4.4BSD/usr/share/man/cat1/pax.0
PAX(1) BSD Reference Manual PAX(1)
NNAAMMEE
ppaaxx - read and write file archives and copy directory hierarchies
SSYYNNOOPPSSIISS
ppaaxx [--ccddnnvv] [--ff _a_r_c_h_i_v_e] [--ss _r_e_p_l_s_t_r] _._._. [--UU _u_s_e_r] _._._. [--GG _g_r_o_u_p] _._._.
[--TT [_f_r_o_m___d_a_t_e] [_,_t_o___d_a_t_e]] _._._. [_p_a_t_t_e_r_n _._._.]
ppaaxx --rr [--ccddiikknnuuvvDDYYZZ] [--ff _a_r_c_h_i_v_e] [--oo _o_p_t_i_o_n_s] _._._. [--pp _s_t_r_i_n_g] _._._.
[--ss _r_e_p_l_s_t_r] _._._. [--EE _l_i_m_i_t] [--UU _u_s_e_r] _._._. [--GG _g_r_o_u_p] _._._. [--TT
[_f_r_o_m___d_a_t_e] [_,_t_o___d_a_t_e]] _._._. [_p_a_t_t_e_r_n _._._.]
ppaaxx --ww [--ddiittuuvvHHLLXX] [--bb _b_l_o_c_k_s_i_z_e] [[--aa] [--ff _a_r_c_h_i_v_e]] [--xx _f_o_r_m_a_t]
[--ss _r_e_p_l_s_t_r] _._._. [--oo _o_p_t_i_o_n_s] _._._. [--UU _u_s_e_r] _._._. [--GG _g_r_o_u_p] _._._.
[--BB _b_y_t_e_s] [--TT [_f_r_o_m___d_a_t_e] [_,_t_o___d_a_t_e] [_/_[_c_]_[_m_]]] _._._. [_f_i_l_e _._._.]
ppaaxx --rr --ww [--ddiikkllnnttuuvvDDHHLLXXYYZZ] [--pp _s_t_r_i_n_g] _._._. [--ss _r_e_p_l_s_t_r] _._._. [--UU _u_s_e_r]
_._._. [--GG _g_r_o_u_p] _._._. [--TT [_f_r_o_m___d_a_t_e] [_,_t_o___d_a_t_e] [_/_[_c_]_[_m_]]] _._._. [_f_i_l_e
_._._.] _d_i_r_e_c_t_o_r_y
DDEESSCCRRIIPPTTIIOONN
PPaaxx will read, write, and list the members of an archive file, and will
copy directory hierarchies. PPaaxx supports a wide variety of different
archive formats. These archive formats are described in more detail un-
der the --xx option.
The operand _d_i_r_e_c_t_o_r_y specifies a destination directory pathname. PPaaxx
will exit with a non-zero exit status if the _d_i_r_e_c_t_o_r_y operand does not
exist, or it is not writable by the user, or it is not of type directory.
The operand _p_a_t_t_e_r_n is used to select one or more pathnames of archive
members using the pattern matching notation described by fnmatch(3).
When no _p_a_t_t_e_r_n_s are specified, all members of the archive will be se-
lected. When a _p_a_t_t_e_r_n matches a directory, the entire file hierarchy
rooted at that directory will be selected. If at the completion of oper-
ation a _p_a_t_t_e_r_n operand did not select at least one archive member, ppaaxx
will write these _p_a_t_t_e_r_n operands in a diagnostic message to standard
error and then exit with a non-zero exit status.
The operand _f_i_l_e specifies the pathname of a file to be copied or
archived. If at the completion of operation a _f_i_l_e operand did not se-
lect at least one archived file, ppaaxx will write these _f_i_l_e operand path-
names in a diagnostic message to standard error and then exit with a non-
zero exit status.
PPaaxx operates in one of four operational modes based on the presence of
the --rr and the --ww options. These operational modes are: _l_i_s_t, _r_e_a_d,
_w_r_i_t_e, and _c_o_p_y_.
<none> _L_i_s_t. PPaaxx 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 _p_a_t_t_e_r_n_s_. The table of contents is
written with one filename per line and is not buffered more than
a single line at a time.
--rr _R_e_a_d. PPaaxx extracts the members of the archive file read from the
standard input, with pathnames matching the specified _p_a_t_t_e_r_n_s_.
The format and the blocking of the archive is automatically de-
termined 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 hierar-
chy. The ownership, access and modification times, and file mode
of the extracted files are discussed in more detail under the --pp
option.
--ww _W_r_i_t_e. PPaaxx writes an archive containing the _f_i_l_e operands to
standard output using the specified archive format. When no _f_i_l_e
operands are specified, a list of files to copy, one per line, is
read from standard input. A _f_i_l_e operand that is also a directory
will include the entire file hierarchy rooted at that directory.
--rr --ww _C_o_p_y. PPaaxx copies the _f_i_l_e operands to the destination _d_i_r_e_c_t_o_r_y.
When no _f_i_l_e operands are specified, a list of files to copy, one
per line, is read from the standard input. A _f_i_l_e operand that is
also a directory will include the entire file hierarchy rooted at
that directory. The effect of the _c_o_p_y is as if the copied files
were written to an archive file and then subsequently extracted,
except that there may be hard links between the original and the
copied files (see the --ll option below).
_W_a_r_n_i_n_g: The destination _d_i_r_e_c_t_o_r_y must not be one of the _f_i_l_e
operands or a member of a file hierarchy rooted at one of the
_f_i_l_e operands. The result of a _c_o_p_y under these conditions is
unpredictable.
While processing a damaged archive during a _r_e_a_d or _l_i_s_t operation, ppaaxx
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 --EE option for more details on error handling).
OOPPTTIIOONNSS
The following options are supported:
--rr Read an archive file from standard input and extract the specified
_f_i_l_e_s. If any intermediate directories are needed in order to ex-
tract 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, ppaaxx
will write a diagnostic message to standard error and exit with a
non-zero exit status at the completion of operation.
--ww Write files to the standard output in the specified archive format.
When no _f_i_l_e operands are specified, standard input is read for a
list of pathnames, one per line, without any leading or trailing
<blanks>.
--aa Append _f_i_l_e_s to the end of an archive that was previously written.
If an archive format is not specified with a --xx 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 al-
ready used in the archive will cause ppaaxx to exit immediately with a
non-zero exit status. The blocking size used in the archive volume
where writing starts will continue to be used for the remainder of
that archive volume.
_W_a_r_n_i_n_g: Many storage devices are not able to support the opera-
tions necessary to perform an append operation. Any attempt to ap-
pend to an archive stored on such a device may damage the archive
or have other unpredictable results. Tape drives in particular are
more likely to not support an append operation. An archive stored
in a regular file system file or on a disk device will usually sup-
port an append operation.
--bb _b_l_o_c_k_s_i_z_e
When _w_r_i_t_i_n_g an archive, block the output at a positive decimal in-
teger number of bytes per write to the archive file. The _b_l_o_c_k_s_i_z_e
must be a multiple of 512 bytes with a maximum of 32256 bytes. A
_b_l_o_c_k_s_i_z_e can end with k or b to specify multiplication by 1024
(1K) or 512, respectively. A pair of _b_l_o_c_k_s_i_z_e_s 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 _b_l_o_c_k_s_i_z_e is dependent
on the specific archive format being used (see the --xx option).
--cc Match all file or archive members _e_x_c_e_p_t those specified by the
_p_a_t_t_e_r_n and _f_i_l_e operands.
--dd Cause files of type directory being copied or archived, or archive
members of type directory being extracted, to match only the direc-
tory file or archive member and not the file hierarchy rooted at
the directory.
--ff _a_r_c_h_i_v_e
Specify _a_r_c_h_i_v_e as the pathname of the input or output archive,
overriding the default standard input (for _l_i_s_t and _r_e_a_d) or
standard output (for _w_r_i_t_e). A single archive may span multiple
files and different archive devices. When required, ppaaxx will
prompt for the pathname of the file or device of the next volume in
the archive.
--ii Interactively rename files or archive members. For each archive
member matching a _p_a_t_t_e_r_n operand or each file matching a _f_i_l_e
operand, ppaaxx will prompt to _/_d_e_v_/_t_t_y giving the name of the file,
its file mode and its modification time. PPaaxx will then read a line
from _/_d_e_v_/_t_t_y. 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. Oth-
erwise, its name is replaced with the contents of the line. PPaaxx
will immediately exit with a non-zero exit status if <EOF> is en-
countered when reading a response or if _/_d_e_v_/_t_t_y cannot be opened
for reading and writing.
--kk Do not overwrite existing files.
--ll Link files. (The letter ell). In the _c_o_p_y mode ( --rr --ww), hard
links are made between the source and destination file hierarchies
whenever possible.
--nn Select the first archive member that matches each _p_a_t_t_e_r_n operand.
No more than one archive member is matched for each _p_a_t_t_e_r_n. When
members of type directory are matched, the file hierarchy rooted at
that directory is also matched (unless --dd is also specified).
--oo _o_p_t_i_o_n_s
Information to modify the algorithm for extracting or writing
archive files which is specific to the archive format specified by
--xx. In general, _o_p_t_i_o_n_s take the form: nnaammee==vvaalluuee
--pp _s_t_r_i_n_g
Specify one or more file characteristic options (privileges). The
_s_t_r_i_n_g option-argument is a string specifying file characteristics
to be retained or discarded on extraction. The string consists of
the specification characters aa, ee, mm, oo, and pp. Multiple character-
istics can be concatenated within the same string and multiple --pp
options can be specified. The meaning of the specification charac-
ters are as follows:
aa Do not preserve file access times. By default, file access
times are preserved whenever possible.
ee `Preserve everything', the user ID, group ID, file mode bits,
file access time, and file modification time. This is intended
to be used by _r_o_o_t, someone with all the appropriate privi-
leges, in order to preserve all aspects of the files as they
are recorded in the archive. The ee flag is the sum of the oo
and pp flags.
mm Do not preserve file modification times. By default, file mod-
ification times are preserved whenever possible.
oo Preserve the user ID and group ID.
pp `Preserve' the file mode bits. This intended to be used by a
_u_s_e_r with regular privileges who wants to preserve all aspects
of the file other than the ownership. The file times are pre-
served 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 cre-
ation action. If neither the ee nor the oo specification character
is specified, or the user ID and group ID are not preserved for any
reason, ppaaxx will not set the S_ISUID (_s_e_t_u_i_d) and S_ISGID (_s_e_t_g_i_d)
bits of the file mode. If the preservation of any of these items
fails for any reason, ppaaxx will write a diagnostic message to
standard error. Failure to preserve these items will affect the fi-
nal exit status, but will not cause the extracted file to be delet-
ed. If the file characteristic letters in any of the string op-
tion-arguments are duplicated or conflict with each other, the
one(s) given last will take precedence. For example, if
--pp _e_m_e
is specified, file modification times are still preserved.
--ss _r_e_p_l_s_t_r
Modify the file or archive member names specified by the _p_a_t_t_e_r_n or
_f_i_l_e operands according to the substitution expression _r_e_p_l_s_t_r, us-
ing the syntax of the ed(1) utility regular expressions. The for-
mat of these regular expressions are:
/old/new/[gp]
As in ed(1), oolldd is a basic regular expression and nneeww can contain
an ampersand (&), \n (where n is a digit) back-references, or
subexpression matching. The oolldd string may also contain <newline>
characters. Any non-null character can be used as a delimiter (/
is shown here). Multiple --ss expressions can be specified. The ex-
pressions are applied in the order they are specified on the com-
mand line, terminating with the first successful substitution. The
optional trailing gg 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 gg option. The
optional trailing pp will cause the final result of a successful
substitution to be written to standard error in the following for-
mat:
<original pathname> >> <new pathname>
File or archive member names that substitute to the empty string
are not selected and will be skipped.
--tt Reset the access times of any file or directory read or accessed by
ppaaxx to be the same as they were before being read or accessed by
ppaaxx.
--uu 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 _r_e_a_d, 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 _w_r_i_t_e, 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 _c_o_p_y, the file in the desti-
nation 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.
--vv During a _l_i_s_t operation, produce a verbose table of contents using
the format of the ls(1) utility with the --ll 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 for-
mat:
<ls -l listing> => <link name>
Where <ls -l listing> is the output format specified by the ls(1)
utility when used with the --ll option. Otherwise for all the other
operational modes ( _r_e_a_d, _w_r_i_t_e, and _c_o_p_y), 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.
--xx _f_o_r_m_a_t
Specify the output archive format, with the default format being
_u_s_t_a_r. PPaaxx currently supports the following formats:
_c_p_i_o The extended cpio interchange format specified in the IEEE
Std1003.2 (``POSIX'') 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 ppaaxx and is repaired.
_b_c_p_i_o 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 ppaaxx and is
repaired.
_s_v_4_c_p_i_o 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 ppaaxx and is repaired.
_s_v_4_c_r_c 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 ppaaxx and is repaired.
_t_a_r 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 _r_e_g_u_l_a_r files, _h_a_r_d _l_i_n_k_s, _s_o_f_t _l_i_n_k_s, and
_d_i_r_e_c_t_o_r_i_e_s will be archived (other file system types are
not supported). For backwards compatability with even
older tar formats, a --oo option can be used when writing an
archive to omit the storage of directories. This option
takes the form:
--oo wwrriittee__oopptt==nnooddiirr
_u_s_t_a_r The extended tar interchange format specified in the IEEE
Std1003.2 (``POSIX'') standard. The default blocksize for
this format is 10240 bytes. Pathnames stored by this for-
mat must be 250 characters or less in length.
PPaaxx 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.
--BB _b_y_t_e_s
Limit the number of bytes written to a single archive volume to
_b_y_t_e_s. The _b_y_t_e_s limit can end with m, k, or b to specify multipli-
cation by 1048576 (1M), 1024 (1K) or 512, respectively. A pair of
_b_y_t_e_s limits can be separated by x to indicate a product.
_W_a_r_n_i_n_g: Only use this option when writing a 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 recommend-
ed.
--DD This option is the same as the --uu option, except that the file in-
ode 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 _d_i_r_e_c_t_o_r_y.
--EE _l_i_m_i_t
Limit the number of consecutive read faults while trying to read a
flawed archives to _l_i_m_i_t. With a positive _l_i_m_i_t, ppaaxx will attempt
to recover from an archive read error and will continue processing
starting with the next file stored in the archive. A _l_i_m_i_t of 0
will cause ppaaxx to stop operation after the first read error is de-
tected on an archive volume. A _l_i_m_i_t of NONE will cause ppaaxx to at-
tempt to recover from read errors forever. The default _l_i_m_i_t is a
small positive number of retries.
_W_a_r_n_i_n_g_: Using this option with NONE should be used with extreme
caution as ppaaxx may get stuck in an infinite loop on a very badly
flawed archive.
--GG _g_r_o_u_p
Select a file based on its _g_r_o_u_p name, or when starting with a ##, a
numeric gid. A '\' can be used to escape the ##. Multiple --GG op-
tions may be supplied and checking stops with the first match.
--HH Follow only command line symbolic links while performing a physical
file system traversal.
--LL Follow all symbolic links to perform a logical file system traver-
sal.
--TT _[_f_r_o_m___d_a_t_e_]_[_,_t_o___d_a_t_e_]_[_/_[_c_]_[_m_]_]
Allow files to be selected based on a file modification or inode
change time falling within a specified time range of _f_r_o_m___d_a_t_e to
_t_o___d_a_t_e (the dates are inclusive). If only a _f_r_o_m___d_a_t_e is sup-
plied, all files with a modification or inode change time equal to
or younger are selected. If only a _t_o___d_a_t_e is supplied, all files
with a modification or inode change time equal to or older will be
selected. When the _f_r_o_m___d_a_t_e is equal to the _t_o___d_a_t_e, only files
with a modification or inode change time of exactly that time will
be selected.
When ppaaxx is in the _w_r_i_t_e or _c_o_p_y 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 in-
ode 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 ppaaxx 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 yyyy is the last two digits of the year, the first mmmm is the
month (from 01 to 12), dddd is the day of the month (from 01 to 31),
hhhh is the hour of the day (from 00 to 23), the second mmmm is the
minute (from 00 to 59), and ssss is the seconds (from 00 to 59). The
minute field mmmm is required, while the other fields are optional
and must be added in the following order:
hhhh, dddd, mmmm, yyyy.
The ssss field may be added independently of the other fields. Time
ranges are relative to the current time, so
--TT _1_2_3_4_/_c_m
would select all files with a modification or inode change time of
12:34 PM today or later. Multiple --TT time range can be supplied
and checking stops with the first match.
--UU _u_s_e_r
Select a file based on its _u_s_e_r name, or when starting with a ##, a
numeric uid. A '\' can be used to escape the ##. Multiple --UU op-
tions may be supplied and checking stops with the first match.
--XX 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 de-
vice ID's.
--YY This option is the same as the --DD option, except that the inode
change time is checked using the pathname created after all the
file name modifications have completed.
--ZZ This option is the same as the --uu option, except that the modifica-
tion 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 ( --cc,
--ii, --nn, --ss, --uu, --vv, --DD, --GG, --TT, --UU, --YY, and --ZZ) interact as follows.
When extracting files during a _r_e_a_d operation, archive members are
`selected', based only on the user specified pattern operands as modified
by the --cc, --nn, --uu, --DD, --GG, --TT, --UU options. Then any --ss and --ii options
will modify in that order, the names of these selected files. Then the
--YY and --ZZ options will be applied based on the final pathname. Finally
the --vv option will write the names resulting from these modifications.
When archiving files during a _w_r_i_t_e operation, or copying files during a
_c_o_p_y operation, archive members are `selected', based only on the user
specified pathnames as modified by the --nn, --uu, --DD, --GG, --TT, and --UU options
(the --DD option only applies during a copy operation). Then any --ss and --ii
options will modify in that order, the names of these selected files.
Then during a _c_o_p_y operation the --YY and the --ZZ options will be applied
based on the final pathname. Finally the --vv option will write the names
resulting from these modifications.
When one or both of the --uu or --DD options are specified along with the --nn
option, a file is not considered selected unless it is newer than the
file to which it is compared.
EEXXAAMMPPLLEESS
The command:
pax -w -f /dev/rst0 .
copies the contents of the current directory to the device _/_d_e_v_/_r_s_t_0.
The command:
pax -r -v -f filename
gives the verbose table of contents for an archive stored in _f_i_l_e_n_a_m_e.
The following commands:
mkdir newdir
cd olddir
pax -rw . newdir
will copy the entire _o_l_d_d_i_r directory hierarchy to _n_e_w_d_i_r.
The command:
pax -r -s ',^//*usr//*,,' -f a.pax
reads the archive _a_._p_a_x, with all files rooted in ``/usr'' into the
archive extracted relative to the current directory.
The command:
pax -rw -i . dest_dir
can be used to interactively select the files to copy from the current
directory to _d_e_s_t___d_i_r.
The command:
pax -r -pe -U root -G bin -f a.pax
will extract all files from the archive _a_._p_a_x which are owned by _r_o_o_t
with group _b_i_n and will preserve all file permissions.
The command:
pax -r -w -v -Y -Z home /backup
will update (and list) only those files in the destination directory
_/_b_a_c_k_u_p which are older (less recent inode change or file modification
times) than files with the same name found in the source file tree _h_o_m_e.
SSTTAANNDDAARRDDSS
The ppaaxx utility is a superset of the IEEE Std1003.2 (``POSIX'') standard.
The options --BB, --DD, --EE, --GG, --HH, --TT, --UU, --YY, --ZZ, the archive formats
_b_c_p_i_o, _s_v_4_c_p_i_o, _s_v_4_c_r_c, _t_a_r, and the flawed archive handling during _l_i_s_t
and _r_e_a_d operations are extensions to the POSIX standard.
AAUUTTHHOORR
Keith Muller at the University of California, San Diego
EERRRROORRSS
ppaaxx will exit with one of the following values:
0 All files were processed successfully.
1 An error occurred.
Whenever ppaaxx 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 --pp 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, ppaaxx 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, ppaaxx 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, ppaaxx may have only partially created the archive which may violate
the specific archive format specification.
If while doing a _c_o_p_y, ppaaxx detects a file is about to overwrite itself,
the file is not copied, a diagnostic message is written to standard error
and when ppaaxx completes it will exit with a non-zero exit status.
4.4BSD May 31, 1993 9