Re: [ferret_users] accessing environment variables within ferret

[Brockmann Patrick <Patrick.Brockmann@xxxxxx>]

Keith Lindsay a écrit :
> 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?
Hi Keith,
You can use the SPAWN function rather than the command.

##########################
yes? show function spawn
SPAWN(STR)
   execute a system command
   STR: Unix command string (STRING)

##########################
A simple example could be:
yes? define symbol USER=`SPAWN("echo $USER")`

##########################
I often use the following lines to count
the number of lines of a large text file to be read

def sym nblines=`SPAWN("cat ($01) | wc -l")`
def axis/x=1:($nblines):1 vector_length
def grid/x=vector_length vector_grid
file/var=xpos,ypos/g=vector_grid "($01)"

##########################
Another one to read legends from a text file:
let list_textlegend=SPAWN("cat veget_type.txt")
Note that when you use a variable you don't need to use an
embedded expression (ie with characters `...`).

##########################
An one from an answer from Andrew Wittenberg
with a awk command that needs single quote
yes? let a = SPAWN("echo Hello ferreters | awk '{print $2}'")
yes? list a
            VARIABLE : SPAWN("echo Hello ferreters | awk '{print $2}'")
            X        : 1
       "ferreters"

Happy ferreting.
Patrick

--
LSCE/IPSL, Laboratoire CEA-CNRS-UVSQ
Data Analysis and Visualization Engineer
IPSL Global Climate Modelling Group
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