[GRASS-user] r.mapcalc in ssh session

[Glynn Clements]

Hufkens Koen wrote:

> this weekend I ssh'd in computer to let some processes run in the
> background so I have my results tommorow.
> 
> However my script crashes on a strange error related to r.mapcalc. I
> tried some r.mapcalc commands within the ssh'd GRASS session and I get
> the same error.
> 
> for example:
> 
> r.mapcalc amap=pnm bmap=pbl4 formula=A*B outfile=test --overwrite
> syntax error, unexpected NAME, expecting $end
> Parse error

The above syntax is valid for the r.mapcalculator script which is used
by gis.m, but not for r.mapcalc itself. You need to use either:

	GRASS_OVERWRITE=1 r.mapcalc 'test = pnm*pbl4'
or:
	r.mapcalculator amap=pnm bmap=pbl4 formula=A*B outfile=test --overwrite

In 6.4, r.mapcalc doesn't use the standard command-line parser, which
is part of the reason why r.mapcalculator exists and is used by gis.m.

In 7.0, r.mapcalc uses the command-line parser. This means that it
supports --help, --overwrite, --ui etc, but it also means that you
either have to specify the option name explicitly:

	r.mapcalc expression='test=pnm*pbl4'

or at least provide the expression as a single argument, formattted so
that it doesn't get mistaken for an option by ensuring that there is a
space before the first = sign.

This will work in 7.0:

	r.mapcalc expression=test=pnm*pbl4

This will work in both 7.0 and older versions:

	r.mapcalc 'test = pnm*pbl4'

This won't work in 7.0:

	r.mapcalc test=pnm*pbl4

(it will complain that r.mapcalc doesn't have an option named test=).

Nor will this:

	r.mapcalc test = pnm*pbl4

(expressions can't be split over multiple arguments).

Also, feeding the expression via stdin will work in all versions,
e.g.:

	echo "test = pnm*pbl4" | r.mapcalc
or:
	r.mapcalc <<EOF
	test = pnm*pbl4
	EOF

-- 
Glynn Clements <glynn at gclements.plus.com>