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std::filesystem::file_size

From cppreference.com
 
 
 
Defined in header <filesystem>
(1) (since C++17)

If p does not exist, reports an error.

For a regular file p, returns the size determined as if by reading the st_size member of the structure obtained by POSIX stat (symlinks are followed)

The result of attempting to determine the size of a directory (as well as any other file that is not a regular file or a symlink) is implementation-defined.

The non-throwing overload returns returns -1 on errors.

Contents

[edit] Parameters

p - path to examine
ec - out-parameter for error reporting in the non-throwing overload

[edit] Return value

The size of the file, in bytes.

[edit] Exceptions

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 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 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.

[edit] Example

#include <iostream>
#include <fstream>
#include <filesystem>
namespace fs = std::filesystem;
int main()
{
    fs::path p = fs::current_path() / "example.bin";
    std::ofstream(p).put('a'); // create file of size 1
    std::cout << "File size = " << fs::file_size(p) << '\n';
    fs::remove(p);
 
    try {
        fs::file_size("/dev"); // attempt to get size of a directory
    } catch(fs::filesystem_error& e) {
        std::cout << e.what() << '\n';
    }        
}

Possible output:

File size = 1
boost::filesystem::file_size: Operation not permitted: "/dev"

[edit] See also

changes the size of a regular file by truncation or zero-fill
(function) [edit]
(C++17)
determines available free space on the file system
(function) [edit]
returns the size of the file to which the directory entry refers
(public member function of std::filesystem::directory_entry) [edit]