[GRASS-dev] how to work around "Arument list too long" error in a GRASS python script ?

[Moritz Lennert]

On 11/06/15 20:05, Anna Petrášová wrote:
>
>
> On Thu, Jun 11, 2015 at 1:46 PM, Moritz Lennert
> <mlennert at club.worldonline.be <mailto:mlennert at club.worldonline.be>> wrote:
>
>     On 11/06/15 19:02, Nikos Alexandris wrote:
>
>         * Moritz Lennert <mlennert at club.worldonline.be
>         <mailto:mlennert at club.worldonline.be>> [2015-06-11 18:37:36 +0200]:
>
>             Hello,
>
>             In a python script I have the following call:
>
>             grass.run_command('r.series',
>                                   input = rate_maps,
>                                   output = sum_rates,
>                                   method = 'sum',
>                                   overwrite = True,
>                                   quiet=True)
>
>             rate_maps is a list which in one instance contains 8559 map
>             names,
>             leading to an "OSError: [Errno 7] Argument list too long".
>
>             I know that in the shell I could use xargs to work around such a
>             problem. But how to do this in python ?
>
>
>         What it the OS limit for it?
>
>
>     I suppose this is ARG_MAX ?
>
>     getconf ARG_MAX
>     2097152
>
>     A text file with all file names only uses 144551 bytes.
>
>     Or is there another limit I should look at ?
>
>
>
>             I could obviously loop through all maps and thus sum them
>             individually,
>             but this just seems horribly inefficient.
>
>             Does anyone have a better solution ?
>
>
>         - Maybe split in two or three sessions (instead of looping over
>         all)?
>
>
>     Yes, thanks, I can do that. I'll also try the file option mentioned
>     by Anna (r.series actually has one). Didn't think of that.
>
>
> Oh, I didn't know that it already has it. Good to know!

And, just for info, it solves my problem beautifully.

Moritz