std::filesystem::exists
From cppreference.com
< cpp | filesystem
Defined in header <filesystem>
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bool exists( std::filesystem::file_status s ) noexcept; |
(1) | (since C++17) |
bool exists( const std::filesystem::path& p ); bool exists( const std::filesystem::path& p, std::error_code& ec ) noexcept; |
(2) | (since C++17) |
Checks if the given file status or path corresponds to an existing file or directory.
1) Equivalent to status_known(s) && s.type() != file_type::not_found.
2) Let
s
be a std::filesystem::file_status determined as if by status(p) or status(p, ec) (symlinks are followed), respectively. Returns exists(s). The non-throwing overload calls ec.clear() if status_known(s).Parameters
s | - | file status to check |
p | - | path to examine |
ec | - | out-parameter for error reporting in the non-throwing overload |
Return value
true if the given path or file status corresponds to an existing file or directory, false otherwise.
Exceptions
2) The overload that does not take a std::error_code& parameter throws filesystem_error on underlying OS API errors, constructed with
p
as the first path argument and the OS error code as the error code argument. The overload taking a std::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. Any overload not marked noexcept
may throw std::bad_alloc if memory allocation fails.Notes
The information provided by this function is usually also provided as a byproduct of directory iteration. During directory iteration, calling exists(*iterator)
is less efficient than exists(iterator->status())
Example
This section is incomplete Reason: switch to directory_entry::exists |
Run this code
#include <iostream> #include <fstream> #include <cstdint> #include <filesystem> namespace fs = std::filesystem; void demo_exists(const fs::path& p, fs::file_status s = fs::file_status{}) { std::cout << p; if(fs::status_known(s) ? fs::exists(s) : fs::exists(p)) std::cout << " exists\n"; else std::cout << " does not exist\n"; } int main() { fs::create_directory("sandbox"); std::ofstream("sandbox/file"); // create regular file fs::create_symlink("non-existing", "sandbox/symlink"); demo_exists("sandbox"); for(auto it = fs::directory_iterator("sandbox"); it != fs::directory_iterator(); ++it) demo_exists(*it, it->status()); // use cached status from directory entry fs::remove_all("sandbox"); }
Output:
"sandbox" exists "sandbox/file" exists "sandbox/symlink" does not exist
See also
(C++17)(C++17) |
determines file attributes determines file attributes, checking the symlink target (function) |
(C++17) |
represents file type and permissions (class) |
checks whether directory entry refers to existing file system object (public member function of std::filesystem::directory_entry ) |