table of contents
std::filesystem::filesystem_error(3) | C++ Standard Libary | std::filesystem::filesystem_error(3) |
NAME¶
std::filesystem::filesystem_error - std::filesystem::filesystem_error
Synopsis¶
Defined in header <filesystem>
class filesystem_error; (since C++17)
The class std::filesystem::filesystem_error defines an exception object that
is
thrown on failure by the throwing overloads of the functions in the
filesystem
library.
std-filesystem-filesystem error-inheritance.svg
Inheritance diagram
Member functions¶
constructor constructs the exception object
(public member function)
operator= replaces the exception object
(public member function)
path1 returns the paths that were involved in the operation that caused the
path2 error
(public member function)
what returns the explanatory string
(public member function)
Inherited from std::system_error
Member functions¶
code returns error code
(public member function of std::system_error)
what returns an explanatory string
[virtual] (virtual public member function of
std::system_error)
Inherited from std::runtime_error
Inherited from std::exception
Member functions¶
destructor destroys the exception object
[virtual] (virtual public member function of std::exception)
what returns an explanatory string
[virtual] (virtual public member function of
std::exception)
Notes¶
In order to ensure that copy functions of filesystem_error are
noexcept, typical
implementations store an object holding the return value of what() and two
std::filesystem::path objects referenced by path1() and path2() respectively
in a
separately-allocated reference-counted storage.
Currently the MS STL implementation is non-conforming: objects mentioned
above are
stored directly in the filesystem object, which makes the copy functions not
noexcept.
Example¶
// Run this code
#include <filesystem>
#include <iostream>
#include <system_error>
int main()
{
const std::filesystem::path from{"/none1/a"},
to{"/none2/b"};
try
{
std::filesystem::copy_file(from, to); // throws: files do not exist
}
catch (std::filesystem::filesystem_error const& ex)
{
std::cout << "what(): " << ex.what() << '\n'
<< "path1(): " << ex.path1() << '\n'
<< "path2(): " << ex.path2() << '\n'
<< "code().value(): " << ex.code().value() <<
'\n'
<< "code().message(): " << ex.code().message() <<
'\n'
<< "code().category(): " << ex.code().category().name()
<< '\n';
}
// All functions have non-throwing equivalents
std::error_code ec;
std::filesystem::copy_file(from, to, ec); // does not throw
std::cout << "\nNon-throwing form sets error_code: " <<
ec.message() << '\n';
}
Possible output:¶
what(): filesystem error: cannot copy file: No such file or
directory [/none1/a] [/none2/b]
path1(): "/none1/a"
path2(): "/none2/b"
code().value(): 2
code().message(): No such file or directory
code().category(): generic
Non-throwing form sets error_code: No such file or directory
2024.06.10 | http://cppreference.com |