std::filesystem::exists

 

C++

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Technical specifications

Symbols index

External libraries

 

Filesystem library

Classes
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator      filesystem::file_status	filesystem::space_info filesystem::file_type filesystem::perms filesystem::perm_options filesystem::copy_options filesystem::directory_options filesystem::file_time_type
Functions
filesystem::absolute filesystem::canonicalfilesystem::weakly_canonical filesystem::relativefilesystem::proximate filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path	filesystem::exists filesystem::equivalent filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status filesystem::temp_directory_path
File types
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

 

Defined in header <filesystem>
bool exists( std::filesystem::file_status s ) noexcept;	(1)	(since C++17)
bool exists( const std::filesystem::path& p );	(2)	(since C++17)
bool exists( const std::filesystem::path& p, std::error_code& ec ) noexcept;	(3)	(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.

2,3) 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

Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

2) Throws std::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.

3) Sets a std::error_code& parameter to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur.

No filesystem exception is thrown if object does not exist (use return value).

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 <filesystem>
#include <fstream>
#include <iostream>
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

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