day37.md

On the thirty seventh day, I learned the following things about Terraform.

Set the default value

• If you want to set the value to be default and not want to get asked every time then you can do it by making changes in the given code.

Change this

variable username {}

To this

variable username {
  default = "World"
}

• Now the username is set to World. If you type terraform plan, it won't ask you to enter the value.

• Instead it will show you the message. If you want to give it a value, you can do this through the command terraform plan -var "username=Bilal Khan".

Multiple variables

• You can give multiple variables also if you want to. The process is really simple and you can print them at the same time.

• In the variable.tf file, under the username variable, type another variable like this:

  variable age {
    default = "25"
  }
  

• Make changes in the hello-variable.tf file like this:

  output printname {
        value = "Hello, ${var.username}. Your age is ${var.age}"
  }
  

• Now if you type terraform plan, it won't ask you for your username and age. It will give you the values.

• If you removed the default value of age, then it will ask you for the entry when you type terraform plan.

• You can then give the age by writing this command in the terminal terraform plan -var "age=24".

• If you want to give both the username and age on the terminal without being asked, you can do this by writing terraform plan -var "username=Bilal Khan" -var "age=24".

Variable Types

• In the block of data, you can set the type also. If you want to check the list of multiple types, you can visit this website.

• Add a type in a variable like this:

  variable age {
    type = number
    default = "25"
  }
  

• If you type terraform plan -var "age=fds", it will give you an error by pointing the invalid type.

List Variables

• Create a directory by the name of list-variable and get into by writing cd list-variable.

• After that, create a file by the name of first.tf and write the following data into it.

  variable users {
      type = list
  }
  
  output printfirst {
      value = "first user is ${var.users[0]}"
  }
  

• In the above code, first the values will be taken in list and then the first value is going to be printed.

• Save the data in a file and run terraform plan. It will ask you for the values to enter. You can enter the values in a list like this: ["bilal", "ali", "khan"].

• You can also give a list of values in the terminal by typing terraform plan -var 'users=["bilal", "ali", "khan"]'

• You can set the default values by making the changes in a file like this:

  variable users {
      type = list
      default = ["bilal", "ali", "khan"]
  }
  

• Now just the terraform plan command and the result will be shown to you without asking for entry.

Functions in Terraform

• The Terraform language includes a number of built-in functions that you can call from within expressions to transform and combine values.

• Go to this website and take a look at all the functions.

Join function

• Let's take a look at an example by using some functions.

  output printfirst {
      value = "first user is ${join(", ", var.users)}"
  }
  

• If you save it and run the terraform plan command, you will get the following result.

  printfirst = "first user is bilal, ali, khan"
  

Upper function

• Write the data in an upper using the upper function.

• Make another output by the name of UpperFunc and convert the first user into upper case.

  output UpperFunc {
    value = "${upper(var.users[0])}"
  }
  

• Write terraform plan in the terminal and you will get the upper-case value.

Lower function

• Make another output by the name of LowerFunc and convert the first user into lower case.

  output LowerFunc {
    value = "${lower(var.users[0])}"
  }
  

• Write terraform plan in the terminal and you will get the lower-case value.

Title function

• Make another output by the name of TitleFunc and convert the first alphabet of a word into an upper case.

  output TitleFunc {
    value = "${title(var.users[0])}"
  }
  

• Write terraform plan in the terminal and you will get the first alphabet in an upper-case.

Explaining it in a video

Here you can get an explanation in a video. 37/60 Day of DevOps Challenge