Std::experimental::filesystem::exists (3) Linux Manual Page

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 a 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 a 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 <iostream>

#include <fstream>

#include <cstdint>

#include <experimental/filesystem>

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

std::experimental::filesystem::exists (3) Linux Manual Page