Command Line Arguments in Swift

Command-line arguments are a common way to parameterize execution of programs. For example, swift run hello.swift uses run and hello.swift arguments to the swift program.

import Foundation

func main() {
    // CommandLine.arguments provides access to raw command-line
    // arguments. Note that the first value in this array
    // is the path to the program, and CommandLine.arguments[1...]
    // holds the arguments to the program.
    let argsWithProg = CommandLine.arguments
    let argsWithoutProg = Array(CommandLine.arguments.dropFirst())

    // You can get individual args with normal indexing.
    let arg = CommandLine.arguments[3]

    print(argsWithProg)
    print(argsWithoutProg)
    print(arg)
}

main()

To experiment with command-line arguments it’s best to build an executable first.

$ swiftc command-line-arguments.swift -o command-line-arguments
$ ./command-line-arguments a b c d
[./command-line-arguments, a, b, c, d]
[a, b, c, d]
c

Next we’ll look at more advanced command-line processing with argument parsing libraries.

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Command Line Arguments in Swift