std::filesystem::filesystem_error
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<cpp |filesystem
C++
filesystem_error
Defined in header <filesystem> | ||
class filesystem_error; | (since C++17) | |
The classstd::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
Contents |
[edit]Member functions
| constructs the exception object (public member function)[edit] | |
| replaces the exception object (public member function)[edit] | |
| returns the paths that were involved in the operation that caused the error (public member function)[edit] | |
| returns the explanatory string (public member function)[edit] |
Inherited fromstd::system_error
Member functions
| returns error code (public member function of std::system_error)[edit] | |
[virtual] | returns an explanatory string (virtual public member function of std::system_error)[edit] |
Inherited fromstd::runtime_error
Inherited fromstd::exception
Member functions
[virtual] | destroys the exception object (virtual public member function of std::exception)[edit] |
[virtual] | returns an explanatory string (virtual public member function of std::exception)[edit] |
[edit]Notes
In order to ensure that copy functions offilesystem_error are noexcept, typical implementations store an object holding the return value ofwhat() and twostd::filesystem::path objects referenced bypath1() andpath2() respectively in a separately-allocated reference-counted storage.
Currently theMS STL implementation is non-conforming: objects mentioned above are stored directly in thefilesystem object, which makes the copy functions not noexcept.
[edit]Example
Run this code
#include <filesystem>#include <iostream>#include <system_error> int main(){conststd::filesystem::path from{"/none1/a"}, to{"/none2/b"}; try{std::filesystem::copy_file(from, to);// throws: files do not exist}catch(std::filesystem::filesystem_errorconst& 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 equivalentsstd::error_code ec;std::filesystem::copy_file(from, to, ec);// does not throwstd::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(): 2code().message(): No such file or directorycode().category(): generic Non-throwing form sets error_code: No such file or directory
