Terraform Functions
Hello Everyone
Welcome to CloudAffaire and this is Debjeet.
In the last blog post, we have discussed terraform modules registry.
https://cloudaffaire.com/terraform-modules-registry/
In this blog post, we will discuss terraform functions. Terraform language includes a number of built-in functions that you can call from within expressions to transform and combine values. The general syntax for function calls is a function name followed by comma-separated arguments in parentheses
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Next, we are going to explain terraform functions with examples. We will use terraform console for this demo.
Terraform functions:
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##-------------------------- ## Terraform: Functions ## ##-------------------------- ## Open terraform console terraform console ####################### ## Numeric Functions ## ####################### ## abs(number): returns the absolute value of the given number. abs(-19.86) #returns 19.86 ## ceil(number): returns the closest whole number that is greater than or equal to the given value ceil(7.1) #returns 8 ## floor(number): returns the closest whole number that is less than or equal to the given value floor(7.1) #returns 7 ## log(number, base): log returns the logarithm of a given number in a given base. log(16,2) #returns 4 ## max(N1,N2,..Nn): takes one or more numbers and returns the greatest number from the set. max(3,2,6,8.8,7) #returns 8.8 ## min(N1,N2,..Nn): takes one or more numbers and returns the smallest number from the set. min(3,2,6,8.8,7) #returns 2 ## pow(number,power): calculates an exponent, by raising its first argument to the power of the second argument. pow(8,2) #returns 64 ## signum(number): determines the sign of a number, returning a number between -1 and 1 to represent the sign. signum(-4) #returns -1 signum(4) #returns 1 ###################### ## String Functions ## ###################### ## chomp("string"): removes newline characters at the end of a string. chomp("cloudaffaire\n") #returns cloudaffaire (**only removes \n from end) ## format(spec, values...): produces a string by formatting a number of other values according to a specification string format("Welcome, to %s", "CloudAffaire") #returns Welcome, to CloudAffaire format("The year is %d", 2019) #returns The year is 2019 format("%4.4f+", 3.86) #returns 3.8600+ #spec: https://www.terraform.io/docs/configuration/functions/format.html ## formatlist(spec, values...): formatlist produces a list of strings by formatting a number of other values ## according to a specification string. The specification string uses the same syntax as format. formatlist("www.%s.com",list("azure","aws","google")) #returns [www.azure.com,www.aws.com,www.google.com] ## indent(num_spaces, string): adds a given number of spaces to the beginnings of all but the first line in a given multi-line string. indent(8,"hi, \n welcome \n to \n cloudaffaire") #1st line hi has no indentaton ## join(separator, list): produces a string by concatenating together all elements of a given list of strings with the given delimiter. join(".",list("www","google","com")) #returns www.google.com ## lower(string): converts all cased letters in the given string to lowercase. lower("CLOUDAFFAIRE") #returns cloudaffaire ## upper(string): converts all cased letters in the given string to uppercase. upper("cloudaffaire") #returns CLOUDAFFAIRE ## replace(string, substring, replacement): searches a given string for another given substring, ## and replaces each occurrence with a given replacement string. replace("www.google.com","google","cloudaffaire") #returns www.cloudaffaire.com ## split(separator, string): produces a list by dividing a given string at all occurrences of a given separator. split(".","www.google.com") #returns ["www","google","com"] ## strrev(string): reverses the characters in a string. Note that the characters are treated as Unicode characters strrev("google") #returns: "elgoog" (only supported in terraform version 0.12 or later) ## substr(string, offset, length): extracts a substring from a given string by offset and length. substr("www.google.com",4,6) #returns google ## title(string): converts the first letter of each word in the given string to uppercase. title("welcome to cloudaffaire") #returns Welcome To Cloudaffaire ## trimspace(string): removes any space characters from the start and end of the given string. trimspace(" hello, all ") #returns "hello, all" ########################## ## Collection Functions ## ########################## ## chunklist(list, chunk_size): splits a single list into fixed-size chunks, returning a list of lists. chunklist(list("a","b","c","d","e","f"),3) #returns [["a","b","c"],["d","e","f"]] ## coalesce(strings\numbers): takes any number of arguments and returns the first one that isn't null or an empty string. coalesce("",1,"a") #returns 1 ## coalescelist(list1, list2, .. listn): takes any number of list arguments and returns the first one that isn't empty. coalescelist(list(),list("a","b","c"),list("d","e")) #returns ["a","b","c",] ## compact(list(string)): takes a list of strings and returns a new list with any empty string elements removed. compact(list("a","","c","","d")) #returns ["a","c","d"] ## concat(list1, list2, .. listn): takes two or more lists and combines them into a single list. concat(list("a","b"),list("c","d"),list("e","f")) #returns ["a","b","c","d","e","f"] ## contains(list, value): determines whether a given list or set contains a given single value as one of its elements. contains(list("a","b","c"),"a") #returns true contains(list("a","b","c"),"d") #returns false ## distinct(list): takes a list and returns a new list with any duplicate elements removed. distinct(list("a","b","b","c")) #returns ["a","b","c",] ## element(list, index): retrieves a single element from a list. element(list("a","b","c"),2) #returns c #index start from 0 ## index(list, value): finds the element index for a given value in a list. index(list("a","b","c"),"b") #returns 1 ## flatten(list(list1,list2,..,listn)): takes a list and replaces any elements that are lists with a flattened sequence of the list contents. flatten(list(list("a","b"),list("c"),list(),list("d","e"))) #returns ["a","b","c","d","e",] ## keys(map): takes a map and returns a list containing the keys from that map. keys(map("name","debjeet","sex","male")) #returns ["name","sex",] ## length(list\map\string): determines the length of a given list, map, or string. length(list("a","b")) #returns 2 length("debjeet") #returns 7 length(map("name","debjeet","sex","male")) #returns 2 ## list(): takes an arbitrary number of arguments and returns a list containing those values in the same order. list("a","b","c") #returns ["a","b","c",] ## lookup(map, key, default): retrieves the value of a single element from a map, given its key. #If the given key does not exist, a the given default value is returned instead. lookup(map("name","debjeet","sex","male"),"sex","not found!") #returns male lookup(map("name","debjeet","","male"),"gender","not found!") #returns not found! ## map("key1","value1","key2","value2",...,"keyn","valuen"): takes an even number of arguments and returns a map whose elements ## are constructed from consecutive pairs of arguments. map("name","debjeet","sex","male") #returns {"name" = "debjeet" "sex" = "male"} ## matchkeys(valueslist, keyslist, searchset): constructs a new list by taking a subset of elements from one list whose indexes ## match the corresponding indexes of values in another list. matchkeys(list("a","b","c"),list("one","two","three"),list("two")) #returns b matchkeys(list("a","b","c"),list("one","two","three"),list("one")) #returns a matchkeys(list("a","b","c"),list("one","two","three"),list("three")) #returns c ## merge(map1,map2,..,mapn): takes an arbitrary number of maps and returns a single map that ## contains a merged set of elements from all of the maps. merge(map("a","one"),map("b","two"),map("c","three")) #returns {"a" = "one" "b" = "two" "c" = "three"} #reverse(list): takes a sequence and produces a new sequence of the same length with all of #the same elements as the given sequence but in reverse order. reverse(list("a","b","c")) #returns: ["c","b","a",] (only supported in terraform version 0.12 or later) ## setintersection(sets...): takes multiple sets and produces a single set containing only the elements that all of the given sets have in common. setintersection(list("a","b"),list("b","c"),list("b","d")) #returns ["b",] (only supported in terraform version 0.12 or later) ## setproduct(sets...): finds all of the possible combinations of elements from all of the given sets by computing the cartesian product. setproduct(list("a","b"),list("c","d")) #returns [["a","c"],["a","d"],["b","c"],["b","d"],] (only supported in terraform version 0.12 or later) ## setunion(sets...): takes multiple sets and produces a single set containing the elements from all of the given sets. #In other words, it computes the union of the sets. setunion(list("a","b"),list("c","d")) #returns ["a","b","c","d",] (only supported in terraform version 0.12 or later) ## slice(list, startindex, endindex): extracts some consecutive elements from within a list slice(list("zero","one","two","three"),1,3) #returns ["one","two"] ## sort(list): takes a list of strings and returns a new list with those strings sorted lexicographically. sort(list("d","c","a","b")) #returns ["a","b","c","d",] ## transpose(): takes a map of lists of strings and swaps the keys and values to produce a new map of lists of strings. transpose(map("a",list("one","two"),"b",list("three","four"))) #returns {"four"=["b",] "one"=["a",] "three"=["b",] "two"=["a",]} ## values(map): takes a map and returns a list containing the values of the elements in that map. values(map("name","debjeet","sex","male")) #returns ["debjeet","male",] ## zipmap(keyslist, valueslist): constructs a map from a list of keys and a corresponding list of values. zipmap(list("name","sex"),list("debjeet","male")) #returns {"name" = "debjeet" "sex" = "male"} ######################## ## Encoding Functions ## ######################## ## base64encode(string): applies Base64 encoding to a string. base64encode("cloudaffaire") #returns Y2xvdWRhZmZhaXJl ## base64gzip(string): compresses a string with gzip and then encodes the result in Base64 encoding. base64gzip("cloudaffaire") #returns H4sIAAAAAAAA/0rOyS9NSUxLS8wsSgUAAAD//wEAAP//38z9sQwAAAA= ## base64decode(string): takes a string containing a Base64 character sequence and returns the original string. base64decode("Y2xvdWRhZmZhaXJl") #returns cloudaffaire ## csvdecode(string): decodes a string containing CSV-formatted data and produces a list of maps representing that data. csvdecode("a,b,c\n1,2,3\n") #returns [{"a"="1" "b"="2" "c"="3"},] (only supported in terraform version 0.12 or later) ## jsonencode(): encodes a given value to a string using JSON syntax. jsonencode(map("name","debjeet")) #returns {"name":"debjeet"} ## jsondecode(): interprets a given string as JSON, returning a representation of the result of decoding that string. jsondecode("{\"name\":\"debjeet\"}") #returns {"name" = "debjeet"} (only supported in terraform version 0.12 or later) ## urlencode(): applies URL encoding to a given string. urlencode("https://cloudaffaire.com/?s=terraform") #returns https%3A%2F%2Fcloudaffaire.com%2F%3Fs%3Dterraform ########################## ## Filesystem Functions ## ########################## ## dirname(string): takes a string containing a filesystem path and removes the last portion from it. dirname("/home/ec2-user/terraform/main.tf") #returns /home/ec2-user/terraform ## pathexpand(): takes a filesystem path that might begin with a ~ segment, ## and if so it replaces that segment with the current user's home directory path. pathexpand("~/.ssh/id_rsa") #returns /home/ec2-user/.ssh/id_rsa ## basename(string): takes a string containing a filesystem path and removes all except the last portion from it. basename("/home/ec2-user/terraform/main.tf") #returns main.tf ## file(path): reads the contents of a file at the given path and returns them as a string file("/home/ec2-user/terraform/main.tf") #returns content of main.tf ## fileexists(path): determines whether a file exists at a given path. fileexists("/home/ec2-user/terraform/main.tf") #returns true if main.tf exist (only supported in terraform version 0.12 or later) ## filebase64(path): reads the contents of a file at the given path and returns them as a base64-encoded string. filebase64("/home/ec2-user/terraform/main.tf") #returns main.tf content as base64 data. (only supported in terraform version 0.12 or later) ## templatefile(path, vars): reads the file at the given path and renders its content as a template using a supplied set of template variables. ########################### ## Date & Time Functions ## ########################### ## formatdate(spec, timestamp): converts a timestamp into a different time format. formatdate("MMM DD, YYYY", "2018-01-02T23:12:01Z") #returns Jan 02, 2018 (only supported in terraform version 0.12 or later) #spec: https://www.terraform.io/docs/configuration/functions/formatdate.html ## timeadd(timestamp, duration): adds a duration to a timestamp, returning a new timestamp. ## duration is a string representation of a time difference, consisting of sequences of number and unit pairs, like "1.5h" or "1h30m". ## The accepted units are "ns", "us" (or "µs"), "ms", "s", "m", and "h". ## The first number may be negative to indicate a negative duration, like "-2h5m". timeadd("2019-05-10T00:00:00Z", "10m") #returns 2019-05-10T00:10:00Z ## timestamp(): returns the current date and time. timestamp() ############################ ## IP & Network Functions ## ############################ ## cidrhost(prefix, hostnum): calculates a full host IP address for a given host number within a given IP network address prefix. cidrhost("10.0.0.0/16", 4) #returns 10.0.0.4 cidrhost("10.0.0.0/16", -4) #returns 10.0.255.252 ## cidrnetmask(prefix): converts an IPv4 address prefix given in CIDR notation into a subnet mask address. cidrnetmask("10.0.0.0/16") #returns 255.255.0.0 cidrnetmask("10.0.0.0/24") #returns 255.255.255.0 ## cidrsubnet(prefix, newbits, netnum): cidrsubnet calculates a subnet address within given IP network address prefix. ## prefix must be given in CIDR notation ## newbits is the number of additional bits with which to extend the prefix. ## netnum is a whole number that can be represented as a binary integer with no more than newbits binary digits cidrsubnet("10.0.0.0/16",8,2) #returns 10.0.2.0/24 cidrsubnet("10.0.0.0/24",8,1) #returns 10.0.0.1/32 ## Exit terraform console exit |
Hope you have enjoyed this article. In the next blog post, we will discuss terraform expressions.
For the complete list of terraform functions, please refer below terraform documentation
https://www.terraform.io/docs/configuration/functions.html
To get more details on terraform, please refer below terraform documentation.
https://www.terraform.io/docs/index.html