[ncl-talk] determine success of ncl script via bash

[Adam Phillips]

HI Micah,
You could use isfilevar to check for a variable on a file before attempting
to read it:
http://www.ncl.ucar.edu/Document/Functions/Built-in/isfilevar.shtml
Adam

On Thu, Nov 12, 2020 at 11:44 AM Micah Sklut via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Thank you for that comprehensive answer Dave. In the specific case that I
> am encountering, there was an issue on the NCEP data, where variables were
> not included in the file. Perhaps there are ncl functions for this type of
> error check?  The solution that I started to work with is checking the
> output from the ncl command, and using grep to determine if the string
> 'fatal' exists.
>
> function ncl_error_check() {
>   if grep -q 'fatal' $1; then
>     echo 'an NCL error has occurred'
>   fi
> }
>
> ncl command.ncl > ncl_output.txt
> ncl_error_check ncl_output.txt
>
> On Thu, Nov 12, 2020 at 1:32 PM Dave Allured - NOAA Affiliate <
> dave.allured at noaa.gov> wrote:
>
>> The NCL function *status_exit* allows the user program to set the
>> integer exit status code, which can be read by the shell.  This is probably
>> what you want.  See the example and discussion on that function's doc page.
>>
>> I can think of four kinds of NCL fatal errors:
>>
>> * NCL reports a "fatal error" to the console, but the program keeps
>> running and does not exit.  This happens more often than I would like.
>> * NCL internally detects some kind of fatal error, and exits to the shell.
>> * NCL has an uncontrolled crash and exits to the shell.
>> * An NCL user program detects a problem and exits to the shell using the
>> *status_exit* function.
>>
>> Unfortunately the exit status code is undefined in the first three
>> cases.  This is why it is best for user programs to manually check for
>> predictable errors, and handle their own error exits in an intelligent
>> way.  One example is to check for missing input files with functions like
>> *isfilepresent* before blindly trying to open them with *addfile*,
>> *cbinread*, etc.
>>
>> Also I usually use an *if* statement in C shell to check the exit code.
>> Not being a bash expert, I do not understand the double pipe syntax in your
>> example.  If you think your NCL program is emitting proper exit codes, you
>> might check your bash code to make sure it is doing what you think.
>>
>>
>> On Thu, Nov 12, 2020 at 10:57 AM Micah Sklut via ncl-talk <
>> ncl-talk at mailman.ucar.edu> wrote:
>>
>>> Hi,
>>>
>>> I run a bunch of ncl script operationally in bash scripts. I'd like to
>>> be able to detect if NCL encounters a fatal error. Any suggestions on this?
>>>
>>> I've tried this without success:
>>>
>>> ncl nam_file.ncl || {
>>>     echo 'failure'
>>>     exit
>>>   }
>>>
>>> Thanks.
>>> --
>>> Micah Sklut
>>>
>>
>
> --
> Micah Sklut
>
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-- 
Adam Phillips
Associate Scientist,  Climate and Global Dynamics Laboratory, NCAR
www.cgd.ucar.edu/staff/asphilli/   303-497-1726

<http://www.cgd.ucar.edu/staff/asphilli>
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