std::filesystem::exists

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 ) 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

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

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