000 Character special file
C_ISSOCK 0140000 Socket
C_ISCTG 0110000 Reserved
c_uid
Contains the user ID of the owner.
c_gid
Contains the group ID of the group
c_nlink
Contains a number greater than or equal to the number of
links in the archive referencing the file. If the -a
option is used to append to a cpio archive, pax does
need not to account for the files in the existing part
of the archive when calculating the c_nlink values for
the appended part of the archive. It does also need not
alter the c_nlink values in the existing part of the ar‐
chive if additional files with the same c_dev and c-ino
values are appended to the archive.
c_rdev
Contains implementation-defined information for charac‐
ter or block special files.
c_mtime
Contains the latest time of modification of the file at
the time the archive was created.
c_namesize
Contains the length of the pathname, including the ter‐
minating NULL character.
c_filesize
Contains the length of the file in octets. This is the
length of the data section following the header struc‐
ture.
cpio Filename
The c_name field contains the pathname of the file. The length of this
field in octets is the value of c_namesize. If a filename is found on
the medium that would create an invalid pathname, it is implementation-
defined whether the data from the file is stored on the file hierarchy
and under what name it is stored. All characters are represented in the
ISO/IEC 646: 1991 standard IRV. For maximum portability between imple‐
mentations, names should be selected from characters represented by the
portable filename character set as octets with the most significant bit
zero. If an implementation supports the use of characters outside the
portable filename character set in names for files, users, and groups,
one or more implementation-defined encodings of these characters are
provided for interchange purposes.pax does not create filenames on the
local system that cannot be accessed by way of the procedures described
in volume IEEE Std 1003.1-200x. If a filename is found on the medium
that would create an invalid filename, it is implementation-defined
whether the data from the file is stored on the local file system and
under what name it is stored. pax can choose to ignore these files as
long as it produces an error indicating that the file is being ignored.
cpio File Data
Following c_name, there is c_filesize octets of data. Interpretation
of such data occurs in a manner dependent on the file. If c_filesize is
zero, no data is contained in c_filedata . When restoring from an ar‐
chive:
o If the user does not have the appropriate privilege to cre‐
ate a file of the specified type, pax ignores the entry and
writes an error message to standard error.
o Only regular files have data to be restored. Presuming a
regular file meets any selection criteria that might be
imposed on the format-reading utility by the user, such data
is restored.
o If a user does not have appropriate privilege to set a par‐
ticular mode flag, the flag is ignored. Some of the mode
flags in the archive format are not mentioned in volume IEEE
Std 1003.1-200x. If the implementation does not support
those flags, they can be ignored.
cpio Special Entries
FIFO special files, directories, and the trailer are recorded with
c_filesize equal to zero. For other special files, c_filesize is
unspecified in volume IEEE Std 1003.1-200x. The header for the next
file entry in the archive are written directly after the last octet of
the file entry preceding it. A header denoting the filename trailer
indicates the end of the archive; the contents of octets in the last
block of the archive following such a header are undefined.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬───────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼───────────────────┤
│Interface Stability │ Committed │
├────────────────────┼───────────────────┤
│Standard │ See standards(5). │
└────────────────────┴───────────────────┘
SEE ALSOchmod(1), cpio(1), ed(1), printf(1), tar(1), mkdir(2), lseek(2),
stat(2), write(2), archives.h(3HEAD), attributes(5), environ(5),
fnmatch(5), formats(5)fsattr(5), largefile(5), regex(5), standards(5)
IEEE Std 1003.1-200x, ISO/IEC 646: 1991, ISO POSIX-2:1993 Standard
Jul 16, 2008 PAX(1)
