GENERAL ENCHANCEMENTS 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
${EPOCH} Current unix style epoch
${DATETIME} Current date time in the format: YYYY-MM-DD_HH:MM:SS
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";