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pseudovariables:3.0.x [2011/09/08 14:31]
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 +====== Kamailio 3.0: Pseudo-Variables ======
 +**Version: 3.0.x**
 +
 +<​code>​
 +Authors of initial tutorial:
 +Elena-Ramona Modroiu
 +  <ramona (at) asipto.com>​
 +Bogdan-Andrei Iancu
 +  <bogdan (at) voice-system.ro>​
 +Daniel-Constantin Mierla
 +  <miconda (at) asipto.com>​
 +
 +Update for 3.0:
 +Klaus Darilion
 +</​code>​
 +
 +===== Introduction =====
 +
 +The term “pseudo-variable” is used for special tokens that can be given as parameters to different script functions and they will be replaced with a value before the execution of the function.
 +
 +The beginning of a “pseudo-variable” is marked by the character “$”. If you want to have the character “$” just double it “$$”.
 +
 +There is a set of predefined pseudo-variables,​ which have the name composed from one to three letters, and special pseudo-variables that are references to dynamic fields (AVP and Headers)
 +
 +Pseudo-Variables are implemented by various modules, most of them are provided by [b]pv[/b].
 +
 +===== Pseudo-variables usage =====
 +
 +
 +Pseudo-variables can be used with many modules, among them:
 +
 +  * acc
 +  * avpops
 +  * htable
 +  * textops
 +  * uac
 +  * xlog 
 +
 +===== The list of pseudo-variables=====
 +
 +
 +Predefined pseudo-variables are listed in alphabetical order.
 +
 +==== Pseudo-variable marker ====
 +
 +**$$** - represents the character '​$'​
 +
 +==== URI in SIP Request'​s P-Asserted-Identity header ====
 +
 +**$ai** - reference to URI in request'​s P-Asserted-Identity header (see RFC 3325)
 +
 +==== Auth Digest URI ====
 +
 +**$adu** - URI from Authorization or Proxy-Authorization header. This URI is used when calculating the HTTP Digest Response.
 +
 +==== Auth realm ====
 +
 +**$ar** - realm from Authorization or Proxy-Authorization header
 +
 +
 +==== Auth username user ====
 +
 +**$au** - user part of username from Authorization or Proxy-Authorization header
 +
 +
 +==== Auth username domain ====
 +
 +**$ad** - domain part of username from Authorization or Proxy-Authorization header
 +
 +
 +==== Auth whole username ====
 +
 +**$aU** - whole username from Authorization or Proxy-Authorization header
 +
 +==== Acc username ====
 +
 +**$Au** - username for accounting purposes. It's a selective pseudo variable (inherited from acc module). It returns $au if exits or From username otherwise.
 +
 +
 +==== Branch attributes ====
 +
 +**$branch(name)** - reference to attribute '​name'​ of a branch
 +
 +This pseudo variable gives you access to the "​additional branches"​ only, not to the "main branch"​. E.g. if there are 3 clients registered for the same AoR, after lookup() you will have one contact in the "main branch"​ and two "​additional branches"​. Using $branch() you can access the additional branches, the main branch can be accessed using $ru and $du. (Note: In branch_routes there is no distinction between the main and the additional branches - the branch_route will be called for all of them.)
 +
 +The '​name'​ can be:
 +
 +  * uri - return uri of the branch
 +  * dst_uri - return destination uri (next hop address)
 +  * q - return the q value of the branch
 +  * path - return the path vector for the branch
 +  * send_socket - return the socket to be used to send the branch
 +  * flags - return the branch flags value
 +  * count - return the number of the branches
 +
 +The PV can take an index to access a specif branch: $(branch(name)[index])
 +
 +Example:
 +
 +<​code>​
 +$var(i)=0;
 +while($var(i)<​$branch(count))
 +{
 +   ​xlog("​$(branch(uri)[$var(i)])\n"​);​
 +   ​$var(i) = $var(i) + 1;
 +}
 +</​code>​
 +
 +
 +==== Request'​s first branch ====
 +
 +**$br** - reference to request'​s first branch
 +
 +<hi #​d0d0d0>​It is R/W variable, you can assign values to it directly in configuration file (will add a new branch).</​hi>​
 +
 +==== Request'​s all branches ====
 +
 +**$bR** - reference to request'​s all branches
 +
 +==== Branch flags ====
 +
 +**$bf** - reference to branch flags of branch 0 (RURI) - decimal output
 +
 +
 +==== Branch flags ====
 +
 +**$bF** - reference to branch flags of branch 0 (RURI) - hexa output
 +
 +==== Body size ====
 +
 +**$bs** - body size
 +
 +==== Call-Id ====
 +
 +**$ci** - reference to body of call-id header
 +
 +==== Content-Length ====
 +
 +**$cl** - reference to body of content-length header
 +
 +==== CSeq ====
 +
 +**$cs** - reference to the sequence number in the cseq header. The method in the CSeq header is identical to the request method, thus use $rm to get the methode (works also for responses).
 +
 +==== Contact header ====
 +
 +**$ct** - reference to body of contact header
 +
 +
 +==== Content-Type ====
 +
 +**$cT** - reference to body of content-type header
 +
 +==== Domain of destination URI ====
 +
 +**$dd** - reference to domain of destination uri
 +
 +
 +==== Diversion header URI ====
 +
 +**$di** - reference to Diversion header URI
 +
 +==== Diversion "​privacy"​ parameter ====
 +
 +**$dip** - reference to Diversion header "​privacy"​ parameter value
 +
 +==== Diversion "​reason"​ parameter ====
 +
 +**$dir** - reference to Diversion header "​reason"​ parameter value
 +
 +
 +
 +==== Port of destination URI ====
 +
 +**$dp** - reference to port of destination uri
 +
 +==== Transport protocol of destination URI ====
 +
 +**$dP** - reference to transport protocol of destination uri
 +
 +==== Destination set ====
 +
 +**$ds** - reference to destination set
 +
 +
 +==== Destination URI ====
 +
 +**$du** - reference to destination uri
 +If loose_route() returns TRUE a destination uri is set according to the first Route header.
 +$du is also set if lookup() function of '​registrar'​ module finds contact(s) behind NAT.
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +To reset $du:
 +  $du = $null;
 +
 +==== Error class ====
 +
 +**$err.class** - the class of error (now is '​1'​ for parsing errors)
 +
 +==== Error level ====
 +
 +**$err.level** - severity level for the error
 +
 +==== Error info ====
 +
 +**$err.info** - text describing the error
 +
 +==== Error reply code ====
 +
 +**$err.rcode** - recommended reply code
 +
 +==== Error reply reason ====
 +
 +
 +**$err.rreason** - recommended reply reason phrase
 +
 +==== From URI domain ====
 +
 +**$fd** - reference to domain in URI of '​From'​ header
 +
 +==== From display name ====
 +
 +**$fn** - reference to display name of '​From'​ header
 +
 +==== From tag ====
 +
 +**$ft** - reference to tag parameter of '​From'​ header
 +
 +==== From URI ====
 +
 +**$fu** - reference to URI of '​From'​ header
 +
 +==== From URI username ====
 +
 +**$fU** - reference to username in URI of '​From'​ header
 +
 +==== SIP message buffer ====
 +
 +**$mb** - reference to SIP message buffer
 +
 +==== Flags ====
 +
 +**$mf** - reference to message/​transaction flags set for current SIP request
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +==== Flags in hexadecimal ====
 +
 +**$mF** -reference to message/​transaction flags set for current SIP request in hexa-decimal
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +==== SIP message id ====
 +
 +**$mi** - reference to SIP message id
 +
 +==== SIP message length ====
 +
 +**$ml** - reference to SIP message length
 +
 +==== Reference to null ====
 +
 +**$null** - reference to NULL (used to set a PV/AVP to null)
 +
 +==== Domain in SIP Request'​s original URI ====
 +
 +**$od** - reference to domain in request'​s original R-URI
 +
 +==== Port of SIP request'​s original URI ====
 +
 +**$op** - reference to port of original R-URI
 +
 +==== Transport protocol of SIP request original URI ====
 +
 +**$oP** - reference to transport protocol of original R-URI
 +
 +==== SIP Request'​s original URI ====
 +
 +**$ou** - reference to request'​s original URI
 +
 +==== Username in SIP Request'​s original URI ====
 +
 +**$oU** - reference to username in request'​s original URI
 +
 +==== Domain in SIP Request'​s P-Preferred-Identity header URI ====
 +
 +**$pd** - reference to domain in request'​s P-Preferred-Identity header URI (see RFC 3325)
 +
 +==== Display Name in SIP Request'​s P-Preferred-Identity header ====
 +
 +**$pn** - reference to Display Name in request'​s P-Preferred-Identity header (see RFC 3325)
 +
 +
 +==== Process id ====
 +
 +**$pp** - reference to process id (pid)
 +
 +==== Protocol of received message ====
 +
 +**$pr** or **$proto** - protocol of received message (UDP, TCP, TLS, SCTP)
 +
 +==== User in SIP Request'​s P-Preferred-Identity header URI ====
 +
 +**$pU** - reference to user in request'​s P-Preferred-Identity header URI (see RFC 3325)
 +
 +==== URI in SIP Request'​s P-Preferred-Identity header ====
 +
 +**$pu** - reference to URI in request'​s P-Preferred-Identity header (see RFC 3325)
 +
 +
 +==== Domain in SIP Request'​s URI ====
 +
 +**$rd** - reference to domain in request'​s URI
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +==== Body of request/​reply ====
 +
 +**$rb** - reference to message body
 +
 +
 +
 +==== Returned code ====
 +
 +**$rc** - reference to returned code by last invoked function
 +
 +**$retcode** - same as **$rc**
 +
 +==== Remote-Party-ID header URI ====
 +
 +**$re** - reference to Remote-Party-ID header URI
 +
 +==== SIP request'​s method ====
 +
 +**$rm** - reference to request'​s method. Works also for replies (by using the CSeq header)
 +
 +==== SIP request'​s port ====
 +
 +**$rp** - reference to port of R-URI
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +==== Transport protocol of SIP request URI ====
 +
 +**$rP** - reference to transport protocol of R-URI
 +
 +==== SIP reply'​s reason ====
 +
 +**$rr** - reference to reply'​s reason
 +
 +==== SIP reply'​s status ====
 +
 +**$rs** - reference to reply'​s status
 +
 +==== Refer-to URI ====
 +
 +**$rt** - reference to URI of refer-to header
 +
 +==== SIP Request'​s URI ====
 +
 +**$ru** - reference to request'​s URI
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +==== Username in SIP Request'​s URI ====
 +
 +**$rU** - reference to username in request'​s URI
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +==== Received IP address ====
 +
 +**$Ri** - reference to IP address of the interface where the request has been received
 +
 +==== Received port ====
 +
 +**$Rp** - reference to the port where the message was received
 +
 +==== Script flags ====
 +
 +**$sf** - reference to script flags - decimal output
 +
 +
 +==== Script flags ====
 +
 +**$sF** - reference to script flags - hexa output
 +
 +==== IP source address ====
 +
 +**$si** - reference to IP source address of the message
 +
 +==== Source port ====
 +
 +**$sp** - reference to the source port of the message
 +
 +==== Statistics ====
 +
 +**$stat(name)** - return the value of statistic item specified by '​name'​
 +
 +==== Forced socket ====
 +
 +**$fs** - reference to the forced socket for message sending (if any) in the form proto:​ip:​port
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +==== To URI Domain ====
 +
 +**$td** - reference to domain in URI of '​To'​ header
 +
 +==== To display name ====
 +
 +**$tn** - reference to display name of '​To'​ header
 +
 +==== To tag ====
 +
 +**$tt** - reference to tag parameter of '​To'​ header
 +
 +==== To URI ====
 +
 +**$tu** - reference to URI of '​To'​ header
 +
 +
 +==== To URI Username ====
 +
 +**$tU** - reference to username in URI of '​To'​ header
 +
 +
 +
 +==== String formatted time - cached ====
 +
 +**$Tf** - reference string formatted time
 +
 +Note: the system time is retrieved only once for each processed SIP message. Subsequent calls of $Tf for same SIP message will return same value.
 +
 +==== String formatted time - current ====
 +
 +**$TF** - reference string formatted time
 +
 +Note: the system time is computed for each call of $TF. Subsequent calls of $TF for same SIP message may return different values.
 +
 +==== Unix time stamp - cached ====
 +
 +**$Ts** - reference to unix time stamp
 +
 +Note: the system time is retrieved only once for each processed SIP message. Subsequent calls of $Ts for same SIP message will return same value. ​
 +
 +==== Unix time stamp - current ====
 +
 +**$TS** - reference to unix time stamp
 +
 +Note: the system time is computed for each call of $TS. Subsequent calls of $TS for same SIP message may return different values.
 +
 +==== User agent header ====
 +
 +**$ua** - reference to user agent header field
 +
 +==== AVPs ====
 +
 +**$(avp(id)[N])** - represents the value of N-th AVP identified by '​id'​.
 +
 +The '​id'​ can be:
 +
 +* "​[si]:​name"​ - name is the id of an AVP; '​s'​ and '​i'​ specifies if the id is string or integer. If missing, it is considered to be string.
 +* "​name"​ - the name is an AVP alias 
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +==== Headers ====
 +
 +
 +**$(hdr(name)[N])** - represents the body of the N-th header identified by '​name'​. If [N] is omitted then the body of the first header is printed. The first header is got when N=0, for the second N=1, a.s.o. In case of a comma-separated multi-body headers, it returns all the bodies, comma-separated. To print the last header of that type, use -1, no other negative values are supported now. No white spaces are allowed inside the specifier (before }, before or after {, [, ] symbols). When N='​*',​ all headers of that type are printed.
 +
 +The module should identify most of compact header names (the ones recognised by SIP-Router which should be all at this moment), if not, the compact form has to be specified explicitly. It is recommended to use dedicated specifiers for headers (e.g., %ua for user agent header), if they are available -- they are faster.
 +
 +==== Script variables ====
 +
 +**$var(name)** - refers to variables that can be used in configuration script, having integer or string value. This kind of variables are faster the AVPs, being referenced directly to memory location. The value of script variables persists over the processing of SIP messages, being specific per each SIP-Router process.
 +
 +Example of usage:
 +
 +<​code>​
 +$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));​
 +$var(a) = "​sip:"​ + $au + "​@"​ + $fd; -- compose a value from authentication username and From URI domain
 +
 +if( [ $var(a) & 4 ] ) {
 +  xlog("​var a has third bit set\n"​);​
 +}
 +</​code>​
 +
 +Setting a variable to null is actually initializing the value to integer '​0'​. Script variables don't have NULL value.
 +
 +**Note:** A script variable persists over the SIP-Router process in which it was initialized,​ so be sure of giving it a new value before reading it or you'll get the value asigned in any other previous message processed by the same SIP-Router process (pid).
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +
 +[b]pv[/b] module can be used to initialise the script variables.
 +
 +==== Shared variables ====
 +
 +**$shv(name)** ​ - it is a class of pseudo-variables stored in shared memory. The value of $shv(name) is visible across all openser processes. Each “shv” has single value and it is initialised to integer 0. You can use “shvset” parameter of **pv module** to initialize the shared variable. The module exports a set of MI functions to get/set the value of shared variables.
 +
 +Example - shv(name) pseudo-variable usage:
 +
 +<​code>​
 +...
 +modparam("​pv",​ "​shvset",​ "​debug=i:​1"​)
 +...
 +if ($shv(debug) == 1) {
 + xlog("​request:​ $rm from $fu to $ru\n"​);​
 +}
 +...
 +</​code>​
 +
 +<hi #​d0d0d0>​It is R/W variable (you can assign values to it directly in configuration file)</​hi>​
 +==== Broken-down time ====
 +
 +**$time(name)** - the PV provides access to broken-down time attributes.
 +
 +The '​name'​ can be:
 +  * sec - return seconds (int 0-59)
 +  * min - return minutes (int 0-59)
 +  * hour - return hours (int 0-23)
 +  * mday - return the day of month (int 0-59)
 +  * mon - return the month (int 1-12)
 +  * year - return the year (int, e.g., 2008)
 +  * wday - return the day of week (int, 1=Sunday - 7=Saturday)
 +  * yday - return the day of year (int, 1-366)
 +  * isdst - return daylight saving time status (int, 0 - DST off, >0 DST on)
 +
 +Example - time(name) pseudo-variable usage:
 +
 +<code c>
 +...
 +if ($time(year) == 2008) {
 +    xlog("​request:​ $rm from $fu to $ru in year 2008\n"​);​
 +}
 +...
 +</​code>​
 +
 +==== Selects ====
 +
 +**$sel(name)** - return the value of **select** specified by name. **select** refers a class of config variables introduced by SER 2.0, allowing to select and return parts of sip messages and not only.
 +
 +List of available selects:
 +  * http://​sip-router.org/​wiki/​cookbooks/​selects/​devel
 +
 +Example:
 +
 +<code c>
 +
 +if($sel(via[1].host)=="​10.10.10.10"​)
 +{
 +  ...
 +}
 +</​code>​
 +
 +==== Send Addr Attributes ====
 +
 +**$snd(name)** - return attributes of the address where the request is going to be sent. They are available in **onsend_route**. The name can be:
 +
 +  * ip - IP address of destination
 +  * af - address family to be used to send
 +  * port - port of destination address
 +  * proto - transport protocol to be used to send
 +
 +Example:
 +
 +<code c>
 +
 +onsend_route {
 +  if($snd(ip)=="​10.10.10.10"​)
 +  {
 +    ...
 +  }
 +}
 +</​code>​
 +
 +===== Dialog module Pseudo-Variables =====
 +
 +==== $dlg(attr) ====
 +
 +Return the attribute of the current processed dialog.
 +
 +<hi #​d0d0d0>​It is R/O variable.</​hi>​
 +
 +The '​attr'​ can be:
 +  * h_id - hash id
 +  * h_entry - hash entry
 +  * ref - reference count
 +  * state - state of dialog
 +  * to_rs - To route set
 +  * from_rs - From route set
 +  * dflags - dialog internal flags
 +  * sflags - dialog script flags
 +  * callid - sip call id
 +  * to_uri - To uri
 +  * to_tag - To tag
 +  * from_uri - From uri
 +  * from_tag - From tag
 +  * toroute - timeout route
 +  * lifetime - timeout inteval
 +  * start_ts - start timestamp
 +  * to_cseq - To CSeq
 +  * from_cseq - From CSeq
 +  * to_contact - To contact address
 +  * from_contact - From contact address
 +  * to_bindaddr - To bind address
 +  * from_bindaddr - From bind address
 +
 +==== $dlg_ctx(attr) ====
 +
 +Return the attribute of the context for current processed dialog.
 +
 +<hi #​d0d0d0>​It is R/W variable.</​hi>​
 +
 +The '​attr'​ can be:
 +  * set
 +  * flags
 +  * timeout_route
 +  * timeout_bye
 +
 +
 +===== HTable module Pseudo-Variables =====
 +
 +==== $sht(htable=>​key) ====
 +
 +Access hash table entries.
 +
 +<hi #​d0d0d0>​It is R/W variable, you can assign values to it directly in configuration file.</​hi>​
 +
 +The “htname” must be a hash table name defined via “htable” parameter.
 +
 +The “key” can be:
 +
 +  * static string - set of characters without pseudo-variables
 +  * dynamic string - set of characters that include pseudo-variables. The pseudo-variables will be evaluated at runtime.
 +
 +<​code>​
 +...
 +modparam("​htable",​ "​htable",​ "​a=>​size=4;"​)
 +...
 +$sht(a=>​$au) = 1;
 +$sht(a=>​$ru) = $fu;
 +...
 +</​code>​
 +
 +==== $shtex(htable=>​key) ====
 +
 +Access hash table entry expire value. Value represents the seconds until the htable entry will expire and be deleted from htable.
 +
 +<hi #​d0d0d0>​It is R/W variable, you can assign values to it directly in configuration file.</​hi>​
 +
 +The “htname” must be a hash table name defined via “htable” parameter and have auto-expire greater than 0.
 +
 +The “key” can be:
 +
 +  * static string - set of characters without pseudo-variables
 +  * dynamic string - set of characters that include pseudo-variables. The pseudo-variables will be evaluated at runtime.
 +
 +<​code>​
 +...
 +modparam("​htable",​ "​htable",​ "​a=>​size=4;​autoexpire=120;"​)
 +...
 +$sht(a=>​$au) = 1;
 +$shtex(a=>​$au) = 10;
 +...
 +</​code>​
 +
 +
 +==== $shtcn(htable=>​regexp) ====
 +
 +Count items matching the name by regexp.
 +
 +The “htname” must be a hash table name defined via “htable” parameter.
 +
 +The “regexp” must be a regular expression.
 +
 +<​code>​
 +...
 +modparam("​htable",​ "​htable",​ "​a=>​size=4;"​)
 +...
 +$sht(a=>​abc) = 1;
 +$shtex(a=>​ade) = 10;
 +xlog("​$shtcn(a=>​a.*)"​);​
 +...
 +</​code>​
 +
 +==== $shtcv(htable=>​regexp) ====
 +
 +Count items matching the value by regexp.
 +
 +The “htname” must be a hash table name defined via “htable” parameter.
 +
 +The “regexp” must be a regular expression.
 +
 +<​code>​
 +...
 +modparam("​htable",​ "​htable",​ "​a=>​size=4;"​)
 +...
 +$sht(a=>​abc) = "​xyz";​
 +$shtex(a=>​ade) = "​xwt";​
 +xlog("​$shtcv(a=>​x.*)"​);​
 +...
 +</​code>​
 +
 +===== Memcached module Pseudo-Variables =====
 +
 +==== $mct(key) ====
 +
 +Access hash table entries stored in the memcached server.
 +
 +<hi #​d0d0d0>​It is R/W variable, you can assign values to it directly in configuration file.</​hi>​
 +
 +The “key” can be:
 +
 +  * static string - set of characters without pseudo-variables
 +  * dynamic string - set of characters that include pseudo-variables. The pseudo-variables will be evaluated at runtime.
 +
 +<​code>​
 +...
 +$mct($au) = 1;
 +$mct($ru) = $fu;
 +$mct(test) = 1;
 +xlog("​stored value is $mct(test)"​);​
 +$mct(test) = $null; # delete it
 +xlog("​stored value is $mct(test)"​);​ # will return <​null>​
 +...
 +</​code>​
 +
 +==== $mcinc(key) ====
 +
 +Do a atomic increment operation on the value stored in memcached. You need to add a value previously.
 +
 +<hi #​d0d0d0>​It is R/W variable, you can assign values to it directly in configuration file.</​hi>​
 +
 +The “key” can be:
 +
 +  * static string - set of characters without pseudo-variables
 +  * dynamic string - set of characters that include pseudo-variables. The pseudo-variables will be evaluated at runtime.
 +
 +<​code>​
 +...
 +$mct(cnt) = 1;
 +$mcinc(cnt) = 2; # increment by 2
 +xlog("​counter is now $mct(cnt)"​);​
 +...
 +</​code>​
 +
 +==== $mcdec(key) ====
 +
 +Do a atomic decrement operation on the value stored in memcached. You need to add a value previously.
 +
 +<hi #​d0d0d0>​It is R/W variable, you can assign values to it directly in configuration file.</​hi>​
 +
 +The “key” can be:
 +
 +  * static string - set of characters without pseudo-variables
 +  * dynamic string - set of characters that include pseudo-variables. The pseudo-variables will be evaluated at runtime.
 +
 +<​code>​
 +...
 +$mct(cnt) = 10;
 +$mcdec(cnt) = 2; # decrement by 2
 +xlog("​counter is now $mct(cnt)"​);​
 +...
 +</​code>​
 +
 +===== Presence_xml Pseudo-Variables =====
 +
 +==== $xml(name=>​spec) ====
 +
 +  * name - id to refer the documet
 +  * spec - specifier:
 +    * doc - set/get the document as text
 +    * xpath:​xpath-expression - evaluate xpath expression
 +
 +Example:
 +
 +<​code>​
 +$xml(x=>​doc) = '<?​xml version="​1.0"​ encoding="​UTF-8"?><​a><​b>​test</​b></​a>';​
 +xlog("​content of node b: $xml(x=>​xpath:/​a/​b/​text())\n"​);​
 +$xml(x=>​xpath:/​a/​b) = "​1234";​
 +</​code>​
 +
 +===== TMX module Pseudo-Variables =====
 +
 +==== $T_branch_idx ====
 +
 +  * 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'​.
 +
 +==== $T_reply_code ====
 +
 +  * the code of the reply, as follows: in request_route will be the last stateful sent reply; in reply_route will be the current processed reply; in failure_route will be the negative winning reply. In case of no-reply or error, '​0'​ value is returned
 +
 +==== $T_req(pv) ====
 +
 +  * can be used in reply routes or inside the modules to get access to attributes of the request belonging to same transaction as the reply
 +
 +<​code>​
 +route {
 +  t_on_reply("​1"​);​
 +  t_relay();
 +}
 +
 +onreply_route[1] {
 +  xlog("​Request SRCIP:PORT = $T_req($si):​$T_req($sp)\n"​);​
 +}
 +</​code>​
 +
 +==== $T_rpl(pv) ====
 +
 +  * can be used in failure routes or inside the modules to get access to attributes of the winning reply belonging to same transaction as the request
 +<​code>​
 +route {
 +  t_on_failure("​1"​);​
 +  t_relay();
 +}
 +
 +failure_route[1] {
 +  xlog("​Reply SRCIP:PORT = $T_rpl($si):​$T_rpl($sp)\n"​);​
 +}
 +</​code>​
 +
 +==== $T_inv(pv) ====
 +
 +  * can be used in request routes or inside the modules to get access to attributes of the INVITE request while processing a CANCEL.
 +
 +<​code>​
 +route {
 +  if(is_method("​CANCEL"​))
 +  {
 +     ​if($T_inv($mf) & 1 )
 +     {
 +        # first flag is set in the INVITE transaction
 +     }
 +  }
 +}
 +</​code>​
 +
 +
 +===== UAC module Pseudo-Variables =====
 +
 +==== $uac_req(key) ====
 +
 +* used to build the input for uac_send_req() function of UAC module
 +
 +key can be:
 +* method - SIP method
 +* ruri - request URI
 +* furi - From URI
 +* turi - To URI
 +* ouri - Outbound proxy URI
 +* hdrs - SIP Headers
 +* body - Body
 +* all - alias for everything, useful to reset all fields (see examples)
 +
 +Examples:
 +<​code>​
 +# reset everything
 +$uac_req(all) = $null;
 +
 +#prepare UAC request
 +$uac_req(method)="​OPTIONS";​
 +$uac_req(ruri)="​sip:​kamailio.org";​
 +$uac_req(furi)="​sip:​kamailio.org";​
 +$uac_req(turi)="​sip:​kamailio.org";​
 +uac_send_req();​
 +</​code>​
 +
 +===== Special pseudo-variables in OpenSER - Escape Sequences =====
 +
 +
 +These pseudo variables are exported, and mainly used, by xlog module to print messages in many colors (foreground and background) using escape sequences. ​
 +
 +
 +==== Foreground and background colors ====
 +
 +
 +
 +$C(xy) - reference to an escape sequence. “x” represents the foreground color and “y” represents the background color.
 +
 +Colors could be:
 +
 +  * x : default color of the terminal
 +  * s : Black
 +  * r : Red
 +  * g : Green
 +  * y : Yellow
 +  * b : Blue
 +  * p : Purple
 +  * c : Cyan
 +  * w : White 
 +
 +
 +
 +
 +===== Examples =====
 +
 +
 +A few examples of usage.
 +
 +Example 1. Pseudo-variables usage
 +<code c>
 +...
 +avp_aliases="​uuid=I:​50"​
 +...
 +route {
 +...
 +    $avp(uuid)="​caller_id";​
 +    $avp(i:20)= $avp(uuid) + ": " + $fu;
 +    xdbg("​$(C(bg))avp(i:​20)$(C(xx)) [$avp(i:​20)] $(C(br))cseq$(C(xx))=[$hdr(cseq)]\n"​);​
 +...
 +}
 +...
 +</​code>​