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Showing content from https://en.cppreference.com/w/cpp/language/../algorithm/../symbol_index/../filesystem/exists.html below:

std::filesystem::exists - cppreference.com

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)

status(p, ec)

(symlinks are followed), respectively. Returns

exists(s)

. The non-throwing overload calls

ec.clear()

status_known(s)

[edit] Parameters s - file status to check p - path to examine ec - out-parameter for error reporting in the non-throwing overload [edit] Return value

true if the given path or file status corresponds to an existing file or directory, false otherwise.

[edit] 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).

[edit] 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()).

[edit] Example

#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

[edit] See also determines file attributes
determines file attributes, checking the symlink target
(function) [edit] represents file type and permissions
(class) [edit] checks whether directory entry refers to existing file system object
(public member function of std::filesystem::directory_entry) [edit]

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