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/C++std::filesystem::filesystem_error
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.
Inheritance diagram.
Member functions
| constructs the exception object (public member function) |
|
| replaces the exception object (public member function) |
|
| returns the paths that were involved in the operation that caused the error (public member function) |
|
| returns the explanatory string (public member function) |
Inherited from std::system_error
Member functions
| returns error code (public member function of std::system_error) |
|
|
[virtual] | returns an explanatory string (virtual public member function of std::system_error) |
Inherited from std::runtime_error
Inherited from std::exception
Member functions
|
[virtual] | destroys the exception object (virtual public member function of std::exception) |
|
[virtual] | returns an explanatory string (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
#include <system_error>
#include <filesystem>
#include <iostream>
int main()
{
const std::filesystem::path from{"/nonexistent1/a"}, to{"/nonexistent2/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 [/nonexistent1/a] [/nonexistent2/b] path1(): "/nonexistent1/a" path2(): "/nonexistent2/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
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