swift:tldr:81805

The command "swift" refers to the Swift programming language, which is a general-purpose programming language developed by Apple Inc. It is primarily used for developing applications for iOS, macOS, watchOS, and tvOS.

When you run the "swift" command in a terminal or command prompt, it starts the Swift interactive shell or REPL (Read-Eval-Print Loop). This allows you to enter Swift code directly and have it executed immediately.

Using the Swift REPL, you can experiment with Swift code, test algorithms, evaluate expressions, and quickly prototype functionality without having to write a full program or compile your code.

For example, running the "swift" command will open a Swift REPL prompt where you can enter Swift code line by line:

$ swift
Welcome to Apple Swift version 5.3.2 (swiftlang-1200.0.45 clang-1200.0.32.28).
Type :help for assistance.
  1> print("Hello, World!")
Hello, World!
  2> let x = 5
x: Int = 5
  3> let y = x * 2
y: Int = 10

In addition to the Swift REPL, the "swift" command can also be used to compile and run Swift source code files. You can provide a Swift file as an argument to the command, and it will compile and execute the code within that file.

For example, if you have a Swift file called "main.swift", you can run it using the "swift" command like this:

$ swift main.swift

This will compile and run the code in "main.swift" without the need for an explicit build step.

Overall, the "swift" command is the entry point to interact with the Swift programming language, providing a REPL environment for interactive coding and the ability to compile and execute Swift code from standalone files.