[fs.op.file.size]

[fs.op.file.size]

31 Input/output library [input.output]

31.12 File systems [filesystems]

31.12.13 Filesystem operation functions [fs.op.funcs]

31.12.13.15 File size [fs.op.file.size]

uintmax_t filesystem::file_size(const path& p); uintmax_t filesystem::file_size(const path& p, error_code& ec) noexcept;

Returns:

If is_regular_file(p), the size in bytes of the file p resolves to, determined as if by the value of the POSIX stat class member st_size obtained as if by POSIX stat .
Otherwise, the result is implementation-defined.

The signature with argument ec returns static_cast<uintmax_t>(-1) if an error occurs.