[asterisk-users] AEL question: testing channel variables

[Steve Murphy]

On Thu, 2009-01-08 at 19:24 +0100, Klaus Darilion wrote:
> Hi!
> 
> I use the following condition:
> 
> if (${FOOBAR}=YES) {
>    ...
> }
> 
> The problem is, that if FOOBAR is not defined at all Asterisk generates 
> a warning:
> 
> WARNING[11982]: ast_expr2.fl:407 ast_yyerror: ast_yyerror():  syntax 
> error: syntax error, unexpected '=', expecting $end; Input:
> =YES
> 
> 
> Of course I could use the following code, but this bloats up the code:
> 
> 
> if (${EXISTS(${FOOBAR})}) {
>    if (${FOOBAR}=YES) {
>      ...
>    }
> }
> 
> 
> Is there another syntax to have nice looking code but avoid the warning?

Klaus--

The simplest I can think of is:

if ("${FOOBAR}"="YES") {
   ...
}

adding the quotes just makes it so if ${FOOBAR} evaluates to nothing,
then it will still end being a token, and you avoid the syntax error.

You have to keep in mind that by the time the $[ ... ] exprs are evaluated,
all ${..} constructs have been recursively evaluated away.

the wiki is a good reference for AEL2... (http://voip-info.org/wiki/view/Asterisk+AEL2
and there is a page of example snippets.

murf


> 
> thanks
> klaus

-- 
Steve Murphy <murf at digium.com>
Digium
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