[ncl-talk] ncl systemfunc

Sat Feb 11 09:56:52 MST 2017

Hi Rick,

This is very interesting. I did not know either that there is a dash 
shell in ubuntu?!
But you figured it out. And now the script works. Great!

I'll contact the author of the packages, perhaps he can add this 
behaviour to the "known issues".

Thanks a lot!
Matthias

On 10/02/17 22:05, Rick Brownrigg wrote:
> Hi Matthias,
>
> I think maybe we have explaination.  The so-called "brace-expansion" 
> appears to be a bash thing. I speculate your shell in your terminal 
> window is indeed bash.  However, by default, NCL under the covers 
> invokes "/bin/sh" during the systemfunc() call. On many Linux systems, 
> /bin/sh is simply a symlink to bash (that's the case on my system and 
> why things work for me).  However, apparently on Ubuntu systems, 
> /bin/sh is a symlink to a shell called "dash" (I'd never heard of it), 
> and dash is the one that does not understand brace-expansion -- you 
> can try it yourself by invoking "dash" on the command-line and then 
> trying a command that involves brace-expansion.  More on this here:
>
> http://askubuntu.com/questions/87853/what-is-default-shell-for-terminal
>
> So a solution in your case would be something like this:
>
>     files = systemfunc("bash -c 'ls /DIRECTORY/*{.nc,.hdf,.pdf}'")
>
> In particular note the "-c" switch to bash, and that the command you 
> want bash to execute is surrounded by single-quotes.
>
> Hope that helps...
> Rick
>
> On Fri, Feb 10, 2017 at 12:54 PM, Matthias Demuzere 
> <Matthias.Demuzere at ugent.be <mailto:Matthias.Demuzere at ugent.be>> wrote:
>
>     Hi Rick,
>
>     Yes... I tested this for a single string without curly brackets
>     (eg. *.nc) and that works fine ...
>     Does this indicate there is somehow a system dependency, even
>     though the curly brackets do work directly in the terminal? Quite
>     puzzling, no?
>
>     Matthias
>
>     On 10 Feb 2017 18:30, Rick Brownrigg <brownrig at ucar.edu
>     <mailto:brownrig at ucar.edu>> wrote:
>
>         Hi Matthias,
>
>         That is very odd -- it works for me, both at bash command line
>         and using systemfunc() from within NCL.  Can you get
>         systemfunc to return files from a directory without using "{}"
>         notation, .i.e, "ls *" for example? Or simply "ls foo" where
>         the file foo is known to exist in the current directory?
>
>         Rick
>
>         On Fri, Feb 10, 2017 at 10:15 AM, Matthias Demuzere
>         <matthias.demuzere at ugent.be
>         <mailto:matthias.demuzere at ugent.be>> wrote:
>
>             Dear all,
>
>             I am currently testing the CVDP
>             (http://www.cesm.ucar.edu/working_groups/CVC/cvdp/
>             <http://www.cesm.ucar.edu/working_groups/CVC/cvdp/>) which
>             is written in ncl.
>             Currently the software does not run because it can't find
>             the proper datasets.
>
>             Finding the data is driven by the *systemfunc* command
>             using curly brackets (multiple options).
>             For example, within ncl, I want to list all files that
>             have one of the following extension: .nc, .hdf, .pdf.
>
>             This I do with:
>             myFiles = systemfunc("ls /DIRECTORY/*{.nc,.hdf,.pdf}")
>
>             If I fo this in ncl, I get an error: ls: cannot access
>             '/DIRECTORY/*{.nc,.hdf,.pdf}': No such file or directory
>
>             Yet, when pasting ls /DIRECTORY/*{.nc,.hdf,.pdf} directly
>             in my system (ubuntu 16.04, 64bit) terminal, I do get a
>             list of the finals with this extension. So the expected
>             result.
>
>             I have tested this in ncl-6.3.0 and 6.2.1, but I have the
>             same problem in both.
>             Did anyone else notice this before? Any idea on how to fix
>             this?
>
>             Thanks!
>
>             Regards,
>             Matthias
>
>
>             -- 
>             Post-doctoral Research Fellow
>             _____________________________
>
>             UGent [Home]
>             Department of Forest and Water Management
>             Laboratory for Hydrology and Water Management
>             Coupure links 653, B-9000 Ghent, Belgium
>             Email:Matthias.demuzere at UGent.be <mailto:Matthias.demuzere at UGent.be>
>             Web:http://www.ugent.be/bw/dfwm/en/research/LHWM/staff/matthias
>             <http://www.ugent.be/bw/dfwm/en/research/LHWM/staff/matthias>
>
>             KU Leuven [Affiliated]
>             Department of Earth & Environmental Sciences
>             Division of Geography and Tourism / Regional climate studies
>             Celestijnenlaan 200E, B-3001 Heverlee (Leuven), Belgium
>             Email:matthias.demuzere at kuleuven.be
>             <mailto:matthias.demuzere at kuleuven.be>
>             Web:https://ees.kuleuven.be/geography/rcs
>             <https://ees.kuleuven.be/geography/rcs>
>
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-- 
Post-doctoral Research Fellow
_____________________________

UGent [Home]
Department of Forest and Water Management
Laboratory for Hydrology and Water Management
Coupure links 653, B-9000 Ghent, Belgium
Email: Matthias.demuzere at UGent.be
Web: http://www.ugent.be/bw/dfwm/en/research/LHWM/staff/matthias

KU Leuven [Affiliated]
Department of Earth & Environmental Sciences
Division of Geography and Tourism / Regional climate studies
Celestijnenlaan 200E, B-3001 Heverlee (Leuven), Belgium
Email: matthias.demuzere at kuleuven.be
Web: https://ees.kuleuven.be/geography/rcs
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