Datasets:
Squidnutz
/
extractedtest

Dataset card Data Studio Files
xet
 Community
1
text
stringlengths
0
152
also be aware that any variables set by Asterisk will be uppercase.
Some variables, such as CHANNEL and EXTEN, are reserved by Aster‐
isk. You should not attempt to set these variables. It is popular to
write global variables in uppercase and channel variables in Pascal/
Camel case, but it is not strictly required.
There are three types of variables we can use in our dialplan: global variables, channel
variables, and environment variables. Let’s take a moment to look at each type.
Global variables
As their name implies, global variables are visible to all channels at all times. Global
variables are useful in that they can be used anywhere within a dialplan to increase
readability and manageability. Suppose for a moment that you had a large dialplan
and several hundred references to the PJSIP/0000f30A0A01 channel. Now imagine
you replaced the phone with a different unit (perhaps a different MAC address), and
had to go through your dialplan and change all of those references to PJSIP/
0000f30A0A01. Not pretty.
On the other hand, if you had defined a global variable that contained the value
PJSIP/0000f30A0A01 at the beginning of your dialplan and then referenced that
16 Specifically, what we are setting here is a channel variable.
Building an Interactive Dialplan
|
97
instead, you would have to change only one line of code to affect all places in the
dialplan where that channel was used.
Global variables should be declared in the [globals] context at the beginning of the
extensions.conf file. As an example, we will create a few global variables that store the
channel identifiers of our devices. These variables are set at the time Asterisk parses
the dialplan:
[globals]
UserA_DeskPhone=PJSIP/0000f30A0A01
UserA_SoftPhone=PJSIP/SOFTPHONE_A
UserB_DeskPhone=PJSIP/0000f30B0B02
UserB_SoftPhone=PJSIP/SOFTPHONE_B
We’ll come back to these later.
Channel variables
A channel variable is a variable that is associated only with a particular call. Unlike
global variables, channel variables are defined only for the duration of the current call
and are available only to the channels participating in that call.
There are many predefined channel variables available for use within the dialplan,
which are explained in the Asterisk wiki. You define a channel variable with exten‐
sion 203 and the Set() application:
exten => 203,1,Noop(say some digits)
same => n,Set(SomeDigits=123)
same => n,SayDigits(${SomeDigits})
same => n,Wait(.25)
same => n,Set(SomeDigits=543)
same => n,SayDigits(${SomeDigits})
You’re going to be seeing a lot more channel variables. Read on.
Environment variables
Environment variables are a way of accessing Unix environment variables from within
Asterisk. These are referenced using the ENV() dialplan function.17 The syntax looks
like ${ENV(var)}, where var is the Unix environment variable you wish to reference.
Environment variables aren’t commonly used in Asterisk dialplans, but they are avail‐
able should you need them.
17 We’ll get into dialplan functions later. Don’t worry too much about environment variables right now. They are
not important to understanding the dialplan.
98
|
Chapter 6: Dialplan Basics
Adding variables to our dialplan
Now that we’ve learned about variables, let’s put them to work in our dialplan. We’re
going to add three global variables that will associate a variable name to a channel
name:
[general]
[globals]
UserA_DeskPhone=PJSIP/0000f30A0A01
UserA_SoftPhone=PJSIP/SOFTPHONE_A
UserB_DeskPhone=PJSIP/0000f30B0B02
UserB_SoftPhone=PJSIP/SOFTPHONE_B
[sets]
exten => 100,1,Dial(${UserA_DeskPhone})
exten => 101,1,Dial(${UserA_SoftPhone})