| Re: Help needed on calling an IDL procedure from the Linux command line [message #45262] |
Thu, 25 August 2005 01:49 |
peter.albert@gmx.de
Messages: 108
Registered: July 2005
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Senior Member |
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Hi Sanjay,
I have nothing additional to say about passing parameters, but I'd like
to shed some light onto your reported "Programs can't be compiled
from a single statement mode" error. Calling IDL from the shell like
$ idl test.pro
is just the same as if you started IDL and then typed one line of your
test.pro file after the other into the IDL command line.
Thus, if you do the follwoing:
$ idl
IDL> pro test.pro
you get the same error message.
The problem disappears of course if you use one of the wrapper
solutions provided by Ken (and the others in the cited discussion) as
all those wrappers first (automaically) compile test.pro and then call
it in a way similar to
IDL> test, variable
Just another comment: if for one reason or the other you will find
yourself in a situation where you have an IDL program which will run
without input variables, and you still want to use the
$ idl test.pro
approach, then (almost) everything is fine if you just don't make the
file test.pro a routine, i.e. no "pro" or "function" command on top.
Just a list of IDL commands. However, there are two traps: If you don't
want to get stuck in the IDL session after completion of test.pro, the
last line should be
exit
in fact, if there is an "end" command in the last line, IDL will stop
compiling with a syntax error (well, you should not type "end" in the
IDL command line neither).
The next trap is a bit more tricky, and it is about for-loops or
if-clauses. Say, your test.pro file could look like this:
for i = 0, 10 do begin
print, i
print, i^2
endfor
exit
$ idl test.pro
results in
...
11
121
endfor
^
% Syntax error.
At: /home/palbert/test.pro, Line 4
The problem is that IDL works on each line after the other, and
similarily
IDL> for i = 0, 10 do begin
IDL> print, i
just produces the 11, the value of i after it went through the for-loop
11 times, trying to execute "begin". A follwoing call like
IDL> endfor
just produces the same syntax error.
The solution is that you have to make the for-loop a one-line statement
using "&". On the command line, something like
IDL> for i = 0, 10 do begin & print, i & endfor
just works fine, so the test.pro must look like
for i = 0, 10 do begin &$
print, i &$
print, i^2 &$
endfor
exit
(You need the "$" in order to tell IDL to continue in the next line).
Looks ugly but works. The same is true for if clauses.
Best regards,
Peter
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