std::filesystem::resize_file - cppreference.com (original) (raw)
| Defined in header | ||
|---|---|---|
| void resize_file( const std::filesystem::path& p, std::uintmax_t new_size ); | (1) | (since C++17) |
| void resize_file( const std::filesystem::path& p, std::uintmax_t new_size, std::error_code& ec ) noexcept; | (2) | (since C++17) |
Changes the size of the regular file named by p as if by POSIX truncate: if the file size was previously larger than new_size, the remainder of the file is discarded. If the file was previously smaller than new_size, the file size is increased and the new area appears as if zero-filled.
[edit] Parameters
| p | - | path to resize |
|---|---|---|
| new_size | - | size that the file will now have |
| ec | - | out-parameter for error reporting in the non-throwing overload |
[edit] Return value
(none)
[edit] Exceptions
Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.
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.
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.
[edit] Notes
On systems that support sparse files, increasing the file size does not increase the space it occupies on the file system: space allocation takes place only when non-zero bytes are written to the file.
[edit] Example
Demonstrates the effect creating a sparse file has on the free space.
Possible output:
File size: 1 Free space: 42,954,108,928 File size: 65,536 Free space: 42,954,108,928
[edit] See also
| | returns the size of a file (function) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | | determines available free space on the file system (function) [edit] |