Swift Programming on Linux

The steps below walk you through the process of downloading, installing & using the Swift Programming language on Linux. For this I will be using Ubuntu Linux 14.04.3 LTS version.

Setup & Configuration

1. Downloading Swift
   The first step is to download Swift from the link given below. Select the correct version of the OS.
   https://swift.org/download/#latest-development-snapshots
2. Install clang
   The next step is to get hold of clang which is  a compiler front end for C,C++,Objective-C & Objective-C++. For more information on clang:
   https://en.wikipedia.org/wiki/Clang
   http://clang.llvm.org
   To install clang run the command:
   sudo apt-get install clang
3. Extract the Swift files you downloaded and place them in a folder of your choice.
4. Next we will add swift to our path. Do that by running the command:
   export PATH=/path to your swift folder/usr/bin/:”${PATH}”
5. Verify whether it works by trying the following 2 commands
   which swift
   swift –version

Testing the REPL

1. Next we try the REPL for swift. To invoke this just type the command:
   swift
2. Write something like let myName : String = “Swift Code”
   and then hit enter.
3. Follow it by print(myName) and then hit enter.
4. You should see the output printed. This is a nice way to test individual Swift statements.

Creating a Single File Project

1. To create a file based project:
   1. Create a folder of your choice, lets call it Hello World:mkdir HelloWorld
   2. Create a manifest file for the Package with the command: touch Package.swift
   3. The source files for all your projects must be in the Sources folder, let’s create that: mkdir Sources
   4. Create a file called main.swift using an editor of your choice. Place the statement print(“Hello, World”) in it.
   5. Step out of the sources folder and then run the command to build the project: swift build
   6. The executable will be inside a hidden folder called .build/debug
   7. The name of the executable will be the same as the name of the project folder.
   8. To run it simply type: .build/debug/HelloWorld

Creating a multi file project

1. Create a folder of your choice, lets call it Hello World:mkdir CentigradeToFahrenheit
2. Create a manifest file for the Package with the command: touch Package.swift
3. The source files for all your projects must be in the Sources folder, let’s create that: mkdir Sources
4. Create a file called converter.swift using an editor of your choice.
5. Write the following code in it.:
   //note the code below is for demonstrating multi file projects & may not necessarily be accurate or correct
   func centigrade_to_fahrenheit(temperatureInCentigrade : Float) -> Float
   {
             return ((temperatureInCentigrade*9.0/5.0)+32.0)
   }
   func string_to_float(input : String) -> Float
   {
             var number : Float = 0.0;
             var result : Float = 0.0
             for charac in input.characters
             {
                       switch charac
                       {
                                 case “0”:
                                           number = 0.0;
                                 case “1”:
                                           number = 1.0;
                                 case “2”:
                                           number = 2.0;
                                 case “3”:
                                            number = 3.0;
                                 case “4”:
                                           number = 4.0;
                                 case “5”:
                                           number = 5.0;
                                 case “6”:
                                           number = 6.0;
                                 case “7”:
                                           number = 7.0;
                                 case “8”:
                                           number = 8.0;
                                 case “9”:
                                           number = 9.0;
                                 default:
                                           break
                       }
                       result = (result * 10.0) + number;
             }
             return result
   }
6. Create a second file called main.swift
7. Write the following code in it:
   if Process.arguments.count != 2
   {
             print(“USAGE: centigradeToFahrenheit 33.4”)
             print(“You are missing an argument”)
   }
   else
   {
             let temperatureInCentigrade = string_to_float(Process.arguments[1])
             print(“\(temperatureInCentigrade) is equal to \(centigrade_to_fahrenheit(temperatureInCentigrade))”)
   }
8. Step out of the sources folder and then run the command to build the project: swift build
9. The executable will be inside a hidden folder called .build/debug
10. The name of the executable will be the same as the name of the project folder.
11. To run it simply type: .build/debug/CentigradeToFahrenheit 100
    1. Try with different input values and no input value.
12. That’s it. You are now ready to start typing code in Swift.