How do you access command line arguments in Swift?

Question

How do you access command line arguments for a command line application in Swift?

Answer 1

You could create an argument parser by using the CommandLine.arguments Array and add any logic you like.

You can test it. Create a file arguments.swift

//Remember the first argument is the name of the executable
print("you passed \(CommandLine.arguments.count - 1) argument(s)")
print("And they are")
for argument in CommandLine.arguments {
    print(argument)
}

compile it and run it:

$ swiftc arguments.swift
$ ./arguments argument1 argument2 argument3

The issue with you building your own argument parser is taking into account all the command-line argument conventions. I would recommend using an existing Argument Parser.

You could use:

• Vapor's Console module
• TSCUtility Argument Parser used by the Swift Package manager
• The Swift Argument Parser open-sourced by Apple

I've written about how to build command-line tools on all three. You should check them out and decide what style suits you best.

If you are interested here are the links:

•  Building a CLI tool using Swift and Vapor's Console module 
• Command-line argument parsing using Swift Package Manager's TSCUtility module 
• Understanding the Swift Argument Parser and working with STDIN