pax.1

早期freebsd实现

duplicated or conflict with each other, the one(s) given last will take
precedence.
For example, if
.Dl Fl p Ar eme
is specified, file modification times are still preserved.
.It Fl s Ar replstr
Modify the file or archive member names specified by the
.Ar pattern
or
.Ar file
operands according to the substitution expression
.Ar replstr ,
using the syntax of the
.Xr ed 1
utility regular expressions.
The format of these regular expressions are:
.Dl /old/new/[gp]
As in
.Xr ed 1 ,
.Cm old
is a basic regular expression and
.Cm new
can contain an ampersand (&), \\n (where n is a digit) back-references,
or subexpression matching.
The
.Cm old
string may also contain
.Dv <newline>
characters.
Any non-null character can be used as a delimiter (/ is shown here).
Multiple
.Fl s
expressions can be specified.
The expressions are applied in the order they are specified on the
command line, terminating with the first successful substitution.
The optional trailing
.Cm 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
.Cm g
option.
The optional trailing
.Cm p
will cause the final result of a successful substitution to be written to
.Dv standard error
in the following format:
.Dl <original pathname> >> <new pathname>
File or archive member names that substitute to the empty string
are not selected and will be skipped.
.It Fl t
Reset the access times of any file or directory read or accessed by
.Nm pax
to be the same as they were before being read or accessed by
.Nm pax .
.It Fl u
Ignore files that are older (having a less recent file modification time)
than a pre-existing file or archive member with the same name.
During
.Em 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
.Em 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
.Em 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.
.It Fl v
During a
.Em list
operation, produce a verbose table of contents using the format of the
.Xr ls 1
utility with the
.Fl l
option.
For pathnames representing a hard link to a previous member of the archive,
the output has the format:
.Dl <ls -l listing> == <link name>
For pathnames representing a symbolic link, the output has the format:
.Dl <ls -l listing> => <link name>
Where <ls -l listing> is the output format specified by the 
.Xr ls 1
utility when used with the
.Fl l
option.
Otherwise for all the other operational modes (
.Em read , write ,
and
.Em copy ) ,
pathnames are written and flushed to
.Dv standard error
without a trailing
.Dv <newline>
as soon as processing begins on that file or
archive member.
The trailing
.Dv <newline> ,
is not buffered, and is written only after the file has been read or written.
.It Fl x Ar format
Specify the output archive format, with the default format being
.Ar ustar .
.Nm Pax
currently supports the following formats:
.Bl -tag -width "sv4cpio"
.It Ar cpio
The extended cpio interchange format specified in the
.St -p1003.2
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
.Nm pax
and is repaired.
.It Ar 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
.Nm pax
and is repaired.
.It Ar 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
.Nm pax
and is repaired.
.It Ar 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
.Nm pax
and is repaired.
.It Ar 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.
Only
.Em regular
files,
.Em  hard links , soft links ,
and
.Em  directories
will be archived (other file system types are not supported).
For backwards compatibility with even older tar formats, a
.Fl o
option can be used when writing an archive to omit the storage of directories.
This option takes the form:
.Dl Fl o Cm write_opt=nodir
.It Ar ustar
The extended tar interchange format specified in the
.St -p1003.2
standard.
The default blocksize for this format is 10240 bytes.
Pathnames stored by this format must be 250 characters or less in length.
.El
.Pp
.Nm Pax
will detect and report any file that it is unable to store or extract
as the result of any specific archive format restrictions.
The individual archive formats may impose additional restrictions on use.
Typical archive format restrictions include (but are not limited to):
file pathname length, file size, link pathname length and the type of the file.
.It Fl B Ar bytes
Limit the number of bytes written to a single archive volume to
.Ar bytes .
The
.Ar bytes
limit can end with
.Li m ,
.Li k ,
or
.Li b
to specify multiplication by 1048576 (1M), 1024 (1K) or 512, respectively.
A pair of
.Ar bytes
limits can be separated by
.Li x
to indicate a product.
.Pp
.Em Warning :
Only use this option when writing an archive to a device which supports
an end of file read condition based on last (or largest) write offset
(such as a regular file or a tape drive). 
The use of this option with a floppy or hard disk is not recommended.
.It Fl D
This option is the same as the
.Fl 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
.Ar directory .
.It Fl E Ar limit
Limit the number of consecutive read faults while trying to read a flawed
archives to
.Ar limit .
With a positive
.Ar limit ,
.Nm pax
will attempt to recover from an archive read error and will
continue processing starting with the next file stored in the archive.
A
.Ar limit
of 0 will cause
.Nm pax
to stop operation after the first read error is detected on an archive volume.
A
.Ar limit
of
.Li NONE
will cause
.Nm pax 
to attempt to recover from read errors forever.
The default 
.Ar limit
is a small positive number of retries.
.Pp
.Em Warning: 
Using this option with
.Li NONE
should be used with extreme caution as
.Nm pax
may get stuck in an infinite loop on a very badly flawed archive.
.It Fl G Ar group
Select a file based on its
.Ar group
name, or when starting with a
.Cm # ,
a numeric gid.
A '\\' can be used to escape the
.Cm # .
Multiple 
.Fl G
options may be supplied and checking stops with the first match.
.It Fl H
Follow only command line symbolic links while performing a physical file
system traversal.
.It Fl L
Follow all symbolic links to perform a logical file system traversal.
.It Fl P
Do not follow symbolic links, perform a physical file system traversal.
This is the default mode.
.It Fl T Ar [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 
.Ar from_date
to
.Ar to_date
(the dates are inclusive).
If only a 
.Ar from_date
is supplied, all files with a modification or inode change time
equal to or younger are selected.
If only a
.Ar to_date
is supplied, all files with a modification or inode change time
equal to or older will be selected.
When the 
.Ar from_date
is equal to the
.Ar to_date ,
only files with a modification or inode change time of exactly that
time will be selected.
.Pp
When
.Nm pax
is in the 
.Em write
or
.Em copy
mode, the optional trailing field
.Ar [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
.Ar m
specifies the comparison of file modification time (the time when
the file was last written).
The
.Ar 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 
.Ar c
and
.Ar 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
.Nm pax
is used to create a time based incremental archive (only files that were
changed during a specified time range will be archived).
.Pp
A time range is made up of six different fields and each field must contain two
digits.
The format is:
.Dl [yy[mm[dd[hh]]]]mm[.ss]
Where
.Cm yy
is the last two digits of the year,
the first
.Cm mm
is the month (from 01 to 12),
.Cm dd
is the day of the month (from 01 to 31),
.Cm hh
is the hour of the day (from 00 to 23),
the second
.Cm mm
is the minute (from 00 to 59),
and
.Cm ss
is the seconds (from 00 to 59).
The minute field
.Cm mm
is required, while the other fields are optional and must be added in the
following order:
.Dl Cm hh , dd , mm , yy .
The 
.Cm ss
field may be added independently of the other fields.
Time ranges are relative to the current time, so
.Dl Fl T Ar 1234/cm
would select all files with a modification or inode change time
of 12:34 PM today or later.
Multiple 
.Fl T
time range can be supplied and checking stops with the first match.
.It Fl U Ar user
Select a file based on its
.Ar user
name, or when starting with a
.Cm # ,
a numeric uid.
A '\\' can be used to escape the
.Cm # .
Multiple 
.Fl U
options may be supplied and checking stops with the first match.
.It Fl X
When traversing the file hierarchy specified by a pathname,
do not descend into directories that have a different device ID.
See the
.Li st_dev 
field as described in
.Xr stat 2
for more information about device ID's.
.It Fl Y
This option is the same as the
.Fl D
option, except that the inode change time is checked using the
pathname created after all the file name modifications have completed.
.It Fl Z
This option is the same as the
.Fl u
option, except that the modification time is checked using the
pathname created after all the file name modifications have completed.
.El
.Pp
The options that operate on the names of files or archive members (
.Fl c ,
.Fl i ,
.Fl n ,
.Fl s ,
.Fl u ,
.Fl v ,
.Fl D ,
.Fl G ,
.Fl T ,
.Fl U ,
.Fl Y ,
and
.Fl Z )
interact as follows.
.Pp
When extracting files during a
.Em read
operation, archive members are
.Sq selected ,
based only on the user specified pattern operands as modified by the
.Fl c ,
.Fl n ,
.Fl u ,
.Fl D ,
.Fl G ,
.Fl T ,
.Fl U
options.
Then any
.Fl s
and
.Fl i
options will modify in that order, the names of these selected files.
Then the
.Fl Y
and
.Fl Z
options will be applied based on the final pathname.
Finally the 
.Fl v
option will write the names resulting from these modifications.
.Pp
When archiving files during a
.Em write
operation, or copying files during a
.Em copy
operation, archive members are
.Sq selected ,
based only on the user specified pathnames as modified by the
.Fl n ,
.Fl u ,
.Fl D ,
.Fl G ,
.Fl T ,
and 
.Fl U
options (the
.Fl D
option only applies during a copy operation).
Then any
.Fl s 
and
.Fl i
options will modify in that order, the names of these selected files.
Then during a
.Em copy
operation the
.Fl Y
and the
.Fl Z
options will be applied based on the final pathname.
Finally the
.Fl v
option will write the names resulting from these modifications.
.Pp
When one or both of the
.Fl u
or
.Fl D
options are specified along with the
.Fl n
option, a file is not considered selected unless it is newer
than the file to which it is compared.
.Sh EXAMPLES
The command:
.Dl pax -w -f /dev/rst0 .\ 
copies the contents of the current directory to the device
.Pa /dev/rst0 .
.Pp
The command:
.Dl pax -r -v -f filename
gives the verbose table of contents for an archive stored in
.Pa filename .
.Pp
The following commands:
.Dl mkdir newdir
.Dl cd olddir
.Dl pax -rw .\ newdir
will copy the entire
.Pa olddir
directory hierarchy to
.Pa newdir .
.Pp
The command:
.Dl pax -r -s ',^//*usr//*,,' -f a.pax
reads the archive 
.Pa a.pax ,
with all files rooted in ``/usr'' into the archive extracted relative to the
current directory.
.Pp
The command:
.Dl pax -rw -i .\ dest_dir
can be used to interactively select the files to copy from the current
directory to
.Pa dest_dir .
.Pp
The command:
.Dl pax -r -pe -U root -G bin -f a.pax
will extract all files from the archive
.Pa a.pax
which are owned by
.Em root
with group
.Em bin
and will preserve all file permissions.
.Pp
The command:
.Dl pax -r -w -v -Y -Z home /backup
will update (and list) only those files in the destination directory
.Pa /backup
which are older (less recent inode change or file modification times) than
files with the same name found in the source file tree
.Pa home .
.Sh STANDARDS
The
.Nm pax
utility is a superset of the
.St -p1003.2
standard.
The options
.Fl B ,
.Fl D ,
.Fl E ,
.Fl G ,
.Fl H ,
.Fl L ,
.Fl P ,
.Fl T ,
.Fl U ,
.Fl Y ,
.Fl Z ,
the archive formats
.Ar bcpio ,
.Ar sv4cpio ,
.Ar sv4crc ,
.Ar tar ,
and the flawed archive handling during
.Ar list
and
.Ar read
operations are extensions to the
.Tn POSIX
standard.
.Sh AUTHOR
Keith Muller at the University of California, San Diego
.Sh ERRORS
.Nm pax
will exit with one of the following values:
.Bl -tag -width 2n
.It 0
All files were processed successfully.
.It 1 
An error occurred.
.El
.Pp
Whenever
.Nm 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
.Fl p
option is specified, a diagnostic message is written to
.Dv 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,
.Nm pax
will not create a second copy of the file.
.Pp
If the extraction of a file from an archive is prematurely terminated by
a signal or error,
.Nm 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.
.Pp
If the creation of an archive is prematurely terminated by a signal or error,
.Nm pax
may have only partially created the archive which may violate the specific
archive format specification.
.Pp
If while doing a
.Em copy ,
.Nm pax
detects a file is about to overwrite itself, the file is not copied,
a diagnostic message is written to
.Dv standard error
and when
.Nm pax
completes it will exit with a non-zero exit status.