Routing ppm output to a file

C Anderson writes:

  Has anyone used the p.map or an equivalent to output a ppm file
to a file rather than to a tty port or a display monitor. We would like
to be able to use on-site software to convert this file to other formats.

P.map only writes to the monitor if and while you have selected the
`preview' driver (p.select preview); if you select the `ppm' driver a
file is created.

Martijn van Leusen