[GRASS-user] Call Grass modules from C++ code

GRASS GRASS user
1

Hi,

I'm implementing a model in C++ and I need to call some Grass modules from my code.

Which is the best way to do it? Are there APIs that allow me to use the modules as a library?

Thanks!

Matteo

2

see programmers manual[1]

http://grass.osgeo.org/programming7/

···

On Fri, Feb 15, 2013 at 7:54 PM, matteo poletti <pollo1_91@yahoo.it> wrote:

Hi,

I’m implementing a model in C++ and I need to call some Grass modules from my code.

Which is the best way to do it? Are there APIs that allow me to use the modules as a library?

Thanks!

Matteo

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–

Regards,
Rashad

3

On Fri, Feb 15, 2013 at 5:22 PM, Rashad M <mohammedrashadkm@gmail.com> wrote:

see programmers manual[1]

http://grass.osgeo.org/programming7/

On Fri, Feb 15, 2013 at 7:54 PM, matteo poletti <pollo1_91@yahoo.it> wrote:

Hi,

I'm implementing a model in C++ and I need to call some Grass modules from
my code.

Which is the best way to do it? Are there APIs that allow me to use the
modules as a library?

See also here (the page should be expanded):

http://grasswiki.osgeo.org/wiki/GRASS_and_C++

Markus

4

Da: Rashad M <mohammedrashadkm@gmail.com>

see programmers manual[1]
http://grass.osgeo.org/programming7/

Thanks
for your answer. I've seen the programmer's manual, but it seems to me
that it presents operations at a lower level than the one that I need.

For example if I want to call the module v.in.ogr from my code, what should I do? Maybe I'm missing something...

Thank you for your help!
Matteo

5

Da: Markus Neteler <neteler@osgeo.org>

See also here (the page should be expanded):
http://grasswiki.osgeo.org/wiki/GRASS_and_C++

Ok, I have understood that I need to put the keyword "extern". But I'm still confused about how to call other Grass module.

I've tried to see the examples linked in the wiki but it's a little bit difficult to understand how they work. Can you please suggest me a file where there is an example of calling another module?

Thank you for your help!
Matteo

6

matteo wrote:

Ok, I have understood that I need to put the keyword
"extern". But I'm still confused about how to call other
Grass module.

I've tried to see the examples linked in the wiki but it's a
little bit difficult to understand how they work. Can you
please suggest me a file where there is an example of
calling another module?

have a look at the functions in lib/gis/spawn.c.

there is also the less portable G_system() to look at in grass6.

you might look at raster/r.topmodel/misc.c in trunk for an example.

Hamish

7

Da: Hamish <hamish_b@yahoo.com>

have a look at the functions in lib/gis/spawn.c.

Ok, so if I got it right I need to do a sys call exec. What do you usually do for reading the module's output?

I suppose that, doing the things this way, I'll need to run my program inside a grass shell to have it working.

Do I need the "extern" keyword in this case? I guess not since I'm doing a sys call.

Maybe I've misunderstood the example...
Thanks!
Matteo

8

On 16 February 2013 00:42, matteo poletti <pollo1_91@yahoo.it> wrote:

Da: Hamish <hamish_b@yahoo.com>

have a look at the functions in lib/gis/spawn.c.

Ok, so if I got it right I need to do a sys call exec. What do you usually do for reading the module's output?

I hope this will help:

http://stackoverflow.com/questions/478898/how-to-execute-a-command-and-get-output-of-command-within-c

If you are using some framework such as Qt, you can use the way used
in this framework.

I suppose that, doing the things this way, I'll need to run my program inside a grass shell to have it working.

Yes, you always need to run your program (which uses lib or modules)
in grass session. Your program is in fact a grass module. However,
there is an alternative -- to set up some environment variables (most
recently discussed in thread "Bash aliases in GRASS").

http://grasswiki.osgeo.org/wiki/Working_with_GRASS_without_starting_it_explicitly

Do I need the "extern" keyword in this case? I guess not since I'm doing a sys call.

Exactly, "extern" is necessary to properly include function declarations.

Best,
Vaclav

BTW, I would ask this question on grass-dev. For me, it is more
developer than user question because of C++.

Maybe I've misunderstood the example...
Thanks!
Matteo

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