NAME¶

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

Synopsis¶

Defined in header <experimental/filesystem>
bool exists( file_status s ) (1) (filesystem TS)
bool exists( const path& p ); (2) (filesystem TS)
bool exists( const path& p, error_code& ec )

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) Equivalent to exists(status(p)) or exists(status(p, ec)) (symlinks are followed).
The non-throwing overload returns false if an error occurs.

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¶

1)
noexcept specification:
noexcept

2) The overload that does not take an error_code& parameter throws filesystem_error
on underlying OS API errors, constructed with p as the first argument and the OS
error code as the error code argument. std::bad_alloc may be thrown if memory
allocation fails. The overload taking an 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. This
overload has
noexcept specification:
noexcept

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 <cstdint>
#include <experimental/filesystem>
#include <fstream>
#include <iostream>
namespace fs = std::experimental::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¶

status determines file attributes
symlink_status determines file attributes, checking the symlink target
(function)
file_status represents file type and permissions
(class)
cached status of the file designated by this directory entry
status cached symlink_status of the file designated by this directory entry
symlink_status (public member function of
std::experimental::filesystem::directory_entry)

Categories:¶

* Noindexed pages
* unconditionally noexcept

Hidden categories:¶

* Pages with unreviewed unconditional noexcept template
* Pages with unreviewed noexcept template