asterisk*CLI> show functions
Installed Custom Functions:
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CALLERID              CALLERID(datatype)                   Gets or sets Caller*ID data on the channel.
LANGUAGE              LANGUAGE()                           Gets or sets the channel's language.
TIMEOUT               TIMEOUT(timeouttype)                 Gets or sets timeouts on the channel.
DB_EXISTS             DB_EXISTS(<family>/<key>)            Check to see if a key exists in the Asterisk database
DB                    DB(<family>/<key>)                   Read or Write from/to the Asterisk database
ENV                   ENV(<envname>)                       Gets or sets the environment variable specified
IF                    IF(<expr>?<true>:<false>)            Conditional: Returns the data following '?' if true else the data following ':'
EXISTS                EXISTS(<data>)                       Existence Test: Returns 1 if exists, 0 otherwise
SET                   SET(<varname>=<value>)               SET assigns a value to a function call.
ISNULL                ISNULL(<data>)                       NULL Test: Returns 1 if NULL or 0 otherwise
CDR                   CDR(<name>[|options])                Gets or sets a CDR variable
EVAL                  EVAL(<variable>)                     Evaluate stored variables.
STRFTIME              STRFTIME([<epoch>][,[timezone][,for  Returns the current date/time in a specified format.
LEN                   LEN(<string>)                        Returns the length of the argument given
REGEX                 REGEX("<regular expression>" <data>  Regular Expression: Returns 1 if data matches regular expression.
FIELDQTY              FIELDQTY(<varname>,<delim>)          Count the fields, with an arbitrary delimiter
GROUP_LIST            GROUP_LIST()                         Gets a list of the groups set on a channel.
GROUP                 GROUP([category])                    Gets or sets the channel group.
GROUP_MATCH_COUNT     GROUP_MATCH_COUNT(groupmatch[@categ  Counts the number of channels in the groups matching the specified pattern
GROUP_COUNT           GROUP_COUNT([groupname][@category])  Counts the number of channels in the specified group
CHECK_MD5             CHECK_MD5(<digest>,<data>)           Checks an MD5 digest
MD5                   MD5(<data>)                          Computes an MD5 digest
SIP_HEADER            SIP_HEADER(<name>)                   Gets or sets the specified SIP header
IAXPEER               IAXPEER(<peername>[:item])           Gets IAX peer information
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