/// Truncate a file to a specified length.
///
/// # Examples
///
/// ```
/// let path = "/tmp/nc-truncate";
/// let ret = unsafe { nc::openat(nc::AT_FDCWD, path, nc::O_WRONLY | nc::O_CREAT, 0o644) };
/// assert!(ret.is_ok());
/// let fd = ret.unwrap();
/// let ret = unsafe { nc::close(fd) };
/// assert!(ret.is_ok());
/// let ret = unsafe { nc::truncate(path, 64 * 1024) };
/// assert!(ret.is_ok());
/// let ret = unsafe { nc::unlinkat(nc::AT_FDCWD, path, 0) };
/// assert!(ret.is_ok());
/// ```
pub unsafe fn truncate<P: AsRef<Path>>(filename: P, length: off_t) -> Result<(), Errno> {
    let filename = CString::new(filename.as_ref());
    let filename_ptr = filename.as_ptr() as usize;
    let length = length as usize;
    unsafe { syscall2(SYS_TRUNCATE, filename_ptr, length).map(drop) }
}
