Operating Swift information as scripts
It’s doable to run a Swift file straight from the command line in the event you add a hashbang) to the start of the file. This manner you do not have to manually compile the code utilizing the swiftc command. You may merely give the file the executable permission flag and the system will name the Swift REPL beneath the hood, so our app will be evaluated routinely. 🔨
#!/usr/bin/env swift
print("Hey, world!")For instance this important.swift file above will be marked as an executable file, and we will merely name it by way of the ./important.swift command afterward (you simply have to make use of chmod just one time).
chmod +x important.swift
./important.swift
# Hey, world!
The great thing about this methodology is that you may quickly check your Swift command line snippets. You may even place the completed Swift scripts beneath the /usr/native/bin/ listing with out the swift file extension to make them obtainable “globally” to your working system consumer. 💪
Utilizing command line arguments in Swift
The CommandLine enum makes it very simple to fetch the arguments handed to our Swift utility or script. You may entry each argument utilizing the arguments variable as an array of Strings, however additionally it is doable to get the uncooked information 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 notice 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 need to use the dropFirst() methodology to return a subset of the enter strings. Often every argument is separated by an area character.
./important.swift good day world
# Script: important.swift
# Variety of arguments: 2
# Arguments:
# - good day
# - world
In Xcode you may add customized arguments beneath the Edit Scheme… menu merchandise once you click on on the present scheme, search for the Arguments tab and use the Arguments Handed On Launch part.
Course of information and setting in Swift Identical to we will entry command line arguments, it’s doable to look at the present course of together with some {hardware} info and setting 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 title:", information.processName)
print("Software program information")
print("Host title:", 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("Surroundings")
print(information.setting)The setting 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 may arrange setting customized variables in Xcode similar to arguments, or you may go them by way of the command line earlier than you execute the Swift script utilizing the export command.
Normal enter and output in Swift
You should utilize the print perform to write down textual content to the usual output, however it is best to notice that the print perform has a variadic gadgets definition, so you may go round a number of arguments and a customized separator & terminator parameter to show extra superior outputs.
There may be additionally an ordinary error stream, which is a part of the normal streams in fact, however what’s attention-grabbing about it’s that you may additionally write to this channel by way of the FileHandle.standardError property there’s fairly a chic resolution on a Stack Overflow thread initially created by Rob Napier, I’ll embody 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 may wrap the stderr stream in a customized object or you can too create customized output handlers and separate your print statements e.g. by context in the event you want.
#!/usr/bin/env swift
import Basis
print("This", "is", "enjoyable", separator: "-", terminator: "!")
"This goes to the usual error output"
.information(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.title, 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 should utilize each resolution by way of the Swift Package deal Supervisor, the setup course of is sort of simple, you will discover extra tutorials in regards to the Swift Argument Parser and I believe that it’s tougher to seek out correct docs for ConsoleKit, so yeah… anyway, they’re nice libraries you will not remorse utilizing them. 😉
Benefit from the Swift Package deal Supervisor
The Swift Package deal Supervisor is among the smartest thing in regards to the Swift programming language. I actually find it irresistible and I exploit it nearly on daily basis. The truth that the package deal manifest file is outlined utilizing Swift itself makes it simple to make use of & perceive.
import PackageDescription
let package deal = Package deal(
title: "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(title: "myProjectTests", dependencies: ["myProject"]),
]
)The package deal supervisor advanced quite a bit throughout the previous few months, in the event you check out the Swift Evolution dashboard you may observe these adjustments, the newest replace was the introduction of customized, user-defined Package deal Collections, however in case you are searching for packages you may at all times check out the Swift Package deal Index web site. 👍
