Built-in functions

Last published : Sep 21, 2026
Expressions in StyleBooks can make use of built-in functions.
For example, you can use the built-in function, str() to transform a number to a string.
str($parameters.order)
Or, you can use the built-in function, int() to transform a string into an integer.
int($parameters.priority)
The following is the list of built-in functions supported in StyleBook expressions with examples of how they can be used:
Related information

str()

The str() function transforms the input argument to a string value.
Allowed argument types:
  • string
  • number
  • TCP-port
  • boolean
  • IP address
Examples:
  • The "set-" + str(10) function returns "set-10".
  • The str(10) function returns 10.
  • The str(1.1.1.1) function returns 1.1.1.1.
  • The str(T rue) function returns "T rue".
  • The str(ADM) function returns "mas".

int()

The int() function takes a string, number, IP address, or tcpport as an argument and returns an integer.
Examples:
  • The int("10") function returns 10.
  • The int(10) function returns 10.
  • The int(ip('0.0.4.1')) function returns 1025.

bool()

The bool() function takes any type as an argument. If the argument value is false, empty, or absent, this function returns false.
Otherwise, it returns true.
Examples:
  • The bool(true) function returns true.
  • The bool(false) function returns false.
  • The bool($parameters.a) function returns false if the $parameters.a is false, empty, or absent.

len()

The len() function takes a string or a list as an argument, and returns the number of characters in a string or the number of items in a list.
Example 1:
If you define a substitution as follows:
items: ["123", "abc", "xyz"]
The len($substitutions.items) function returns 3
Example 2:
The len("NetScaler ADM") function returns 10.
Example 3:
If $parameters.vips has values ['1.1.1.1', '1.1.1.2', '1.1.1.3'], the len($parameters.vips) function returns 3.

min()

The min() function takes either a list or a series of numbers or tcp-ports as arguments, and returns the smallest item.
Examples with a series of numbers/tcp-ports:
  • The min(80, 100, 1000) function returns 80.
  • The min(-20, 100, 400) function returns -20.
  • The min(-80, -20, -10) function returns -80.
  • The min(0, 100, -400) function returns -400.
Examples with a list of numbers/tcp-ports:
  • Support $parameters.ports is a list of tcp-ports and has values: [80, 81, 8080].
    The min($parameters.ports) function returns 80.

max()

The max() function takes either a list or a series of numbers or tcp-ports as arguments, and returns the largest item.
Examples with a series of numbers/tcp-ports:
  • The max(80, 100, 1000) function returns 1000.
  • The max(-20, 100, 400) function returns 400.
  • The max(-80, -20, -10) function returns -10.
  • The max(0, 100, -400) function returns 100.
Examples with a list of numbers/tcp-ports:
  • Support $parameters.ports is list of tcp-ports and has values: [80, 81, 8080].
    The max($parameters.ports) function returns 8080.

bin()

The bin() function takes a number as an argument, and returns a string that represents the number in binary format.
Examples of expressions:
The bin(100) function returns 0b1100100.

oct()

The oct() function takes a number as an argument, and returns a string that represents the number in octal format.
Examples of expressions:
The oct(100) function returns 0144.

hex()

The hex() function takes a number as an argument, and returns a lowercase string that represents the number in hexadecimal format.
Examples of expressions:
The hex(100) function returns 0x64.

lower()

The lower() function takes a string as an argument and returns the same string in the lowercase.
Example:
The lower("ADM") function returns adm.

upper()

The upper() function takes a string as an argument and returns the same string in uppercase.
Example:
The upper("NetScaler ADM") function returns NetScaler ADM.

sum()

The sum() function takes a list of numbers or tcpports as arguments and returns the sum of the numbers in the list.
Example 1:
If you define a substitution as follows: substitutions:
list-of-numbers = [11, 22, 55]
The sum($substitutions.list-of-numbers) function returns 88.
Example 2:
If $parameters.ports is [80, 81, 82], the sum($parameters.ports) function returns 243.

pow()

The pow() function takes two numbers as arguments and returns a number that represents the first argument raised to the power of the second one.
Example:
The pow(3,2) function returns 9.

ip()

The ip() function takes an integer, string, or an IP address as an argument and returns the IP address based on the input value.
Examples:
  • Specify an IP address in the ip function:
    The ip(3.1.1.1) function returns 3.1.1.1.
  • Specify a string in the ip function:
    The ip('2.1.1.1') function returns 2.1.1.1
  • Specify an integer in the ip function:
    • The ip(12) function returns 0.0.0.12.
    • When you specify an integer as string in the ip function, it returns an equivalent IP address of the input.
      The ip('1025') function returns 0.0.4.1.
    This function also supports the integer addition and subtraction operations and returns a resultant IP address.
    • Addition: The ip(1025) + ip(12) function returns 0.0.4.13.
    • Subtraction: The ip('1025') - ip(12) function returns 0.0.3.245.
    • Combine addition and subtraction: The ip('1.1.1.1') + ip('1.1.1.1') – ip(2) returns 2.2.2.0.

base64.encode()

The base64.encode() function takes a string argument and returns the base64 encoded string.
Example:
The base64.encode("abcd") function returns YWJjZA==.

base64.decode()

The base64.decode function takes a base64 encoded string as an argument and returns the decoded string.
Example:
The base64.decode("YWJjZA==") function returns abcd.

exists()

The exists() function takes an argument of any type and returns a boolean. The return value is True if the input has any value. The return value is False If the input argument does not have a value (that is, no value).
Consider that the $parameters.monitor is an optional parameter. If you provide a value to this parameter when creating a configuration pack, exist the ($parameters.monitor) function returns True.
Otherwise, it returns False.

filter()

The filter() function takes two arguments.
Argument 1: a substitution function that takes one argument and returns a Boolean value.
Argument 2: a list.
The function returns a subset of the original list where each element evaluates to True when passed to the substitution function in the first argument.
Example:
Suppose we have defined a substitution function as follows.
Substitutions:
x(a): $a != 81
This function returns True if the input value is not equal to 81. Otherwise, it returns False.
Suppose,$parameters.ports is [81, 80, 81, 89].
The filter($substitutions.x, $parameters.ports) returns [80, 89] by removing all occurrences of 81 from the list.

if-then-else()

The function if-then-else() takes three arguments.
Argument 1: Boolean expression
Argument 2: Any expression
Argument 3: Any expression (optional)
If the expression in argument 1 evaluates to True, the function returns the value of the expression provided as argument 2.
Otherwise, if argument 3 is provided, the function returns the value of the expression in argument 3.
If argument 3 is not provided, the function returns no.
Example 1:
The if-then-else($parameters.servicetype == HTTP, 80, 443) function returns 80 if $parameters.servicetype has value HTTP. Otherwise, the function returns 443.
Example 2:
The if-then-else($parameters.servicetype == HTTP, $parameters.hport, $parameters.sport) function returns the value of $parameters.hport if $parameters.servicetype has value HTTP.
Otherwise, the function returns the value of $parameters.sport.
Example 3:
The if-then-else($parameters.servicetype == HTTP, 80) returns 80 if $parameters.servicetype has value HTTP.
Otherwise, the function does not return any value.

join()

The join() function takes two arguments:
Argument 1: list of numbers, tcp-ports, strings, or IP addresses
Argument 2: delimiter string (optional)
This function joins the elements of the list provided as argument one into a string, where each element is separated by the delimiter string provided as argument two. If argument two is not provided, then the elements in the list are joined as one string.
Example:
  • $parameters.ports is [81, 82, 83].
    • With delimiter argument:
      The join($parameters.ports, '-') function returns 81-82-83.
    • Without delimiter argument:
      The join($parameters.ports) function returns 818283.

split()

The split() function splits an input string into multiple lists depending on the specified separators. If no or blank ('') separator is specified, this function considers space as a separator and splits the string into lists.
Examples:
  • The split('Example_string_split', 's') function returns ['Example_','tring_','plit'].
  • The split('Example string split') function returns ['Example','string','split'].
  • The split('Example string split', '') function returns ['Example','string','split'].
  • The split('Example string') function returns ['Example','string'].
    This function considers continuous spaces as one space.

map()

The map() function takes two arguments;
Argument 1: Any function
Argument 2: A list of elements.
The function returns a list where each element in the list is the result of applying the map() function (argument one) to the corresponding element in argument two.
Allowed functions in argument 1:
  • Built-in functions that take one argument:
    base64.encode, base64.decode, bin, bool, exists, hex, int, ip, len, lower, upper, oct, quotewrap, str, trim, upper, url.encode, url.decode
  • Substitution functions that take at least one argument.
Example:
Suppose $parameters.nums is [81, 82, 83].
  • Map using a built-in function, str
    The map(str, $parameters.nums) function returns ["81", "82", "83"]
    The result of the map function is the list of strings where each element is string is computed by applying the str function on the corresponding element in the input list ($parameters.nums).
  • Map using a substitution function
    • Substitutions:
      add-10(port): $port + 10
    • Expression:
      The map($substitutions.add-10, $parameters.nums) function returns a list of numbers: [ 91, 92, 93 ]
The result of this map function is a list of numbers, each element is computed by applying the substitution function $substitutions.add-10 on the corresponding element in the input list ($parameters.nums).

quotewrap()

The quotewrap() function takes a string as an argument and returns a string after adding a double quote character before and after the input value.
Example:
The quotewrap("ADM") function returns "mas"

replace()

The replace() function takes three arguments:
Argument 1: string
Argument 2: string or list
Argument 3: string (optional)
The function replaces all the occurrences of argument two with argument three in argument one.
If argument three is not provided, all occurrences of argument two are removed from argument one (in other words, replaced with an empty string).
Replace a substring with another substring:
  • The replace('abcdef', 'def', 'xyz') function returns abcxyz.
    All occurrences of def are replaced with xyz.
  • replace('abcdefabc', 'def') returns abcabc.
    As there is no third argument, def is removed from the resulting string.
Specify the characters list that you want to replace in a string.
$parameters.spl_chars = ['@', '#', '!', '%']
This list contains the values that have to be replaced in an input string.
The replace('An#example@to%replace!characters', $parameters.spl_chars, '_') function returns An_example_to_replace_characters.
The output string has underscore (_) instead of characters specified in the $parameters.spl_chars list.

trim()

The trim() function returns a string where the leading and trailing whitespaces are stripped from the input string.
Example:
The trim(' abc ') function returns abc.

truncate()

The truncate() function takes two arguments:
Argument 1: string
Argument 2: number
The function returns a string where the input string in argument one is truncated to the length specified by argument two.
Example:
The truncate('NetScaler ADM', 6) returns Citrix.

distinct()

The distinct() function extracts unique items from a list input.
Examples: If $parameters.input_list is ['ADM', 'ADC', 'VPX', 'ADC', 'ADM', 'CPX'], the distinct($parameters.input_list) function returns ['ADM', 'ADC', 'VPX', 'CPX'].

url.encode()

The url.encode() function returns a string where characters are transformed using the ASCII character set according to RFC 3986.
Example:
The url.encode("a/b/c") function returns a%2Fb%2Fc.

url.decode()

The url.decode() function returns a string where the URL encoded argument is decoded in to a regular string according to RFC 3986.
Example:
The url.decode("a%2Fb%2Fc") function returns a/b/c.

is-ipv4()

The is-ipv4() function takes an IP address as an argument and returns the boolean True if the IP address is of the IPv4 format.
The is-ipv4(10.10.10.10) function returns True

is-ipv6()

The is-ipv6() function takes an IP address as an argument and returns the boolean True if the IP address is of the IPv6 format.
The is-ipv6(2001:DB8::) function returns True

startswith()

The startswith() function determines whether a string begins with a given prefix. This function requires two mandatory string arguments.
startswith(str, sub_str)
This function returns True when the string (str) starts with the substring (sub_str).
Examples:
  • The startswith('Citrix', 'Ci') function returns True.
  • The startswith('Citrix', 'iC') function returns False
  • The startswith('Citrix', 'Ab') function returns False

endswith()

The endswith() function determines whether a string ends with a given suffix. This function requires two mandatory string arguments.
endswith(str, sub_str)
This function returns True when the string (str) ends with the substring (sub_str).
Examples:
  • The endswith('Citrix', 'ix') function returns True.
  • The endswith('Citrix', 'Ix') function returns False.
  • The endswith('Citrix', 'ab') function returns False.

contains()

The contains() function determines whether a string contains a given substring. This function requires two mandatory string arguments.
contains(str, sub_str)
This function returns True when the substring (sub_str) is contained anywhere inside the string (str).
Example:
  • The contains('Citrix', 'tri') function returns True.
  • The contains('Citrix', 'Ci') function returns True.
  • The contains('Citrix', 'ti') function returns False

substring()

Use the substring() function to extract a substring from a string.
substring(str, start_index, end_index)
This function requires the two mandatory arguments and one optional integer argument.
  • str (Mandatory)
  • start_index (Mandatory)
  • end_index (Optional)
This function returns the substring from the string (str) that is between the specified index positions. If you do not specify the end index position, the function extracts the substring from the start index to the end of the string.
Note
When you specify end_index, the substring excludes the character at the end_index position.
Example:
  • The substring('Citrix', 2) function returns trix
  • The substring('Citrix', 10) function returns (")
    In this example, the function returns a blank string because it has an invalid start_index position.
  • The substring('Citrix', 2, 4) function returns tr
    In this example, the function extracts the characters between 2 and 4 index positions.
  • The substring('Citrix', -3) function returns rix
    If you want to extract characters that are at the end of the string, specify a negative value for the start_index argument.
    In this example, the function extracts the substring that includes the last three characters in the string.