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 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 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 subse-
             quently 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 status.

     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 opera-
             tion.

     -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 leading 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 immedi-
             ately 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 par-
             ticular 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 stan-
             dard 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 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.

     -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 character-
             istics to be retained or discarded on extraction.  The string
             consists of the specification characters a, e, m, o, and p.  Mul-
             tiple characteristics can be concatenated within the same string
             and multiple -p options can be specified.  The meaning of the
             specification characters are as follows:

             a   Do not preserve file access times.  By default, file access
                 times are preserved whenever possible.

             e   ‘Preserve everything’, the user ID, group ID, file mode bits,
                 file access time, and file modification time.  This is
                 intended to be used by root, someone with all the appropriate
                 privileges, in order to preserve all aspects of the files as
                 they are recorded in the archive.  The e flag is the sum of
                 the o and p flags.

             m   Do not preserve file modification times.  By default, file
                 modification times are preserved whenever possible.

             o   Preserve the user ID and group ID.

             p   ‘Preserve’ the file mode bits.  This intended to be used by a
                 user with regular privileges who wants to preserve all
                 aspects of the file other than the ownership.  The file times
                 are preserved by default, but two other flags are offered to
                 disable this and use the time of extraction instead.

             In the preceding list, ‘preserve’ indicates that an attribute
             stored in the archive is given to the extracted file, subject to
             the permissions of the invoking process.  Otherwise the attribute
             of the extracted file is determined as part of the normal file
             creation action.  If neither the e nor the o specification char-
             acter is specified, or the user ID and group ID are not preserved
             for any reason, pax will not set the S_ISUID (setuid) and S_ISGID
             (setgid) bits of the file mode.  If the preservation of any of
             these items fails for any reason, pax will write a diagnostic
             message to standard error.  Failure to preserve these items will
             affect the final exit status, but will not cause the extracted
             file to be deleted.  If the file characteristic letters in any of
             the string option-arguments are duplicated or conflict with each
             other, the one(s) given last will take precedence.  For example,
             if
                   -p eme
             is specified, file modification times are still preserved.

     -s replstr
             Modify the file or archive member names specified by the pattern
             or file operands according to the substitution expression
             replstr, using the syntax of the ed(1) utility regular 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 substitution
             stops the operation of the g option.  The optional trailing p
             will cause the final result of a successful substitution to be
             written to standard error in the following format:
                   <original pathname> >> <new pathname>
             File or archive member names that substitute to the empty string
             are not selected and will be skipped.

     -t      Reset the access times of any file or directory read or accessed
             by pax to be the same as they were before being read or accessed
             by pax.

     -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 member
             is newer than the file.  During write, a file system member with
             the same name as an archive member will be written to the archive
             if it is newer than the archive member.  During copy, the file in
             the destination hierarchy is replaced by the file in the source
             hierarchy or by a link to the file in the source hierarchy if the
             file in the source hierarchy is newer.

     -v      During a list operation, produce a verbose table of contents
             using the format of the ls(1) utility with the -l option.  For
             pathnames representing a hard link to a previous member of the
             archive, the output has the format:
                   <ls -l listing> == <link name>
             For pathnames representing a symbolic link, the output has the
             format:
                   <ls -l listing> => <link name>
             Where <ls -l listing> is the output format specified by the ls(1)
             utility when used with the -l option.  Otherwise for all the
             other operational modes (read, write, and copy), pathnames are
             written and flushed to standard error without a trailing newline
             as soon as processing begins on that file or archive member.  The
             trailing newline is not buffered and is written only after the
             file has been read or written.

     -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 information
                      about a file (used for detecting file hard links by this
                      format) which may be truncated by this format is
                      detected by pax and is repaired.

             sv4crc   The System V release 4 cpio with file crc checksums.
                      The default blocksize for this format is 5120 bytes.
                      Inode and device information about a file (used for
                      detecting file hard links by this format) which may be
                      truncated by this format is detected by pax and is
                      repaired.

             tar      The old BSD tar format as found in 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 recom-
             mended.

     -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 physi-
             cal 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 sup-
             plied, all files with a modification or inode change time equal
             to or younger are selected.  If only a to_date is supplied, all
             files with a modification or inode change time equal to or older
             will be selected.  When the from_date is equal to the to_date,
             only files with a modification or inode change time of exactly
             that time will be selected.

             When pax is in the write or copy mode, the optional trailing
             field [c][m] can be used to determine which file time (inode
             change, file modification or both) are used in the comparison.
             If neither is specified, the default is to use file modification
             time only.  The m specifies the comparison of file modification
             time (the time when the file was last written).  The c specifies
             the comparison of inode change time (the time when the file inode
             was last changed; e.g., a change of owner, group, mode, etc).
             When c and m are both specified, then the modification and inode
             change times are both compared.  The inode change time comparison
             is useful in selecting files whose attributes were recently
             changed or selecting files which were recently created and had
             their modification time reset to an older time (as what happens
             when a file is extracted from an archive and the modification
             time is preserved).  Time comparisons using both file times is
             useful when pax is used to create a time based incremental
             archive (only files that were changed during a specified time
             range will be archived).

             A time range is made up of six different fields and each field
             must contain two digits.  The format is:
                   [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 information
             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 modifi-
             cation 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 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.


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 hierarchy
     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

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