NAME¶

std::filesystem::exists - std::filesystem::exists

Synopsis¶

Defined in header <filesystem>
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 ) (2) (since C++17)
noexcept;

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::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¶

// 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()
{
const fs::path sandbox{"sandbox"};
fs::create_directory(sandbox);
std::ofstream{sandbox/"file"}; // create regular file
fs::create_symlink("non-existing", sandbox/"symlink");

demo_exists(sandbox);

for (const auto& entry : fs::directory_iterator(sandbox))
demo_exists(entry, entry.status()); // use cached status from directory entry

fs::remove_all(sandbox);
}

Output:¶

"sandbox" exists
"sandbox/symlink" does not exist
"sandbox/file" exists

See also¶

status determines file attributes
symlink_status determines file attributes, checking the symlink target
(C++17) (function)
(C++17)
file_status represents file type and permissions
(C++17) (class)
exists checks whether directory entry refers to existing file system object
(public member function of std::filesystem::directory_entry)