HCL Functions¶

Standard Library¶

The following functions are all from the go-cty, go-cty-yaml and hcl libraries

abs¶

abs returns the absolute value

abs(number)

abs(-1)
# 1
abs(2)
# 2

can¶

can evaluates an expression and returns a boolean if a result can be produced without any error

can(expr)

map = {
  myvar = "myvar"
}
can1 = can(hv.map.myVar)
# true
can2 = can(hv.map.notMyVar) 
# false

ceil¶

ceil returns the ceiling value of a given number

ceil(number)

ceil(1) 
# 1
ceil(1.1) 
# 2

chomp¶

chomp removes newline characters at the end of a string.

chomp(string)

chomp("myVar\n")
# myVar

coalesce¶

coalesce returns the first of the given arguments that is not null. If all arguments are null, an error is produced.
All arguments must be of the same type apart from some cases

coalesce(any...)

coalesce(null, 2)
# 2
coalesce(null, "value")
# value

Use the three dots notation ... to expand a list

coalesce([null, "value"]...)
# value

coalescelist¶

coalescelist takes any number of list arguments and returns the first one that isn’t empty.

coalescelist(list)

coalescelist([], ["value"])
# ["value"]

Use the three dots notation ... when using list of lists

coalescelist([[], ["val1", "val2"]]...)
# ["val1", "val2"]

compact¶

compact returns a new list with any empty string elements removed.

compact(list)

compact(["", "val1", "val2"])
# ["val1", "val2"]

concat¶

concat takes one or more sequences (lists or tuples) and returns the single sequence that results from concatenating them together in order.

concat(list, list...)

concat(["val1"], ["val2", "val3"])
# ["val1", "val2", "val3"]

contains¶

contains returns a boolean if a list contains a given value

contains(list, value)

contains(["val1", "val2"], "val2")
# true

csvdecode¶

csvdecode decodes a CSV-formatted string into a list of maps

csvdecode(string)

csvdecode("col1,col2\nv1,v2\nv3,v4")
###
[
  {
    "col1" = "v1"
    "col2" = "v2"
  },
  {
    "col1" = "v3"
    "col2" = "v4"
  }
]

distinct¶

distinct returns a new list from another by removing all duplicates

distinct(list)

distinct(["v1","v1","v2"])
["v1", "v2"]

element¶

element returns a single element from a given list at the given index. If index is greater than the length of the list then it is wrapped modulo the list length

element(list, index)

element(["val1","val2"], 1)
# val2

chunklist¶

chunklist splits a single list into fixed-size chunks, returning a list of lists.

chunklist(list, size)

chunklist(["a","b"], 1)
# [["a"], ["b"]]

flatten¶

flatten takes a list and replaces any elements that are lists with a flattened sequence of the list contents.

flatten(list)

flatten([["a"], ["a","b"], ["c"]])
# ["a","a","b","c"]

floor¶

floor returns the closest whole number lesser than or equal to the given value.

floor(number)

floor(1)
# 1
floor(0.7)
# 0

format¶

format produces a string representation of zero or more values using a format string similar to the “printf” function in C.
Verbs details

format(format, values)

format("Hello %s", "world")
# Hello world

formatdate¶

formatdate reformats a timestamp given in RFC3339 syntax into another time syntax defined by a given format string.
Syntax details

formatdate(string, timestampString)

formatdate("MMM DD YYYY", "2024-01-01T00:12:00Z")
# Jan 01 2024

formatlist¶

formatlist does the same as format but for a list of strings

formatlist(formatString, values...)

formatlist("%s", ["Hello", "World"])
###
[
  "Hello",
  "World"
]

formatlist("%s %s", "hello", ["World", "You"])
###
[
  "hello World",
  "hello You",
]

indent¶

indent adds a given number of spaces to the beginnings of all but the first line in a given multi-line string.

indent(number, string)

indent(4, "hello,\nWorld\n!")
###
hello
    World
    !

int¶

int removes the fractional component of the given number returning an integer representing the whole number component, rounding towards zero.

int(number)

int(6.2)
# 6

join¶

join concatenates together the string elements of one or more lists with a given separator.

join(listOfStrings, separator)

join(" ", ["hello", "world"])
# hello world

jsondecode¶

jsondecode parses the given JSON string and, if it is valid, returns the value it represents.

jsonencode(string)

Example :

jsonencode({"hello"="world"})
# {"hello": "world"}

jsonencode¶

jsonencode returns a JSON serialization of the given value.

jsondecode(string)

Example :

jsondecode("{\"hello\": \"world\"}")
# { hello = "world" }

keys¶

keys takes a map and returns a sorted list of the map keys.

keys(map)

keys({val1=1, val2=2, val3=3})
# ["val1","val2","val3"]

length¶

length returns the number of elements in the given collection.
See strlen for strings

length(list)

length([1,2,3])
# 3

log¶

log returns returns the logarithm of a given number in a given base.

log(number, base)

log(1, 10)
# 0

lookup¶

lookup performs a dynamic lookup into a map. There are three required arguments, inputMap and key, plus a defaultValue, which is a value to return if the given key is not found in the inputMap.

lookup(inputMap, key, defaultValue)

map = { "luke" = "skywalker"}
lookup(hv.maptest, "luke", "none")
# skywalker
lookup(hv.maptest, "leia", "none")
# none

lower¶

lower is a Function that converts a given string to lowercase.

lower(string)

lower("HELLO world")
# hello world

max¶

max returns the maximum number from the given numbers.

max(numbers)

max(1,128,70)
# 128

merge¶

merge takes an arbitrary number of maps and returns a single map that contains a merged set of elements from all of the maps.

merge(maps)

merge({a="1"}, {a=[1,2], c="world"}, {d=40})
# { a = [1,2], c = "world", d = 40}

min¶

min returns the minimum number from the given numbers.

min(numbers)

min(1,128,70)
# 1

parseint¶

parseint parses a string argument and returns an integer of the specified base.

parseint(string, base)

parseint("190", 10)
# 190
parseint("11001", 2)
# 25

pow¶

pow returns the logarithm of a given number in a given base.

pow(number, power)

pow(1, 10)
# 1
pow(3, 12)
# 531441

range¶

range creates a list of numbers by starting from the given starting value, then adding the given step value until the result is greater than or equal to the given stopping value. Each intermediate result becomes an element in the resulting list.

range(startingNumber, stoppingNumber, stepNumber)

range(1, 10, 3)
# [1, 4, 7]

regex¶

regex is a function that extracts one or more substrings from a given string by applying a regular expression pattern, describing the first match.
The return type depends on the composition of the capture groups (if any) in the pattern:

If there are no capture groups at all, the result is a single string representing the entire matched pattern.
If all of the capture groups are named, the result is an object whose keys are the named groups and whose values are their sub-matches, or null if a particular sub-group was inside another group that didn't match.
If none of the capture groups are named, the result is a tuple whose elements are the sub-groups in order and whose values are their sub-matches, or null if a particular sub-group was inside another group that didn't match.
It is invalid to use both named and un-named capture groups together in the same pattern.

If the pattern doesn’t match, this function returns an error. To test for a match, call regexall and check if the length of the result is greater than zero.

regex(pattern, string)

regex("[0-9]+", "v1.2.3")
# 1

regexall¶

regexall is similar to Regex but it finds all of the non-overlapping matches in the given string and returns a list of them.

The result type is always a list, whose element type is deduced from the pattern in the same way as the return type for Regex is decided.

If the pattern doesn’t match at all, this function returns an empty list.

regexall(pattern, string)

regexall("[0-9]+", "v1.2.3")
# [1 2 3]

setintersection¶

setintersection returns a new set containing the elements that exist in all of the given sets, which must have element types that can all be converted to some common type using the standard type unification rules. If conversion is not possible, an error is returned.

setintersection(sets...)

setintersection(["val1", "val2"], ["val1", "val3"], ["val1", "val2"])
# ["val1"]

setproduct¶

setproduct computes the Cartesian product of sets or sequences.

setproduct(sets...)

setproduct(["host1", "host2"], ["stg.domain", "prod.domain"])
### 
[
  [
    "host1",
    "stg.domain"
  ],
  [
    "host2",
    "stg.domain"
  ],
  [
    "host1",
    "prod.domain"
  ],
  [
    "host2",
    "prod.domain"
  ],
]

setsubtract¶

setsubtract returns a new set containing the elements from the first set that are not present in the second set. The sets must have element types that can both be converted to some common type using the standard type unification rules. If conversion is not possible, an error is returned.

setsubtract(sets...)

setsubtract(["a", "b", "c"], ["a", "b"])
### 
["c"]

setunion¶

setunion returns a new set containing all of the elements from the given sets, which must have element types that can all be converted to some common type using the standard type unification rules. If conversion is not possible, an error is returned.

setunion(sets...)

setunion(["a", "b"], ["b", "c"], ["a", "d"])
### 
["a", "b", "c", "d"]

signum¶

signum determines the sign of a number, returning a number between -1 and 1 to represent the sign.

signum(number)

signum(-182)
# -1

slice¶

slice extracts some consecutive elements from within a list.
startIndex is inclusive, endIndex is exclusive

slice(list, startIndex, endIndex)

slice([{"a" = "b"}, {"c" = "d"}, , {"e" = "f"}], 1, 1)
# []
slice([{"a" = "b"}, {"c" = "d"}, {"e" = "f"}], 1, 2)
# [{"c" = "d"}]

sort¶

sort re-orders the elements of a given list of strings so that they are in ascending lexicographical order.

sort(list)

sort(["1", "h", "r", "p", "word"])
# ["1", "h", "p", "r", "word"]

split¶

split divides a given string by a given separator, returning a list of strings containing the characters between the separator sequences.

split(separatorString, string)

split(".", "host.domain")
# ["host", "domain"]

strlen¶

strlen is a Function that returns the length of the given string in characters.

strlen(string)

strlen("yes")
# 3

strrev¶

strrev is a Function that reverses the order of the characters in the given string.

strrev(string)

strrev("yes")
# "sey"

substr¶

substr is a Function that extracts a sequence of characters from another string and creates a new string.

substr(string, offsetNumber, length)

substr("host.domain", 0, 4)
# "host"

timeadd¶

timeadd adds a duration to a timestamp, returning a new timestamp.
Only units “inferior” or equal to h are supported.
The duration can be negative.

substr(timestamp, duration)

timeadd("2024-01-01T00:00:00Z", "-2600h10m")
# 2023-09-14T15:50:00Z

trim¶

trim removes the specified characters from the start and end of the given string.

trim(string, string)

trim("Can you do that ? Yes ?", "?")
# "Can you do that ? Yes"

trimprefix¶

trimprefix removes the specified prefix from the start of the given string.

trimprefix(stringToTrim, trimmingString)

trimprefix("please, do it", "please, ")
# "do it"

trimspace¶

trimspace removes any space characters from the start and end of the given string.

trimspace(string)

trimspace("   Hello World   ")
# "Hello World"

trimsuffix¶

trimsuffix removes the specified suffix from the end of the given string.

trimsuffix(stringToTrim, trimmingString)

trimsuffix("Hello World", " World")
# "Hello"

try¶

try is a variadic function that tries to evaluate all of is arguments in sequence until one succeeds, in which case it returns that result, or returns an error if none of them succeed.

try(expressions...)

values {
  map = {
    hello = "you"
    world = "us"
  }
  try(hv.map.do_not_exist, hv.map.world)
}
# "us"

upper¶

upper is a Function that converts a given string to uppercase.

upper(string)

upper("up")
# "UP"

values¶

values returns a list of the map values, in the order of the sorted keys. This function only works on flat maps.

values(map)

values({"a" = 1,"b" = 2})
# [1, 2]

yamldecode¶

yamldecode parses the given JSON string and, if it is valid, returns the value it represents.

yamldecode(string)

yamldecode("hello: world\narray: [1, 2, 3]")
###
{
  array = [1, 2, 3]
  hello = "world"
}

yamlencode¶

yamlencode returns a JSON serialization of the given value.

yamlencode({array = [1, 2, 3], hello = "world"})

yamlencode({array = [1, 2, 3], hello = "world"})
###
"array":
- 1
- 2
- 3
"hello": "world"

zipmap¶

zipmap constructs a map from a list of keys and a corresponding list of values.
The lenght of each list must be equal

zipmap(keysList, valuesList)

zipmap(["key1", "key2"], ["val1", "val2"])
###
{
  "key1" = "val1"
  "key2" = "val2"
}