[GRASS-stats] [R-sig-Geo] GISRC environment variable using initGRASS

Sun Apr 17 11:11:06 PDT 2016

On Sat, 16 Apr 2016, Roger Bär wrote:

> Thanks for the support!Please see below my comments.
>
>> Date: Fri, 15 Apr 2016 20:58:15 +0200
>> From: Roger.Bivand at nhh.no
>> To: baerroger at outlook.com
>> CC: r-sig-geo at r-project.org
>> Subject: Re: [R-sig-Geo] GISRC environment variable using initGRASS
>>
>> On Fri, 15 Apr 2016, Roger Bär wrote:
>>
>>> I am currently using the R package "rgrass7" (Version: 0.1-6) in order
>>> to command GRASS GIS (Windows7, OSGEO4W installation).
>>>
>>> I use R in order to start a GRASS environment and to script my
>>> geoprocessing. Both is working fine. However, I have problems with
>>> storing and calling the GRASS gisenv variables. Every time when I call
>>> "initGRASS" a file called "junk" is created containing GRASS gisenv
>>> variables.
>>>
>>
>> What the file is called is probably immaterial.
>>
>>>
>>> Looking at the source of the initGRASS function the section below
>>> puzzeled me somehow:
>>>
>>>  59   Sys.setenv(GISRC = paste(Sys.getenv("HOME"), "\\.grassrc7",
>>>  60     sep = ""))
>>
>> This is setting GISRC to a value
>
> Yes. The absolute path to the file (containing settings for GISDBASE, 
> LOCATION_NAME and MAPSET)
>
>>>  61   if (file.exists(Sys.getenv("GISRC")) && !override)
>>>  62     stop("A GISRC file already exists; to override, set override=TRUE")
>>>  63  Sys.setenv(GISRC = "junk")
>>
>> This is setting it again in the working directory - I don't recall why -
>> probably frustration years ago with Windows.
>
> I really do not understand the "junk" (line 63). Because GISRC is set to 
> "junk" the subsequent lines of code will write the GISRC environment 
> variables to a newly created file called "junk" in the home folder. 
> Shouldn't this line not rather be omitted? (The GRASS environment 
> variables would then be written to ".grassrc7", which in my opinion 
> would be correct)

The name of the file is immaterial, but from an R script should only be 
accessed from the value of the environment variable.

>
>>
>>>  64  cat("GISDBASE:", getwd(), "\n", file = Sys.getenv("GISRC"))
>>>  65  cat("LOCATION_NAME: <UNKNOWN>", "\n", file = Sys.getenv("GISRC"),
>>>  66     append = TRUE)
>>>  67  cat("MAPSET: <UNKNOWN>", "\n", file = Sys.getenv("GISRC"),
>>>  68     append = TRUE)
>>>  69  gisrc <- ifelse(use_g.dirseps.exe, system(paste("g.dirseps.exe -g",
>>>  70     shQuote(Sys.getenv("GISRC"))), intern = TRUE), Sys.getenv("GISRC"))
>>>  71   assign("addEXE", .addexe(), envir = .GRASS_CACHE)
>>>   72  Sys.setenv(GISRC = gisrc)
>>>
>>
>> And this sets it again. It is set, otherwise GRASS wouldn't work;
>> programmatically you'd have to use Sys.getenv("GISRC") to get the value.
>> Please provide a use case where this matters, and consider moving this
>> thread to the statsgrass list.
>
> Sorry, I do not understand what you mean with "provide a use case where 
> this matters". What do you mean with "this"?

The use of an arbitrary name in a throw-away location is of no 
significance, and could in the future be a short random name. My guess is 
that the use of "junk" may have come from different file permissions on 
unix and windows systems - if override is TRUE, R might end up trying to 
write to a file that some other process is still blocking.

Unless you can provide an R script that I can run in WinNat (not OSGeo4W - 
I do not have the time or patience to install multiple Windows versions of 
GRASS that I never use), and which demonstrates that something more is 
involved than the name of a temporary file, I can't help, because I do not 
see any real problem - the name if the file is arbitrary, and in the R 
session is accesses by Sys.getenv().

> I added the thread to the grass-stat list (and will remove r-sig from 
> the cc the next time).

OK,

Roger (Bi)

> Roger
>
>>
>> Hope this helps (doesn't clarify, but that's legacy Windows),
>>
>> Roger
>>
>>> First, why is initGRASS using ".grassrc7" for storing the GISRC file?
>>> InitGRASS is looking for the GISRC file under ".grassrc7" (line 59). However, in the package documentation [1], the GISRC file is called ".gisrc". Moreover, the GRASS documentation says that the GISRC file is stored under "/.grass7/rc"
>>>
>>> Second, what is the purpose of assigning "junk" to the GISRC environment variable?
>>> GISRC is set to "junk" (line 63) and then the GISRC value ("junk") is assigned again back to system variable GISRC. Unless I misinterpreded the code, it does not make much sense to me. Shouldn't the enviroment varibales not be written (line 64 - 68) to ".grassrc7" rather than to "junk"?
>>>
>>>
>>>
>>> I would appreciate any support or hints!
>>>
>>> Regards,
>>> Roger
>>>
>>> [1] http://https//cran.r-project.org/web/packages/rgrass7/rgrass7.pdf
>>> [2] http://grass.osgeo.org/grass70/manuals/variables.html
>>>
>>> _______________________________________________
>>> R-sig-Geo mailing list
>>> R-sig-Geo at r-project.org
>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>
>>
>> --
>> Roger Bivand
>> Department of Economics, Norwegian School of Economics,
>> Helleveien 30, N-5045 Bergen, Norway.
>> voice: +47 55 95 93 55; fax +47 55 95 91 00
>> e-mail: Roger.Bivand at nhh.no
>> http://orcid.org/0000-0003-2392-6140
>> https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
>> http://depsy.org/person/434412
>

-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 91 00
e-mail: Roger.Bivand at nhh.no
http://orcid.org/0000-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
http://depsy.org/person/434412