This post updated for Xcode 6.1<\/i><\/p>\n
One of the great features of swift is it’s ability to be used on the command line. It’s actually really easy to do, and I’ll show you how to make an executable Swift file in this tutorial.<\/p>\n
First let’s create a new Swift file. In any text editor, create a new file and save it as Hello.swift.<\/p>\n
In order to make this file executable we need to give it permissions. In the terminal app, navigate to your file using the cd command, and then type this:<\/p>\n
\r\nchmod +x Hello.swift\r\n<\/pre>\nNow open up your Swift file. We’re going to tell it to use xcrun to run our code.
\nFirst, let’s get a simple script going that prints a response to the console:<\/p>\n\r\n#!\/usr\/bin\/env xcrun swift\r\n\r\nprintln(\"Hello World!\")\r\n<\/pre>\nThis is great, but what about arguments? It’s very common for a script to take some arguments, do something with them, and then return a result.
\nLet’s say we wanted to make a command line utility that takes any number of numbers as arguments, and just adds them together. We’ll call it SwiftSum<\/b>.<\/p>\nA reasonable first step in building this script would be to simply print out the command line arguments. Similar to other languages, Swift automatically creates an argument count variable and argument value pointer.<\/p>\n
C_ARGC is the number of arguments passed in
\nC_ARGV is an array of the argument’s values<\/p>\nWe can loop through the arguments and print them fairly easily…<\/p>\n
\r\n#!\/usr\/bin\/env xcrun swift\r\nfor i in 1..<C_ARGC {\r\n let index = Int(i)\r\n if let argStr = String.fromCString(C_ARGV[index]) {\r\n println(argStr)\r\n }\r\n}\r\n<\/pre>\n\r\nSwiftSum.swift 1 2 3\r\n<\/pre>\nOutputs:<\/p>\n
\r\n1\r\n2\r\n3\r\n<\/pre>\nIf we want to add these, we just need to attempt converting them to an Int, and if that succeeds add it to a total…<\/p>\n
\r\n#!\/usr\/bin\/env xcrun swift\r\n\r\nvar total : Int = 0\r\n\r\nfor i in 1..<C_ARGC {\r\n let index = Int(i)\r\n if let argStr = String.fromCString(C_ARGV[index]) {\r\n if let argInt = argStr.toInt() {\r\n total += argInt\r\n }\r\n }\r\n}\r\n\r\nprintln(total)\r\n<\/pre>\n\r\n$ .\/SwiftSum.swift 1 2 3\r\n<\/pre>\nOutputs:<\/p>\n
\r\n6\r\n<\/pre>\n