The **-:** option
^^^^^^^^^^^^^^^^^

**Syntax**

**-:**\ [**i**\|\ **o**]
    Swap 1st and 2nd column on input and/or output.

**Description**
The **-:** option swaps the 1st and 2nd column on input and output [default is no swapping]. Append **i** to select
input only or **o** to select output only [default affects both]. This option is typically used to handle (latitude,
longitude) files; see also :ref:`reference/options:Input columns selection: The **-i** option`. Note that command line
arguments that may take geographic coordinates (e.g., **-R**) *always* expect longitude before latitude. Also,
geographical grids are expected to have the longitude as first (minor) dimension.
