Asterisk readme.variables

Note: This command has been replaced by Asterisk Expressions

GENERAL ENHANCEMENTS TO EXTENSION LOGIC

QUOTING

exten => s,5,BackGround,blabla

The parameter (blabla) can be quoted ("blabla"). In this case, a comma does not terminate the field.

Also, characters special to variable substitution, expression evaluation, etc (see below), can be quoted. For example, to literally use a $ on the string "$1231", quote it with a preceeding \. Special characters that must be quoted to be used, are $ " \. (to write \ itself, use \\).

VARIABLES

Parameter strings can include variables. Variable names are arbitrary strings. They are stored in the respective channel structure.

To set a variable to a particular value, do :

exten => 1,2,SetVar(varname=value)

You can substitute the value of a variable everywhere using ${variablename}. For example, to stringwise append $lala to $blabla and store result in $koko, do:

exten => 1,2,SetVar(koko=${blabla}${lala})

There are also the following special variables:

• ${CALLERID} Caller ID
• ${CALLERIDNAME} Caller ID Name only
• ${CALLERIDNUM} Caller ID Number only
• ${EXTEN} Current extension
• ${CONTEXT} Current context
• ${PRIORITY} Current priority
• ${CHANNEL} Current channel name
• ${ENV(VAR)} Environmental variable VAR
• ${EPOCH} Current unix style epoch
• ${DATETIME} Current date time in the format: YYYY-MM-DD_HH:MM:SS
• ${UNIQUEID} Current call unique identifier
• ${SIPDOMAIN} Domain Name for current incomming SIP called, intended for host based routing

There are two reference modes – reference by value and reference by name. To refer to a variable with its name (as an argument to a function that requires a variable), just write the name. To refer to the variable’s value, enclose it inside ${}. For example, SetVar takes as the first argument (before the =) a variable name, so:

exten => 1,2,SetVar(koko=lala)
exten => 1,3,SetVar(${koko}=blabla)

stores to the variable "koko" the value "lala" and to variable "lala" the value "blabla". In fact, everything contained ${here} is just replaced with the value of the variable "here".

EXPRESSIONS

Everything contained inside a bracket pair prefixed by a $ (like $[this]) is considered as an expression and it is evaluated. Evaluation works similar to (but is done on a later stage than) variable substitution: the expression (including the square brackets) is replaced by the result of the expression evaluation. The arguments and operands of the expression MUST BE separated with spaces (take care NOT to leave ANY spaces between opening and closing square brackets and the first and last arguments).

For example, after the sequence:
exten => 1,1,SetVar,"lala=$[1 + 2]";
exten => 1,2,SetVar,"koko=$[2 * ${lala}]";
the value of variable koko is "6".

Operators are listed below in order of increasing precedence. Operators
with equal precedence are grouped within { } symbols.

expr1 | expr2
Return the evaluation of expr1 if it is neither an empty string
nor zero; otherwise, returns the evaluation of expr2.

expr1 & expr2
Return the evaluation of expr1 if neither expression evaluates to
an empty string or zero; otherwise, returns zero.

expr1 {=, >, >=, <, <=, !=} expr2
Return the results of integer comparison if both arguments are
integers; otherwise, returns the results of string comparison
using the locale-specific collation sequence. The result of each
comparison is 1 if the specified relation is true, or 0 if the
relation is false.

expr1 {+, -} expr2
Return the results of addition or subtraction of integer-valued
arguments.

expr1 {*, /, %} expr2
Return the results of multiplication, integer division, or
remainder of integer-valued arguments.

expr1 : expr2
The `:’ operator matches expr1 against expr2, which must be a
regular expression. The regular expression is anchored to the
beginning of the string with an implicit `^’.

If the match succeeds and the pattern contains at least one regu-
lar expression subexpression `\(…\)’, the string correspond-
ing to `\1′ is returned; otherwise the matching operator
returns the number of characters matched. If the match fails and
the pattern contains a regular expression subexpression the null
string is returned; otherwise 0.

Parentheses are used for grouping in the usual manner.

The parser must be parsed with bison (bison is REQUIRED – yacc cannot produce pure parsers, which are reentrant)

CONDITIONALS

There is one conditional operator – the conditional goto :

exten => 1,2,gotoif,condition?label1:label2

If condition is true go to label1, else go to label2. Labels are interpreted exactly as in the normal goto command.

"condition" is just a string. If the string is empty or "0", the condition is considered to be false, if it’s anything else, the condition is true. This is designed to be used together with the expression syntax described above, eg :

exten => 1,2,gotoif,$[${CALLERID} = 123456]?2|1:3|1

Example of use :

exten => s,2,SetVar,"vara=1"
exten => s,3,SetVar,"varb=$[${vara} + 2]"
exten => s,4,SetVar,"varc=$[${varb} * 2]"
exten => s,5,GotoIf,"$[${varc} = 6]?99|1:s|6";

• Asterisk variables
• Asterisk cmd GotoIf: Conditional statement in dial plan