NAME¶

std::experimental::filesystem::copy_file - std::experimental::filesystem::copy_file

Synopsis¶

Defined in header <experimental/filesystem>
bool copy_file( const path& from, const path& to );
bool copy_file( const path& from, const path& to, error_code& ec (1) (filesystem TS)
);
bool copy_file( const path& from, const path& to, copy_options
options ); (2) (filesystem TS)
bool copy_file( const path& from, const path& to, copy_options
options, error_code& ec );

1) The default, equivalent to (2) with copy_options::none used as options
2) Copies a single file from from to to, using the copy options indicated by
options. The behavior is undefined if there is more than one option in any of the
copy_options option group present in options (even in the groups not relevant to
copy_file)

* If the destination file does not exist,

* copies the contents and the attributes of the file to which from
resolves to the file to which to resolves (symlinks are followed)

* Otherwise, if the destination file already exists...

* If to and from are the same as determined by equivalent(from, to),
report an error
* Otherwise, if none of the copy_file control options are set in options,
report an error
* Otherwise, if copy_options::skip_existing is set in options, do nothing
* Otherwise, if copy_options::overwrite_existing is set in options, copy
the contents and the attributes of the file to which from resolves to
the file to which to resolves
* Otherwise, if copy_options::update_existing is set in options, only
copy the file if from is newer than to, as defined by last_write_time()

The non-throwing overloads return false if an error occurs.

Parameters¶

from - path to the source file
to - path to the target file
ec - out-parameter for error reporting in the non-throwing overload

Return value¶

true if the file was copied, false otherwise.

Exceptions¶

The overload that does not take a error_code& parameter throws filesystem_error on
underlying OS API errors, constructed with from as the first argument, to as the
second argument, and the OS error code as the error code argument. std::bad_alloc
may be thrown if memory allocation fails. The overload taking a error_code&
parameter sets it to the OS API error code if an OS API call fails, and executes
ec.clear() if no errors occur. This overload has
noexcept specification:
noexcept

Notes¶

The functions involve at most one direct or indirect call to status(to) (used both
to determine if the file exists, and, for copy_options::update_existing option, its
last write time)

Error is reported when copy_file is used to copy a directory: use copy for that.

copy_file follows symlinks: use copy_symlink or copy with
copy_options::copy_symlinks for that.

Examples¶

// Run this code

#include <fstream>
#include <iostream>
#include <experimental/filesystem>
namespace fs = std::experimental::filesystem;

int main()
{
fs::create_directory("sandbox");
std::ofstream("sandbox/file1.txt").put('a');

fs::copy_file("sandbox/file1.txt", "sandbox/file2.txt");

// now there are two files in sandbox:
std::cout << "file1.txt holds : "
<< std::ifstream("sandbox/file1.txt").rdbuf() << '\n';
std::cout << "file2.txt holds : "
<< std::ifstream("sandbox/file2.txt").rdbuf() << '\n';

// fail to copy directory
fs::create_directory("sandbox/abc");
try {
fs::copy_file("sandbox/abc", "sandbox/def");
} catch(fs::filesystem_error& e) {
std::cout << "Could not copy sandbox/abc: " << e.what() << '\n';
}
fs::remove_all("sandbox");
}

Possible output:¶

file1.txt holds : a
file2.txt holds : a
Could not copy sandbox/abc: copy_file: Is a directory: "sandbox/abc", "sandbox/def"

See also¶

copy_options specifies semantics of copy operations
(enum)
copy_symlink copies a symbolic link
(function)
copy copies files or directories
(function)