Operating Swift information as scripts

It’s potential to run a Swift file straight from the command line if you happen to add a hashbang) to the start of the file. This fashion you do not have to manually compile the code utilizing the swiftc command. You’ll be able to merely give the file the executable permission flag and the system will name the Swift REPL below the hood, so our app may be evaluated mechanically. 🔨

#!/usr/bin/env swift

print("Hey, world!")

For instance this essential.swift file above may be marked as an executable file, and we are able to merely name it through the ./essential.swift command in a while (you simply have to make use of chmod just one time).

chmod +x essential.swift 
./essential.swift  
# Hey, world!

The fantastic thing about this methodology is that you could quickly check your Swift command line snippets. You’ll be able to even place the completed Swift scripts below the /usr/native/bin/ listing with out the swift file extension to make them out there “globally” on your working system person. 💪

Utilizing command line arguments in Swift

The CommandLine enum makes it very straightforward to fetch the arguments handed to our Swift utility or script. You’ll be able to entry each argument utilizing the arguments variable as an array of Strings, however it is usually potential to get the uncooked knowledge utilizing the argc and unsafeArgv properties.

#!/usr/bin/env swift


let script = CommandLine.arguments[0]
print("Script:", script)


let inputArgs = CommandLine.arguments.dropFirst()
print("Variety of arguments:", inputArgs.rely)

print("Arguments:")
for arg in inputArgs {
    print("-", arg)
}

You need to word that the primary argument is at all times the trail of the present script, so in case you are solely searching for the enter arguments you should utilize the dropFirst() methodology to return a subset of the enter strings. Normally every argument is separated by an area character.

./essential.swift howdy world
# Script: essential.swift
# Variety of arguments: 2
# Arguments:
# - howdy
# - world

In Xcode you possibly can add customized arguments below the Edit Scheme… menu merchandise whenever you click on on the present scheme, search for the Arguments tab and use the Arguments Handed On Launch part.

Course of information and surroundings in Swift Identical to we are able to entry command line arguments, it’s potential to look at the present course of together with some {hardware} data and surroundings variables.

#!/usr/bin/env swift
import Basis

let information = ProcessInfo.processInfo

print("Course of information")
print("Course of identifier:", information.processIdentifier)
print("System uptime:", information.systemUptime)
print("Globally distinctive course of id string:", information.globallyUniqueString)
print("Course of identify:", information.processName)

print("Software program information")
print("Host identify:", information.hostName)
print("OS main model:", information.operatingSystemVersion.majorVersion)
print("OS model string", information.operatingSystemVersionString)

print("{Hardware} information")
print("Energetic processor rely:", information.activeProcessorCount)
print("Bodily reminiscence (bytes)", information.physicalMemory)


print("Arguments")
print(ProcessInfo.processInfo.arguments)

print("Setting")

print(information.surroundings)

The surroundings variables property is a Dictionary the place each the keys and the values can be found as strings, so that you might need to parse them in case you are searching for totally different worth varieties. You’ll be able to arrange surroundings customized variables in Xcode identical to arguments, or you possibly can move them through the command line earlier than you execute the Swift script utilizing the export command.

Normal enter and output in Swift

You need to use the print perform to put in writing textual content to the usual output, however it’s best to word that the print perform has a variadic gadgets definition, so you possibly can move round a number of arguments and a customized separator & terminator parameter to show extra superior outputs.

There’s additionally a regular error stream, which is a part of the customary streams after all, however what’s fascinating about it’s that you could additionally write to this channel by way of the FileHandle.standardError property there may be fairly a chic resolution on a Stack Overflow thread initially created by Rob Napier, I will embrace that one right here as effectively. 🙏

One other nice characteristic of the print perform is the to parameter, which may settle for a customized TextOutputStream so you possibly can wrap the stderr stream in a customized object or you may also create customized output handlers and separate your print statements e.g. by context if you happen to want.

#!/usr/bin/env swift
import Basis


print("This", "is", "enjoyable", separator: "-", terminator: "!")


"This goes to the usual error output"
    .knowledge(utilizing: .utf8)
    .map(FileHandle.standardError.write)


last class StandardErrorOutputStream: TextOutputStream {
    func write(_ string: String) {
        FileHandle.standardError.write(Information(string.utf8))
    }
}

var outputStream = StandardErrorOutputStream()
print("That is additionally an error", to: &outputStream)



func clear() {
    print("u{1B}[2J")
    print("u{1B}[(1);(0)H", terminator: "")
}

print("foooooooooooooooooooooo")
clear()
print("Hello, world!")



print("u{1b}[31;1mu{1b}[40;1m("Hello, world!")u{1b}[m")
print("u{1b}[32;1m("Hello, world!")u{1b}[m")


print("Please enter your input:")
guard let input = readLine(strippingNewline: true) else {
    fatalError("Missing input")
}
print(input)

The second half of the snippet is full of ANSI escape codes which I like quite a lot, because it can make our terminal output quite beautiful. The only problem is that they don’t work in Xcode at all (come-on Apple, please support this…). You can clear the console or change the background / foreground color of the output by using these codes.

There are quite a lot of libraries on GitHub that you can use to print colorful output, for example ColorizeSwift, ANSITerminal, ANSIEscapeCode and many more cool ones.

The very last thing that I’d like to show you is the readLine function, which you can use to read a line from the standard input. This comes handy if you need to get user input from the command line.

Use an argument parser library

If you are looking for a type-safe argument parser written in Swift, you should definitely take a look at the Swift Argument Parser library. It is created and maintained by Apple, so it’s kind of an official solution for this particular issue, but IMHO it lacks some advanced features.

This is the main reason why I prefer the Vapor command API built on top of the ConsoleKit library. Both libraries can parse arguments, options and flags, but ConsoleKit is also capable of displaying progress indicators, it features multiple command groups, secure input, auto-completion, multiple log levels and many more.

import Foundation
import ConsoleKit

final class HelloCommand: Command {
        
    struct Signature: CommandSignature {

        @Argument(name: "name", help: "The name to say hello")
        var name: String

        @Option(name: "greeting", short: "g", help: "Greeting used")
        var greeting: String?

        @Flag(name: "capitalize", short: "c", help: "Capitalizes the name")
        var capitalize: Bool
    }

    static var name = "hello"
    let help = "This command will say hello to a given name."

    func run(using context: CommandContext, signature: Signature) throws {
        let greeting = signature.greeting ?? "Hello"
        var name = signature.name
        if signature.capitalize {
            name = name.capitalized
        }
        print("(greeting) (name)!")
        
        
        let bar = context.console.progressBar(title: "Hello")
        bar.start()
        
        bar.succeed()
        
        
        let foo = context.console.ask("What?")
        print(foo)
        
        
        let baz = context.console.ask("Secure what?", isSecure: true)
        print(baz)
        
        
        let c = context.console.choose("Make a choice", from: ["foo", "bar", "baz"])
        print(c)

        
    }
}


import Basis
import ConsoleKit

let console: Console = Terminal()
var enter = CommandInput(arguments: CommandLine.arguments)
var context = CommandContext(console: console, enter: enter)

var instructions = Instructions(enableAutocomplete: true)
instructions.use(HelloCommand(), as: HelloCommand.identify, isDefault: false)

do {
    let group = instructions.group(assist: "Utilizing ConsoleKit with out Vapor.")
    strive console.run(group, enter: enter)
}
catch {
    console.error("(error)")
    exit(1)
}

You need to use each resolution by way of the Swift Bundle Supervisor, the setup course of is kind of straightforward, you will discover extra tutorials in regards to the Swift Argument Parser and I feel that it’s tougher to search out correct docs for ConsoleKit, so yeah… anyway, they’re nice libraries you will not remorse utilizing them. 😉

Make the most of the Swift Bundle Supervisor

The Swift Bundle Supervisor is without doubt one of the neatest thing in regards to the Swift programming language. I actually find it irresistible and I take advantage of it virtually daily. The truth that the bundle manifest file is outlined utilizing Swift itself makes it straightforward to make use of & perceive.

import PackageDescription

let bundle = Bundle(
    identify: "myProject",
    platforms: [
        .macOS(.v10_15)
    ],
    dependencies: [
        .package(url: "https://github.com/vapor/console-kit", from: "4.1.0"),
    ],
    targets: [
        .executableTarget(name: "myProject",dependencies: [
            .product(name: "ConsoleKit", package: "console-kit"),
        ]),
        .testTarget(identify: "myProjectTests", dependencies: ["myProject"]),
    ]
)

The bundle supervisor developed rather a lot throughout the previous few months, if you happen to check out the Swift Evolution dashboard you possibly can monitor these adjustments, the newest replace was the introduction of customized, user-defined Bundle Collections, however in case you are searching for packages you possibly can at all times check out the Swift Bundle Index web site. 👍