[GRASSGUI] Re: grassgui Digest, Vol 4, Issue 6

[Michael Barton]

Thanks again Glynn


On 6/10/07 6:34 AM, "grassgui-***@grass.itc.it"
<grassgui-***@grass.itc.it> wrote:

The file= option would be most useful for users directly accessing the
command.

An alternative is to add stdin= and stdout= pseudo-options to the
module's GUI dialog, so that the user can redirect stdin/stdout of any
command from/to a file. This can be done in addition to a file= option
for modules where it would be useful.

Within a GUI environment, I'd like to be able to send these (and some other
commands a set of rules stored in a variable, so that I don't have to save
them to a tmp file and do the equivalent of...

cat [file] | r.recode input=[map] output=[map]

I'd rather do the equivalent of ...

echo $rules > r.recode input=[map] output=[map]

I'm not sure if this is permitted now, nor how to do it in Python if it is.

Nevertheless, if there is a file= option for all these color/reclass/recode
modules it would at least be consistent and I can deal with it.

However: any module which is run from the GUI must behave in a
non-interactive manner regardless of which flags/options the user
selects. Having the module hang because the user chose a combination
of options which results in the module trying to read from stdin isn't
acceptable.

At least within a GUI setting this should be preventable.

Michael

You can probably eliminate hanging by simply closing stdin (or
redirecting it from /dev/null), although that may just result in a
different form of misbehaviour.

__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: [phone]
fax: [phone]
www: http://www.public.asu.edu/~cmbarton

[Glynn Clements]

Post by Michael Barton
The file= option would be most useful for users directly accessing the
command.

An alternative is to add stdin= and stdout= pseudo-options to the
module's GUI dialog, so that the user can redirect stdin/stdout of any
command from/to a file. This can be done in addition to a file= option
for modules where it would be useful.

Within a GUI environment, I'd like to be able to send these (and some other
commands a set of rules stored in a variable, so that I don't have to save
them to a tmp file and do the equivalent of...
cat [file] | r.recode input=[map] output=[map]
I'd rather do the equivalent of ...
echo $rules > r.recode input=[map] output=[map]

This is meaningless; the RHS of the ">" operator has to be a filename.

If you don't want to use a temporary file, use stdin, i.e.:

echo "$rules" | r.recode input=[map] output=[map]

The other alternative would be to pass the rules as an argument, e.g.:

r.recode input=[map] output=[map] rules="`echo $rules`"

However, a long list of rules could easily overflow the maximum length
of a command line (which may be as low as 1Kb on some platforms).

[Michael Barton]

Post by Glynn Clements
r.recode input=[map] output=[map] rules="`echo $rules`"
However, a long list of rules could easily overflow the maximum length
of a command line (which may be as low as 1Kb on some platforms).

If that is a potential problem, then the tempfile solution is easy enough,
especially if a rules=[file] could be added to r.reclass and r.recode
(already exists for v.reclass and r.colors)

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: [phone]
fax: [phone]
www: http://www.public.asu.edu/~cmbarton

[Glynn Clements]

Post by Michael Barton

Post by Glynn Clements
r.recode input=[map] output=[map] rules="`echo $rules`"
However, a long list of rules could easily overflow the maximum length
of a command line (which may be as low as 1Kb on some platforms).

If that is a potential problem, then the tempfile solution is easy enough,
especially if a rules=[file] could be added to r.reclass and r.recode
(already exists for v.reclass and r.colors)

If the GUI is explicitly calling r.recode (etc), using a pipe and
stdin is simpler than creating a tempfile.

An explicit file= option is useful primarily for the generic dialogs,
where the user cannot (currently) choose to redirect stdin from a file
(and even if that functionality is added, a specific file= option is
likely to be more intuitive).