注意： Opensips的版本为2.4.x
参考文献地址 https://www.opensips.org/Documentation/Script-CoreVar-2-4

变量语法

name

其实是“type”，因为它分为几种，

1. 标量/脚本变量var
2. 键值对avp （Attribute Value Pair）
3. 系统变量/伪变量PV (pseudo variables)
4. 转移字符串

subname

就是对应type的变量name

index

如果是avp和PV，可以储存多个值，这里就可以使用index来索引。注意，它支持负数，表述从后往前

transformation

就是对取出的value做变换，如截取长度，取子字符串等

context

主要是区别request和reply两个方向的，如果不清楚的话，可以参考学习笔记一

标量/脚本变量

下面是官网的例子

$var(a) = 2;  # sets the value of variable 'a' to integer '2'
$var(a) = "2";  # sets the value of variable 'a' to string '2'
$var(a) = 3 + (7&(~2)); # arithmetic and bitwise operation
$var(a) = "sip:" + $au + "@" + $fd; # compose a value from authentication username and From URI domain

# using a script variable for tests
if( [ $var(a) & 4 ] ) {
  xlog("var a has third bit set\n");
}

AVP变量

TM模块有个参数onreply_avp_mode，这个参数如果设置为0（默认为0），则AVP的生命周期只有request route，branch route以及failure route阶段，reply route阶段没有；但是有意思的是，此时，var的生命周期是整个dialog。
如果设置为1，AVP的生命周期会包含request route，branch route以及failure route阶段，reply route阶段。但是只有一个transaction内的所有阶段。新的transaction是没有继承的；此时，var的生命周期只有一个transactin的equest route，branch route阶段。

modparam("tm", "onreply_avp_mode", 1)

官网的例子

例子1， 跨route阶段保存值

# enable avps in onreply route
modparam("tm", "onreply_avp_mode", 1)
...
route{
...
$avp(tmp) = $Ts ; # store the current time (at request processing)
...
t_onreply("1");
t_relay();
...
}

onreply_route[1] {
    if (t_check_status("200")) {
        # calculate the setup time
        $var(setup_time) = $Ts - $avp(tmp);
    }
}

例子2 多值操作

$avp(17) = "one";
# we have a single value
$avp(17) = "two";
# we have two values ("two","one")
$avp(17) = "three";
# we have three values ("three","two","one")

xlog("accessing values with no index: $avp(17)\n");
# this will print the first value, which is the last added value -> "three"

xlog("accessing values with no index: $(avp(17)[2])\n");
# this will print the index 2 value (third one), -> "one"

# remove the last value of the avp; if there is only one value, the AVP itself will be destroyed
$avp(17) = NULL;

# delete all values and destroy the AVP
avp_delete("$avp(17)/g");

# delete the value located at a certain index 
$(avp(17)[1]) = NULL;

#overwrite the value at a certain index
$(avp(17)[0]) = "zero";

PV 系统变量

PV	Header Full Name	Description
$ai	URI in SIP Request's P-Asserted-Identity header	reference to URI in request's P-Asserted-Identity header (see RFC 3325)
$adu	Authentication Digest URI	URI from Authorization or Proxy-Authorization header. This URI is used when calculating the HTTP Digest Response.
$ar	Authentication realm	realm from Authorization or Proxy-Authorization header
$au	Auth username user	user part of username from Authorization or Proxy-Authorization header
$ad	Auth username domain	domain part of username from Authorization or Proxy-Authorization header
$an	Auth nonce	the nonce from Authorization or Proxy-Authorization header
$auth.resp	Auth response	the authentication response from Authorization or Proxy-Authorization header
$auth.nonce	Auth nonce	the nonce string from Authorization or Proxy-Authorization header
$auth.opaque	Auth opaque	the opaque string from Authorization or Proxy-Authorization header
$auth.alg	Auth algorithm	the algorithm string from Authorization or Proxy-Authorization header
$auth.qop	Auth QOP	the value of qop parameter from Authorization or Proxy-Authorization header
$auth.nc	Auth nonce count (nc)	the value of nonce count parameter from Authorization or Proxy-Authorization header
$aU	Auth whole username	whole username from Authorization or Proxy-Authorization header
$Au	Acc username	username for accounting purposes. It's a selective pseudo variable (inherited from acc module). It returns $au if exits or From username otherwise.
$argv		provides access to command line arguments specified with '-o' option
$af	Address family	The address family of the received SIP message. It's value is "INET" if the message was received over IPv4 or "INET6" if the message was received over IPv6
$bf	Branch flags	displays a list with the branch flags set for the current SIP request
$branch	Branch	this variable is used for creating new branches by writing into it the value of a SIP URI
$ci	Call-Id	reference to body of call-id header
$cl	Content-Length	reference to body of content-length header
$cs	CSeq number	reference to cseq number from cseq header
$ct	Contact instance	reference to contact instance/body from the contact header. A contact instance is display_name + URI + contact_params. As a Contact header may contain multiple Contact instances and a message may contain multiple Contact headers, an index was added to the $ct variable
$cT	Content-Type	reference to body of Content-Type header and also the content-type headers inside a multi-part body
$dd	Domain of destination URI	reference to domain of destination uri (read/write)
$di	Diversion header URI	reference to Diversion header URI
$dip	Diversion "privacy" parameter	reference to Diversion header "privacy" parameter value
$dir	Diversion "reason" parameter	reference to Diversion header "reason" parameter value
$dp	Port of destination URI	reference to port of destination uri(read/write)
$dP	Transport protocol of destination URI	reference to transport protocol of destination uri
$ds	Destination set	reference to destination set
$du	Destination URI	reference to destination uri (outbound proxy to be used for sending the request) If loose_route() returns TRUE a destination uri is set according to the first Route header. (read/write)
$err.class	Error class	the class of error (now is '1' for parsing errors)
$err.level	Error level	severity level for the error
$err.info	Error info	text describing the error
$err.rcode	Error reply code	recommended reply code
$err.rreason	Error reply reason	recommended reply reason phrase
$fd	From URI domain	reference to domain in URI of 'From' header
$fn	From display name	reference to display name of 'From' header
$fs	Forced socket	reference to the forced socket for message sending (if any) in the form proto:ip:port (read/write)
$ft	From tag	reference to tag parameter of 'From' header
$fu	From URI	reference to URI of 'From' header
$fU	From URI username	reference to username in URI of 'From' header
$log_level	OpenSIPS Log level	changes the log level for the current process (read/write)
$mb	SIP message buffer	reference to SIP message buffer
$mf	Message Flags	displays a list with the message/transaction flags set for the current SIP request
$mi	SIP message ID	reference to SIP message id
$ml	SIP message length	reference to SIP message length
$od	Domain in SIP Request's original URI	reference to domain in request's original R-URI
$op	Port of SIP request's original URI	reference to port of original R-URI
$oP	Transport protocol of SIP request original URI	reference to transport protocol of original R-URI
$ou	SIP Request's original URI	reference to request's original URI
$oU	Username in SIP Request's original URI	reference to username in request's original URI
$param(idx)	Route parameter	retrieves the parameters of the route. The index can be an integer, or a pseudo-variable (index starts at 1).
$pd	Domain in SIP Request's P-Preferred-Identity header URI	reference to domain in request's P-Preferred-Identity header URI (see RFC 3325)
$pn	Display Name in SIP Request's P-Preferred-Identity header	reference to Display Name in request's P-Preferred-Identity header (see RFC 3325)
$pp	Process id	reference to process id (pid)
$pr	Protocol of received message	protocol of received message (UDP, TCP, TLS, SCTP, WS)
$pU	User in SIP Request's P-Preferred-Identity header URI	reference to user in request's P-Preferred-Identity header URI (see RFC 3325)
$pu	URI in SIP Request's P-Preferred-Identity header	reference to URI in request's P-Preferred-Identity header (see RFC 3325)
$rd	Domain in SIP Request's URI	reference to domain in request's URI (read/write)
$rb	Body of request/reply	reference to the body or a body part of the SIP message
$rc	Returned code	reference to returned code by last invoked function
$re	Remote-Party-ID header URI	reference to Remote-Party-ID header URI
$rm	SIP request's method	reference to request's method
$rp	SIP request's port	reference to port of R-URI (read/write)
$rP	Transport protocol of SIP request URI	reference to transport protocol of R-URI
$rr	SIP reply's reason	reference to reply's reason
$rs	SIP reply's status	reference to reply's status
$rt	Refer-to URI	reference to URI of refer-to header
$ru	SIP Request's URI	reference to request's URI (read/write)
$rU	Username in SIP Request's URI	reference to username in request's URI (read/write)
$ru_q	Q value of the SIP Request's URI	reference to q value of the R-URI (read/write)
$Ri	Received IP address	reference to IP address of the interface where the request has been received
$Rp	Received port	reference to the port where the message was received
$si	IP source address	reference to IP source address of the message
$sp	Source port	reference to the source port of the message
$td	To URI Domain	reference to domain in URI of 'To' header
$tn	To display name	reference to display name of 'To' header
$tt	To tag	reference to tag parameter of 'To' header
$tu	To URI	reference to URI of 'To' header
$tU	To URI Username	reference to username in URI of 'To' header
$time(format)	Formatted date and time	returns the string formatted time according to UNIX date (see: man date).
$T_branch_idx	Branch index	the index (starting with 1 for the first branch) of the branch for which is executed the branch_route[]. If used outside of branch_route[] block, the value is '0'. This is exported by TM module
$Tf	String formatted time
$Ts	Current unix time stamp in seconds
$Tsm	Current microseconds of the current second
$TS	Startup unix time stamp
$ua	User agent header	reference to user agent header field
$(hdr(name)[N]) $(hdrcnt(name)	SIP Headers	represents the body of the N-th header identified by 'name'.
$rT	Route Type	Holds the current route type as a string
$cfg_line $cfg_file	Current script line and file