14.8.2.3 :file

The header argument :file is used to specify an external file in which to save code block results. After code block evaluation an Org mode style [[file:]] link (see Link format) to the file will be inserted into the Org mode buffer. Some languages including R, gnuplot, dot, and ditaa provide special handling of the :file header argument automatically wrapping the code block body in the boilerplate code required to save output to the specified file. This is often useful for saving graphical output of a code block to the specified file.

The argument to :file should be either a string specifying the path to a file, or a list of two strings in which case the first element of the list should be the path to a file and the second a description for the link.