Re: [ferret_users] accessing environment variables within ferret

[Andrew Wittenberg <Andrew.Wittenberg@xxxxxxxx>]

Hi Keith,

Here's the short answer for how to import an environment variable:

  let result = spawn("echo $CASE")

Note that this defines a string variable, not a symbol.  If you'd rather 
have a symbol instead, you can do this:

  define symbol result "`spawn("echo $CASE")`"

And here's a more in-depth example, showing delayed-evaluation and variable
re-use in Ferret:

% setenv ENV1 keith
% setenv ENV2 andrew
% ferret
        NOAA/PMEL TMAP
        FERRET v6.67
        Linux rh5 (gfortran) 2.6.18-238.1.1.el5P - 02/11/11
        15-Feb-11 17:51

yes? let result = spawn(command)
yes? let command = "echo $ENV1"
yes? let keep_result = "`result`"
yes? list result, keep_result
             X: 1
 Column  1: RESULT is SPAWN(COMMAND)
 Column  2: KEEP_RESULT is "keith"
          RESULT  KEEP_RESULT
I / *:    "keith" "keith"
yes? let command = "echo $ENV2"
yes? list result, keep_result
             X: 1
 Column  1: RESULT is SPAWN(COMMAND)
 Column  2: KEEP_RESULT is "keith"
           RESULT  KEEP_RESULT
I / *:    "andrew" "keith"

Cheers,

Andrew

On Tue, 15 Feb 2011, Keith Lindsay wrote:

> Hi,
>
> Is there a way to set a ferret symbol to be equal to an environment variable 
> that had been set in the environmet from which ferret was run?
>
> It looks like the environment variables are being inherited in the shell 
> created by the spawn command, so "spawn echo $CASE" is returning the value of 
> $CASE. But I haven't figure out the magic incantation to get the result of 
> this into a ferret symbol.
>
> The following doesn't work, but indicates what I'm trying to accomplish:
>
> define symbol CASE = `spawn echo $CASE`
>
> Any suggestions on how to get this to work, or pointers to another mechanism 
> to retrieve an environment variable within ferret?
>
> Thanks, Keith
>
> ******************************************************************
> Keith Lindsay                http://www.cgd.ucar.edu/oce/klindsay/
> email: klindsay@xxxxxxxx   phone: 303-497-1722   fax: 303-497-1700