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PROGRAM:

NAME


cp — copy files

SYNOPSIS


cp [−Pfip] source_file target_file

cp [−Pfip] source_file... target

cp −R [−H|−L|−P] [−fip] source_file... target

DESCRIPTION


The first synopsis form is denoted by two operands, neither of which are existing files of
type directory. The cp utility shall copy the contents of source_file (or, if source_file
is a file of type symbolic link, the contents of the file referenced by source_file) to
the destination path named by target_file.

The second synopsis form is denoted by two or more operands where the −R option is not
specified and the first synopsis form is not applicable. It shall be an error if any
source_file is a file of type directory, if target does not exist, or if target does not
name a directory. The cp utility shall copy the contents of each source_file (or, if
source_file is a file of type symbolic link, the contents of the file referenced by
source_file) to the destination path named by the concatenation of target, a single
<slash> character if target did not end in a <slash>, and the last component of
source_file.

The third synopsis form is denoted by two or more operands where the −R option is
specified. The cp utility shall copy each file in the file hierarchy rooted in each
source_file to a destination path named as follows:

* If target exists and names an existing directory, the name of the corresponding
destination path for each file in the file hierarchy shall be the concatenation of
target, a single <slash> character if target did not end in a <slash>, and the
pathname of the file relative to the directory containing source_file.

* If target does not exist and two operands are specified, the name of the corresponding
destination path for source_file shall be target; the name of the corresponding
destination path for all other files in the file hierarchy shall be the concatenation
of target, a <slash> character, and the pathname of the file relative to source_file.

It shall be an error if target does not exist and more than two operands are specified, or
if target exists and does not name a directory.

In the following description, the term dest_file refers to the file named by the
destination path. The term source_file refers to the file that is being copied, whether
specified as an operand or a file in a file hierarchy rooted in a source_file operand. If
source_file is a file of type symbolic link:

* If the −R option was not specified, cp shall take actions based on the type and
contents of the file referenced by the symbolic link, and not by the symbolic link
itself, unless the −P option was specified.

* If the −R option was specified:

-- If none of the options −H, −L, nor −P were specified, it is unspecified which of
−H, −L, or −P will be used as a default.

-- If the −H option was specified, cp shall take actions based on the type and
contents of the file referenced by any symbolic link specified as a source_file
operand.

-- If the −L option was specified, cp shall take actions based on the type and
contents of the file referenced by any symbolic link specified as a source_file
operand or any symbolic links encountered during traversal of a file hierarchy.

-- If the −P option was specified, cp shall copy any symbolic link specified as a
source_file operand and any symbolic links encountered during traversal of a file
hierarchy, and shall not follow any symbolic links.

For each source_file, the following steps shall be taken:

1. If source_file references the same file as dest_file, cp may write a diagnostic
message to standard error; it shall do nothing more with source_file and shall go on
to any remaining files.

2. If source_file is of type directory, the following steps shall be taken:

a. If the −R option was not specified, cp shall write a diagnostic message to
standard error, do nothing more with source_file, and go on to any remaining
files.

b. If source_file was not specified as an operand and source_file is dot or dot-dot,
cp shall do nothing more with source_file and go on to any remaining files.

c. If dest_file exists and it is a file type not specified by the System Interfaces
volume of POSIX.1‐2008, the behavior is implementation-defined.

d. If dest_file exists and it is not of type directory, cp shall write a diagnostic
message to standard error, do nothing more with source_file or any files below
source_file in the file hierarchy, and go on to any remaining files.

e. If the directory dest_file does not exist, it shall be created with file
permission bits set to the same value as those of source_file, modified by the
file creation mask of the user if the −p option was not specified, and then
bitwise-inclusively OR'ed with S_IRWXU. If dest_file cannot be created, cp shall
write a diagnostic message to standard error, do nothing more with source_file,
and go on to any remaining files. It is unspecified if cp attempts to copy files
in the file hierarchy rooted in source_file.

f. The files in the directory source_file shall be copied to the directory dest_file,
taking the four steps (1 to 4) listed here with the files as source_files.

g. If dest_file was created, its file permission bits shall be changed (if necessary)
to be the same as those of source_file, modified by the file creation mask of the
user if the −p option was not specified.

h. The cp utility shall do nothing more with source_file and go on to any remaining
files.

3. If source_file is of type regular file, the following steps shall be taken:

a. The behavior is unspecified if dest_file exists and was written by a previous
step. Otherwise, if dest_file exists, the following steps shall be taken:

i. If the −i option is in effect, the cp utility shall write a prompt to the
standard error and read a line from the standard input. If the response is
not affirmative, cp shall do nothing more with source_file and go on to any
remaining files.

ii. A file descriptor for dest_file shall be obtained by performing actions
equivalent to the open() function defined in the System Interfaces volume of
POSIX.1‐2008 called using dest_file as the path argument, and the bitwise-
inclusive OR of O_WRONLY and O_TRUNC as the oflag argument.

iii. If the attempt to obtain a file descriptor fails and the −f option is in
effect, cp shall attempt to remove the file by performing actions equivalent
to the unlink() function defined in the System Interfaces volume of
POSIX.1‐2008 called using dest_file as the path argument. If this attempt
succeeds, cp shall continue with step 3b.

b. If dest_file does not exist, a file descriptor shall be obtained by performing
actions equivalent to the open() function defined in the System Interfaces volume
of POSIX.1‐2008 called using dest_file as the path argument, and the bitwise-
inclusive OR of O_WRONLY and O_CREAT as the oflag argument. The file permission
bits of source_file shall be the mode argument.

c. If the attempt to obtain a file descriptor fails, cp shall write a diagnostic
message to standard error, do nothing more with source_file, and go on to any
remaining files.

d. The contents of source_file shall be written to the file descriptor. Any write
errors shall cause cp to write a diagnostic message to standard error and continue
to step 3e.

e. The file descriptor shall be closed.

f. The cp utility shall do nothing more with source_file. If a write error occurred
in step 3d, it is unspecified if cp continues with any remaining files. If no
write error occurred in step 3d, cp shall go on to any remaining files.

4. Otherwise, the −R option was specified, and the following steps shall be taken:

a. The dest_file shall be created with the same file type as source_file.

b. If source_file is a file of type FIFO, the file permission bits shall be the same
as those of source_file, modified by the file creation mask of the user if the −p
option was not specified. Otherwise, the permissions, owner ID, and group ID of
dest_file are implementation-defined.

If this creation fails for any reason, cp shall write a diagnostic message to
standard error, do nothing more with source_file, and go on to any remaining
files.

c. If source_file is a file of type symbolic link, and the options require the
symbolic link itself to be acted upon, the pathname contained in dest_file shall
be the same as the pathname contained in source_file.

If this fails for any reason, cp shall write a diagnostic message to standard
error, do nothing more with source_file, and go on to any remaining files.

If the implementation provides additional or alternate access control mechanisms (see the
Base Definitions volume of POSIX.1‐2008, Section 4.4, File Access Permissions), their
effect on copies of files is implementation-defined.

OPTIONS


The cp utility shall conform to the Base Definitions volume of POSIX.1‐2008, Section 12.2,
Utility Syntax Guidelines.

The following options shall be supported:

−f If a file descriptor for a destination file cannot be obtained, as described in
step 3.a.ii., attempt to unlink the destination file and proceed.

−H Take actions based on the type and contents of the file referenced by any
symbolic link specified as a source_file operand.

−i Write a prompt to standard error before copying to any existing non-directory
destination file. If the response from the standard input is affirmative, the
copy shall be attempted; otherwise, it shall not.

−L Take actions based on the type and contents of the file referenced by any
symbolic link specified as a source_file operand or any symbolic links
encountered during traversal of a file hierarchy.

−P Take actions on any symbolic link specified as a source_file operand or any
symbolic link encountered during traversal of a file hierarchy.

−p Duplicate the following characteristics of each source file in the corresponding
destination file:

1. The time of last data modification and time of last access. If this
duplication fails for any reason, cp shall write a diagnostic message to
standard error.

2. The user ID and group ID. If this duplication fails for any reason, it is
unspecified whether cp writes a diagnostic message to standard error.

3. The file permission bits and the S_ISUID and S_ISGID bits. Other,
implementation-defined, bits may be duplicated as well. If this duplication
fails for any reason, cp shall write a diagnostic message to standard error.

If the user ID or the group ID cannot be duplicated, the file permission bits
S_ISUID and S_ISGID shall be cleared. If these bits are present in the source
file but are not duplicated in the destination file, it is unspecified whether
cp writes a diagnostic message to standard error.

The order in which the preceding characteristics are duplicated is unspecified.
The dest_file shall not be deleted if these characteristics cannot be preserved.

−R Copy file hierarchies.

Specifying more than one of the mutually-exclusive options −H, −L, and −P shall not be
considered an error. The last option specified shall determine the behavior of the
utility.

OPERANDS


The following operands shall be supported:

source_file
A pathname of a file to be copied. If a source_file operand is '−', it shall
refer to a file named ; implementations shall not treat it as meaning standard
input.

target_file
A pathname of an existing or nonexistent file, used for the output when a single
file is copied. If a target_file operand is '−', it shall refer to a file named
; implementations shall not treat it as meaning standard output.

target A pathname of a directory to contain the copied files.

STDIN


The standard input shall be used to read an input line in response to each prompt
specified in the STDERR section. Otherwise, the standard input shall not be used.

INPUT FILES


The input files specified as operands may be of any file type.

ENVIRONMENT VARIABLES


The following environment variables shall affect the execution of cp:

LANG Provide a default value for the internationalization variables that are unset or
null. (See the Base Definitions volume of POSIX.1‐2008, Section 8.2,
Internationalization Variables for the precedence of internationalization
variables used to determine the values of locale categories.)

LC_ALL If set to a non-empty string value, override the values of all the other
internationalization variables.

LC_COLLATE
Determine the locale for the behavior of ranges, equivalence classes, and multi-
character collating elements used in the extended regular expression defined for
the yesexpr locale keyword in the LC_MESSAGES category.

LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data
as characters (for example, single-byte as opposed to multi-byte characters in
arguments and input files) and the behavior of character classes used in the
extended regular expression defined for the yesexpr locale keyword in the
LC_MESSAGES category.

LC_MESSAGES
Determine the locale used to process affirmative responses, and the locale used
to affect the format and contents of diagnostic messages and prompts written to
standard error.

NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES.

ASYNCHRONOUS EVENTS


Default.

STDOUT


Not used.

STDERR


A prompt shall be written to standard error under the conditions specified in the
DESCRIPTION section. The prompt shall contain the destination pathname, but its format is
otherwise unspecified. Otherwise, the standard error shall be used only for diagnostic
messages.

OUTPUT FILES


The output files may be of any type.

EXTENDED DESCRIPTION


None.

EXIT STATUS


The following exit values shall be returned:

0 All files were copied successfully.

>0 An error occurred.

CONSEQUENCES OF ERRORS


If cp is prematurely terminated by a signal or error, files or file hierarchies may be
only partially copied and files and directories may have incorrect permissions or access
and modification times.

The following sections are informative.

APPLICATION USAGE


The set-user-ID and set-group-ID bits are explicitly cleared when files are created. This
is to prevent users from creating programs that are set-user-ID or set-group-ID to them
when copying files or to make set-user-ID or set-group-ID files accessible to new groups
of users. For example, if a file is set-user-ID and the copy has a different group ID
than the source, a new group of users has execute permission to a set-user-ID program than
did previously. In particular, this is a problem for superusers copying users' trees.

EXAMPLES


None.

RATIONALE


The −i option exists on BSD systems, giving applications and users a way to avoid
accidentally removing files when copying. Although the 4.3 BSD version does not prompt if
the standard input is not a terminal, the standard developers decided that use of −i is a
request for interaction, so when the destination path exists, the utility takes
instructions from whatever responds on standard input.

The exact format of the interactive prompts is unspecified. Only the general nature of the
contents of prompts are specified because implementations may desire more descriptive
prompts than those used on historical implementations. Therefore, an application using the
−i option relies on the system to provide the most suitable dialog directly with the user,
based on the behavior specified.

The −p option is historical practice on BSD systems, duplicating the time of last data
modification and time of last access. This volume of POSIX.1‐2008 extends it to preserve
the user and group IDs, as well as the file permissions. This requirement has obvious
problems in that the directories are almost certainly modified after being copied. This
volume of POSIX.1‐2008 requires that the modification times be preserved. The statement
that the order in which the characteristics are duplicated is unspecified is to permit
implementations to provide the maximum amount of security for the user. Implementations
should take into account the obvious security issues involved in setting the owner, group,
and mode in the wrong order or creating files with an owner, group, or mode different from
the final value.

It is unspecified whether cp writes diagnostic messages when the user and group IDs cannot
be set due to the widespread practice of users using −p to duplicate some portion of the
file characteristics, indifferent to the duplication of others. Historic implementations
only write diagnostic messages on errors other than [EPERM].

Earlier versions of this standard included support for the −r option to copy file
hierarchies. The −r option is historical practice on BSD and BSD-derived systems. This
option is no longer specified by POSIX.1‐2008 but may be present in some implementations.
The −R option was added as a close synonym to the −r option, selected for consistency with
all other options in this volume of POSIX.1‐2008 that do recursive directory descent.

The difference between −R and the removed −r option is in the treatment by cp of file
types other than regular and directory. It was implementation-defined how the option
treated special files to allow both historical implementations and those that chose to
support −r with the same abilities as −R defined by this volume of POSIX.1‐2008. The
original −r flag, for historic reasons, did not handle special files any differently from
regular files, but always read the file and copied its contents. This had obvious problems
in the presence of special file types; for example, character devices, FIFOs, and sockets.

When a failure occurs during the copying of a file hierarchy, cp is required to attempt to
copy files that are on the same level in the hierarchy or above the file where the failure
occurred. It is unspecified if cp shall attempt to copy files below the file where the
failure occurred (which cannot succeed in any case).

Permissions, owners, and groups of created special file types have been deliberately left
as implementation-defined. This is to allow systems to satisfy special requirements (for
example, allowing users to create character special devices, but requiring them to be
owned by a certain group). In general, it is strongly suggested that the permissions,
owner, and group be the same as if the user had run the historical mknod, ln, or other
utility to create the file. It is also probable that additional privileges are required to
create block, character, or other implementation-defined special file types.

Additionally, the −p option explicitly requires that all set-user-ID and set-group-ID
permissions be discarded if any of the owner or group IDs cannot be set. This is to keep
users from unintentionally giving away special privilege when copying programs.

When creating regular files, historical versions of cp use the mode of the source file as
modified by the file mode creation mask. Other choices would have been to use the mode of
the source file unmodified by the creation mask or to use the same mode as would be given
to a new file created by the user (plus the execution bits of the source file) and then
modify it by the file mode creation mask. In the absence of any strong reason to change
historic practice, it was in large part retained.

When creating directories, historical versions of cp use the mode of the source directory,
plus read, write, and search bits for the owner, as modified by the file mode creation
mask. This is done so that cp can copy trees where the user has read permission, but the
owner does not. A side-effect is that if the file creation mask denies the owner
permissions, cp fails. Also, once the copy is done, historical versions of cp set the
permissions on the created directory to be the same as the source directory, unmodified by
the file creation mask.

This behavior has been modified so that cp is always able to create the contents of the
directory, regardless of the file creation mask. After the copy is done, the permissions
are set to be the same as the source directory, as modified by the file creation mask.
This latter change from historical behavior is to prevent users from accidentally creating
directories with permissions beyond those they would normally set and for consistency with
the behavior of cp in creating files.

It is not a requirement that cp detect attempts to copy a file to itself; however,
implementations are strongly encouraged to do so. Historical implementations have detected
the attempt in most cases.

There are two methods of copying subtrees in this volume of POSIX.1‐2008. The other method
is described as part of the pax utility (see pax). Both methods are historical practice.
The cp utility provides a simpler, more intuitive interface, while pax offers a finer
granularity of control. Each provides additional functionality to the other; in
particular, pax maintains the hard-link structure of the hierarchy, while cp does not. It
is the intention of the standard developers that the results be similar (using appropriate
option combinations in both utilities). The results are not required to be identical;
there seemed insufficient gain to applications to balance the difficulty of
implementations having to guarantee that the results would be exactly identical.

The wording allowing cp to copy a directory to implementation-defined file types not
specified by the System Interfaces volume of POSIX.1‐2008 is provided so that
implementations supporting symbolic links are not required to prohibit copying directories
to symbolic links. Other extensions to the System Interfaces volume of POSIX.1‐2008 file
types may need to use this loophole as well.

FUTURE DIRECTIONS


None.

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