[ncl-talk] returning value to the shell

[Jayant]

Hi Rick,
Thank you for the explanation.
I will look into the suggested link.
Best regards,
Jayant

On Mon, Oct 17, 2022 at 11:18 PM Rick Brownrigg <brownrig at ucar.edu> wrote:

> HI Jayant,
>
> I don't think that is going to work. There's a hierarchy of system
> processes going on there:  your outer shell process, which invokes ncl as a
> process, which in turn invokes an "inner" shell process with the system()
> command. The environment variable gets set in that inner process, which
> promptly terminates. There's no way to pass environment settings back up
> the hierarchy that I am aware of.
>
> I'm not a bash wizard, but what comes to mind is to write a file from ncl,
> and have your outer shell read that. So for example, print() the values you
> need and invoke ncl as:
>
>   ncl -nQ myscript.ncl >myvars.txt.    (the -n keeps ncl from enumerating
> its output lines, and the -Q keeps it from printing the copyright stuff)
>
> Then do something in your bash script similar to that described with this
> link:
>
>     https://www.cyberciti.biz/faq/unix-howto-read-line-by-line-from-file/
>
> I hope that helps...
> Rick
>
>
>
>
> On Mon, Oct 17, 2022 at 6:40 PM Jayant via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
>> Hi!
>> I have a shell script to start with where some variables (year,
>> month,tstep,variable name) are defined and passed to a ncl script. Next,
>> the ncl script performs further analysis (reading variables, analyzing).
>> The dimensionality (2-d or 3-d or 4-d) of the variable is determined inside
>> the ncl script, but I need this information back in the shell script. Is it
>> possible to get it? Roughly, I tried this
>> ----------------------
>> myscript.ncl
>> yr=toint(getenv("YEAR"))
>> mn=toint(getenv("MON"))
>> varin=getenv("VNAME")
>> ...
>> finp=addfile("modelout_"+yr+"_"+mn+".bin","r")
>> vinp=finp->varin
>> ...
>> vdimin=dimsizes(varin)
>>
>> *system("export VDIMS="+vdimin)  ; is it the correct way?*
>> ...
>> ----------------------
>> run_ncl.sh
>> #!/bin/sh
>> export YEAR=2019
>> export MON=8
>> export TSTEP=6
>> export VNAME="PREC"
>>
>> ncl myscript.ncl
>>
>> *echo $VDIMS    ; returning empty ???*
>> -----------------------------
>>
>>
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