Amazon EC2 examples using SDK for Swift

The Package.swift file.

// swift-tools-version: 5.9
//
// The swift-tools-version declares the minimum version of Swift required to
// build this package.

import PackageDescription

let package = Package(
    name: "hello-ec2",
    // Let Xcode know the minimum Apple platforms supported.
    platforms: [
        .macOS(.v13),
        .iOS(.v15)
    ],
    dependencies: [
        // Dependencies declare other packages that this package depends on.
        .package(
            url: "https://github.com/awslabs/aws-sdk-swift",
            from: "1.0.0"),
        .package(
            url: "https://github.com/apple/swift-argument-parser.git",
            branch: "main"
        )
    ],
    targets: [
        // Targets are the basic building blocks of a package, defining a module or a test suite.
        // Targets can depend on other targets in this package and products
        // from dependencies.
        .executableTarget(
            name: "hello-ec2",
            dependencies: [
                .product(name: "AWSEC2", package: "aws-sdk-swift"),
                .product(name: "ArgumentParser", package: "swift-argument-parser")
            ],
            path: "Sources")

    ]
)

The entry.swift file.

// An example that shows how to use the AWS SDK for Swift to perform a simple
// operation using Amazon Elastic Compute Cloud (EC2).
//

import ArgumentParser
import Foundation

import AWSEC2

struct ExampleCommand: ParsableCommand {
    @Option(help: "The AWS Region to run AWS API calls in.")
    var awsRegion = "us-east-1"

    @Option(
        help: ArgumentHelp("The level of logging for the Swift SDK to perform."),
        completion: .list([
            "critical",
            "debug",
            "error",
            "info",
            "notice",
            "trace",
            "warning"
        ])
    )
    var logLevel: String = "error"

    static var configuration = CommandConfiguration(
        commandName: "hello-ec2",
        abstract: """
        Demonstrates a simple operation using Amazon EC2.
        """,
        discussion: """
        An example showing how to make a call to Amazon EC2 using the AWS SDK for Swift.
        """
    )

    /// Return an array of strings giving the names of every security group
    /// the user is a member of.
    ///
    /// - Parameter ec2Client: The `EC2Client` to use when calling
    ///   `describeSecurityGroupsPaginated()`.
    ///
    /// - Returns: An array of strings giving the names of every security
    ///   group the user is a member of.
    func getSecurityGroupNames(ec2Client: EC2Client) async -> [String] {
        let pages = ec2Client.describeSecurityGroupsPaginated(
            input: DescribeSecurityGroupsInput()
        )

        var groupNames: [String] = []

        do {
            for try await page in pages {
                guard let groups = page.securityGroups else {
                    print("*** Error: No groups returned.")
                    continue
                }

                for group in groups {
                    groupNames.append(group.groupName ?? "<unknown>")
                }
            }
        } catch {
            print("*** Error: \(error.localizedDescription)")
        }

        return groupNames
    }

    /// Called by ``main()`` to run the bulk of the example.
    func runAsync() async throws {
        let ec2Config = try await EC2Client.EC2ClientConfiguration(region: awsRegion)
        let ec2Client = EC2Client(config: ec2Config)

        let groupNames = await getSecurityGroupNames(ec2Client: ec2Client)

        print("Found \(groupNames.count) security group(s):")

        for group in groupNames {
            print("    \(group)")
        }
    }
}

/// The program's asynchronous entry point.
@main
struct Main {
    static func main() async {
        let args = Array(CommandLine.arguments.dropFirst())

        do {
            let command = try ExampleCommand.parse(args)
            try await command.runAsync()
        } catch {
            ExampleCommand.exit(withError: error)
        }
    }    
}

The Package.swift file.

// swift-tools-version: 5.9
//
// The swift-tools-version declares the minimum version of Swift required to
// build this package.

import PackageDescription

let package = Package(
    name: "ec2-scenario",
    // Let Xcode know the minimum Apple platforms supported.
    platforms: [
        .macOS(.v13),
        .iOS(.v15)
    ],
    dependencies: [
        // Dependencies declare other packages that this package depends on.
        .package(
            url: "https://github.com/awslabs/aws-sdk-swift",
            from: "1.4.0"),
        .package(
            url: "https://github.com/apple/swift-argument-parser.git",
            branch: "main"
        )
    ],
    targets: [
        // Targets are the basic building blocks of a package, defining a module or a test suite.
        // Targets can depend on other targets in this package and products
        // from dependencies.
        .executableTarget(
            name: "ec2-scenario",
            dependencies: [
                .product(name: "AWSEC2", package: "aws-sdk-swift"),
                .product(name: "AWSSSM", package: "aws-sdk-swift"),
                .product(name: "ArgumentParser", package: "swift-argument-parser")
            ],
            path: "Sources")

    ]
)

The entry.swift file.

// An example that shows how to use the AWS SDK for Swift to perform a variety
// of operations using Amazon Elastic Compute Cloud (EC2).
//

import ArgumentParser
import Foundation
import AWSEC2

// Allow waiters to be used.

import class SmithyWaitersAPI.Waiter
import struct SmithyWaitersAPI.WaiterOptions

import AWSSSM

struct ExampleCommand: ParsableCommand {
    @Option(help: "The AWS Region to run AWS API calls in.")
    var awsRegion = "us-east-1"

    @Option(
        help: ArgumentHelp("The level of logging for the Swift SDK to perform."),
        completion: .list([
            "critical",
            "debug",
            "error",
            "info",
            "notice",
            "trace",
            "warning"
        ])
    )
    var logLevel: String = "error"

    static var configuration = CommandConfiguration(
        commandName: "ec2-scenario",
        abstract: """
        Performs various operations to demonstrate the use of Amazon EC2 using the
        AWS SDK for Swift.
        """,
        discussion: """
        """
    )

    /// Called by ``main()`` to run the bulk of the example.
    func runAsync() async throws {
        let ssmConfig = try await SSMClient.SSMClientConfiguration(region: awsRegion)
        let ssmClient = SSMClient(config: ssmConfig)

        let ec2Config = try await EC2Client.EC2ClientConfiguration(region: awsRegion)
        let ec2Client = EC2Client(config: ec2Config)

        let example = Example(ec2Client: ec2Client, ssmClient: ssmClient)

        await example.run()
    }
}

class Example {
    let ec2Client: EC2Client
    let ssmClient: SSMClient

    // Storage for AWS EC2 properties.

    var keyName: String? = nil
    var securityGroupId: String? = nil
    var instanceId: String? = nil
    var allocationId: String? = nil
    var associationId: String? = nil

    init(ec2Client: EC2Client, ssmClient: SSMClient) {
        self.ec2Client = ec2Client
        self.ssmClient = ssmClient
    }

    /// The example's main body.
    func run() async {
        //=====================================================================
        // 1. Create an RSA key pair, saving the private key as a `.pem` file.
        //    Create a `defer` block that will delete the private key when the
        //    program exits.
        //=====================================================================

        print("Creating an RSA key pair...")

        keyName = self.tempName(prefix: "ExampleKeyName")
        let keyUrl = await self.createKeyPair(name: keyName!)

        guard let keyUrl else {
            print("*** Failed to create the key pair!")
            return
        }

        print("Created the private key at: \(keyUrl.absoluteString)")

        // Schedule deleting the private key file to occur automatically when
        // the program exits, no matter how it exits.

        defer {
            do {
                try FileManager.default.removeItem(at: keyUrl)
            } catch {
                print("*** Failed to delete the private key at \(keyUrl.absoluteString)")
            }
        }

        //=====================================================================
        // 2. List the key pairs by calling `DescribeKeyPairs`.
        //=====================================================================

        print("Describing available key pairs...")
        await self.describeKeyPairs()

        //=====================================================================
        // 3. Create a security group for the default VPC, and add an inbound
        //    rule to allow SSH from the current computer's public IPv4
        //    address.
        //=====================================================================

        print("Creating the security group...")

        let secGroupName = self.tempName(prefix: "ExampleSecurityGroup")
        let ipAddress = self.getMyIPAddress()

        guard let ipAddress else {
            print("*** Unable to get the device's IP address.")
            return
        }

        print("IP address is: \(ipAddress)")

        securityGroupId = await self.createSecurityGroup(
            name: secGroupName,
            description: "An example security group created using the AWS SDK for Swift"
        )

        if securityGroupId == nil {
            await cleanUp()
            return
        }

        print("Created security group: \(securityGroupId ?? "<unknown>")")

        if !(await self.authorizeSecurityGroupIngress(groupId: securityGroupId!, ipAddress: ipAddress)) {
            await cleanUp()
            return
        }

        //=====================================================================
        // 4. Display security group information for the new security group
        //    using DescribeSecurityGroups.
        //=====================================================================

        if !(await self.describeSecurityGroups(groupId: securityGroupId!)) {
            await cleanUp()
            return
        }

        //=====================================================================
        // 5. Get a list of Amazon Linux 2023 AMIs and pick one (SSM is the
        //    best practice), using path and then filter the list after the
        //    fact to include "al2023" in the Name field
        //    (ssm.GetParametersByPath). Paginate to get all images.
        //=====================================================================

        print("Searching available images for Amazon Linux 2023 images...")

        let options = await self.findAMIsMatchingFilter("al2023")

        //=====================================================================
        // 6. The information in the AMI options isn't great, so make a list
        //    of the image IDs (the "Value" field in the AMI options) and get
        //    more information about them from EC2. Display the Description
        //    field and select one of them (DescribeImages with ImageIds
        //    filter).
        //=====================================================================

        print("Images matching Amazon Linux 2023:")

        var imageIds: [String] = []
        for option in options {
            guard let id = option.value else {
                continue
            }
            imageIds.append(id)
        }
        
        let images = await self.describeImages(imageIds)

        // This is where you would normally let the user choose which AMI to
        // use. However, for this example, we're just going to use the first
        // one, whatever it is.

        let chosenImage = images[0]

        //=====================================================================
        // 7. Get a list of instance types that are compatible with the
        //    selected AMI's architecture (such as "x86_64") and are either
        //    small or micro. Select one (DescribeInstanceTypes).
        //=====================================================================

        print("Getting the instance types compatible with the selected image...")

        guard let arch = chosenImage.architecture else {
            print("*** The selected image doesn't have a valid architecture.")
            await cleanUp()
            return
        }

        let imageTypes = await self.getMatchingInstanceTypes(architecture: arch)

        for type in imageTypes {
            guard let instanceType = type.instanceType else {
                continue
            }
            print("    \(instanceType.rawValue)")
        }

        // This example selects the first returned instance type. A real-world
        // application would probably ask the user to select one here.

        let chosenInstanceType = imageTypes[0]

        //=====================================================================
        // 8. Create an instance with the key pair, security group, AMI, and
        //    instance type (RunInstances).
        //=====================================================================

        print("Creating an instance...")

        guard let imageId = chosenImage.imageId else {
            print("*** Cannot start image without a valid image ID.")
            await cleanUp()
            return
        }
        guard let instanceType = chosenInstanceType.instanceType else {
            print("*** Unable to start image without a valid image type.")
            await cleanUp()
            return
        }

        let instance = await self.runInstance(
            imageId: imageId,
            instanceType: instanceType,
            keyPairName: keyName!,
            securityGroups: [securityGroupId!]
        )

        guard let instance else {
            await cleanUp()
            return
        }

        instanceId = instance.instanceId
        if instanceId == nil {
            print("*** Instance is missing an ID. Canceling.")
            await cleanUp()
            return
        }

        //=====================================================================
        // 9. Wait for the instance to be ready and then display its
        //    information (DescribeInstances).
        //=====================================================================

        print("Waiting a few seconds to let the instance come up...")
        
        do {
            try await Task.sleep(for: .seconds(20))
        } catch {
            print("*** Error pausing the task.")
        }
        print("Success! Your new instance is ready:")

        //=====================================================================
        // 10. Display SSH connection info for the instance.
        //=====================================================================

        var runningInstance = await self.describeInstance(instanceId: instanceId!)

        if (runningInstance != nil) && (runningInstance!.publicIpAddress != nil) {
            print("\nYou can SSH to this instance using the following command:")
            print("ssh -i \(keyUrl.path) ec2-user@\(runningInstance!.publicIpAddress!)")
        }

        //=====================================================================
        // 11. Stop the instance and wait for it to stop (StopInstances).
        //=====================================================================

        print("Stopping the instance...")

        if !(await self.stopInstance(instanceId: instanceId!, waitUntilStopped: true)) {
            await cleanUp()
            return
        }

        //=====================================================================
        // 12. Start the instance and wait for it to start (StartInstances).
        //=====================================================================

        print("Starting the instance again...")

        if !(await self.startInstance(instanceId: instanceId!, waitUntilStarted: true)) {
            await cleanUp()
            return
        }

        //=====================================================================
        // 13. Display SSH connection info for the instance. Note that it's
        //     changed.
        //=====================================================================

        runningInstance = await self.describeInstance(instanceId: instanceId!)
        if (runningInstance != nil) && (runningInstance!.publicIpAddress != nil) {
            print("\nYou can SSH to this instance using the following command.")
            print("This is probably different from when the instance was running before.")
            print("ssh -i \(keyUrl.path) ec2-user@\(runningInstance!.publicIpAddress!)")
        }

        //=====================================================================
        // 14. Allocate an elastic IP and associate it with the instance
        //     (AllocateAddress and AssociateAddress).
        //=====================================================================

        allocationId = await self.allocateAddress()

        if allocationId == nil {
            await cleanUp()
            return
        }

        associationId = await self.associateAddress(instanceId: instanceId!, allocationId: allocationId)

        if associationId == nil {
            await cleanUp()
            return
        }

        //=====================================================================
        // 15. Display SSH connection info for the connection. Note that the
        //     public IP is now the Elastic IP, which stays constant.
        //=====================================================================

        runningInstance = await self.describeInstance(instanceId: instanceId!)
        if (runningInstance != nil) && (runningInstance!.publicIpAddress != nil) {
            print("\nYou can SSH to this instance using the following command.")
            print("This has changed again, and is now the Elastic IP.")
            print("ssh -i \(keyUrl.path) ec2-user@\(runningInstance!.publicIpAddress!)")
        }

        //=====================================================================
        // Handle all cleanup tasks
        //=====================================================================

        await cleanUp()
    }

    /// Clean up by discarding and closing down all allocated EC2 items:
    /// 
    /// * Elastic IP allocation and association
    /// * Terminate the instance
    /// * Delete the security group
    /// * Delete the key pair
    func cleanUp() async {
        //=====================================================================
        // 16. Disassociate and delete the Elastic IP (DisassociateAddress and
        //     ReleaseAddress).
        //=====================================================================

        if associationId != nil {
            await self.disassociateAddress(associationId: associationId!)
        }

        if allocationId != nil {
            await self.releaseAddress(allocationId: allocationId!)
        }

        //=====================================================================
        // 17. Terminate the instance and wait for it to terminate
        //     (TerminateInstances).
        //=====================================================================

        if instanceId != nil {
            print("Terminating the instance...")
            _ = await self.terminateInstance(instanceId: instanceId!, waitUntilTerminated: true)
        }

        //=====================================================================
        // 18. Delete the security group (DeleteSecurityGroup).
        //=====================================================================

        if securityGroupId != nil {
            print("Deleting the security group...")
            _ = await self.deleteSecurityGroup(groupId: securityGroupId!)
        }

        //=====================================================================
        // 19. Delete the key pair (DeleteKeyPair).
        //=====================================================================

        if keyName != nil {
            print("Deleting the key pair...")
            _ = await self.deleteKeyPair(keyPair: keyName!)
        }
    }

    /// Create a new RSA key pair and save the private key to a randomly-named
    /// file in the temporary directory.
    ///
    /// - Parameter name: The name of the key pair to create.
    ///
    /// - Returns: The URL of the newly created `.pem` file or `nil` if unable
    ///   to create the key pair.
    func createKeyPair(name: String) async -> URL? {
        do {
            let output = try await ec2Client.createKeyPair(
                input: CreateKeyPairInput(
                    keyName: name
                )
            )

            guard let keyMaterial = output.keyMaterial else {
                return nil
            }

            // Build the URL of the temporary private key file.

            let fileURL = URL.temporaryDirectory
                                  .appendingPathComponent(name)
                                  .appendingPathExtension("pem")

            do {
                try keyMaterial.write(to: fileURL, atomically: true, encoding: String.Encoding.utf8)
                return fileURL
            } catch {
                print("*** Failed to write the private key.")
                return nil
            }
        } catch {
            print("*** Unable to create the key pair.")
            return nil
        }
    }

    /// Describe the key pairs associated with the user by outputting each key
    /// pair's name and fingerprint.
    func describeKeyPairs() async {
        do {
            let output = try await ec2Client.describeKeyPairs(
                input: DescribeKeyPairsInput()
            )

            guard let keyPairs = output.keyPairs else {
                print("*** No key pairs list available.")
                return
            }

            for keyPair in keyPairs {
                print(keyPair.keyName ?? "<unknown>", ":", keyPair.keyFingerprint ?? "<unknown>")
            }
        } catch {
            print("*** Error: Unable to obtain a key pair list.")
        }
    }

    /// Delete an EC2 key pair.
    /// 
    /// - Parameter keyPair: The name of the key pair to delete.
    /// 
    /// - Returns: `true` if the key pair is deleted successfully; otherwise
    ///   `false`.
    func deleteKeyPair(keyPair: String) async -> Bool {
        do {
            _ = try await ec2Client.deleteKeyPair(
                input: DeleteKeyPairInput(
                    keyName: keyPair
                )
            )

            return true
        } catch {
            print("*** Error deleting the key pair: \(error.localizedDescription)")
            return false
        }
    }

    /// Return a list of AMI names that contain the specified string.
    /// 
    /// - Parameter filter: A string that must be contained in all returned
    ///   AMI names.
    ///
    /// - Returns: An array of the parameters matching the specified substring.
    func findAMIsMatchingFilter(_ filter: String) async -> [SSMClientTypes.Parameter] {
        var parameterList: [SSMClientTypes.Parameter] = []
        var matchingAMIs: [SSMClientTypes.Parameter] = []

        do {
            let pages = ssmClient.getParametersByPathPaginated(
                input: GetParametersByPathInput(
                    path: "/aws/service/ami-amazon-linux-latest"
                )
            )

            for try await page in pages {
                guard let parameters = page.parameters else {
                    return matchingAMIs
                }

                for parameter in parameters {
                    parameterList.append(parameter)
                }
            }

            print("Found \(parameterList.count) images total:")
            for parameter in parameterList {
                guard let name = parameter.name else {
                    continue
                }
                print("    \(name)")

                if name.contains(filter) {
                    matchingAMIs.append(parameter)
                }
            }
        } catch {
            return matchingAMIs
        }

        return matchingAMIs
    }

    /// Return a list of instance types matching the specified architecture
    /// and instance sizes.
    /// 
    /// - Parameters:
    ///   - architecture: The architecture of the instance types to return, as
    ///     a member of `EC2ClientTypes.ArchitectureValues`.
    ///   - sizes: An array of one or more strings identifying sizes of
    ///     instance type to accept.
    /// 
    /// - Returns: An array of `EC2ClientTypes.InstanceTypeInfo` records
    ///   describing the instance types matching the given requirements.
    func getMatchingInstanceTypes(architecture: EC2ClientTypes.ArchitectureValues = EC2ClientTypes.ArchitectureValues.x8664,
                          sizes: [String] = ["*.micro", "*.small"]) async
                          -> [EC2ClientTypes.InstanceTypeInfo] {
        var instanceTypes: [EC2ClientTypes.InstanceTypeInfo] = []    

        let archFilter = EC2ClientTypes.Filter(
            name: "processor-info.supported-architecture",
            values: [architecture.rawValue]
        )
        let sizeFilter = EC2ClientTypes.Filter(
            name: "instance-type",
            values: sizes
        )

        do {
            let pages = ec2Client.describeInstanceTypesPaginated(
                input: DescribeInstanceTypesInput(
                    filters: [archFilter, sizeFilter]
                )
            )

            for try await page in pages {
                guard let types = page.instanceTypes else {
                    return []
                }

                instanceTypes += types
            }
        } catch {
            print("*** Error getting image types: \(error.localizedDescription)")
            return []
        }

        return instanceTypes
    }

    /// Get the latest information about the specified instance and output it
    /// to the screen, returning the instance details to the caller.
    /// 
    /// - Parameters:
    ///   - instanceId: The ID of the instance to provide details about.
    ///   - stateFilter: The state to require the instance to be in.
    ///
    /// - Returns: The instance's details as an `EC2ClientTypes.Instance` object.
    func describeInstance(instanceId: String,
                          stateFilter: EC2ClientTypes.InstanceStateName? = EC2ClientTypes.InstanceStateName.running) async
                          -> EC2ClientTypes.Instance? {
        do {
            let pages = ec2Client.describeInstancesPaginated(
                input: DescribeInstancesInput(
                    instanceIds: [instanceId]
                )
            )

            for try await page in pages {
                guard let reservations = page.reservations else {
                    continue
                }

                for reservation in reservations {
                    guard let instances = reservation.instances else {
                        continue
                    }

                    for instance in instances {
                        guard let state = instance.state else {
                            print("*** Instance is missing its state...")
                            continue
                        }
                        let instanceState = state.name

                        if stateFilter != nil && (instanceState != stateFilter) {
                            continue
                        }

                        let instanceTypeName: String
                        if instance.instanceType == nil {
                            instanceTypeName = "<N/A>"
                        } else {
                            instanceTypeName = instance.instanceType?.rawValue ?? "<N/A>"
                        }

                        let instanceStateName: String
                        if instanceState == nil {
                            instanceStateName = "<N/A>"
                        } else {
                            instanceStateName = instanceState?.rawValue ?? "<N/A>"
                        }

                        print("""
                        Instance: \(instance.instanceId ?? "<N/A>")
                                • Image ID: \(instance.imageId ?? "<N/A>")
                                • Instance type: \(instanceTypeName)
                                • Key name: \(instance.keyName ?? "<N/A>")
                                • VPC ID: \(instance.vpcId ?? "<N/A>")
                                • Public IP: \(instance.publicIpAddress ?? "N/A")
                                • State: \(instanceStateName)
                        """)

                        return instance
                    }
                }
            }
        } catch {
            print("*** Error retrieving instance information to display: \(error.localizedDescription)")
            return nil
        }

        return nil
    }

    /// Stop the specified instance.
    /// 
    /// - Parameters:
    ///   - instanceId: The ID of the instance to stop.
    ///   - waitUntilStopped: If `true`, execution waits until the instance
    ///     has stopped. Otherwise, execution continues and the instance stops
    ///     asynchronously.
    ///
    /// - Returns: `true` if the image is successfully stopped (or is left to
    ///   stop asynchronously). `false` if the instance doesn't stop.
    func stopInstance(instanceId: String, waitUntilStopped: Bool = false) async -> Bool {
        let instanceList = [instanceId]

        do {
            _ = try await ec2Client.stopInstances(
                input: StopInstancesInput(
                    instanceIds: instanceList
                )
            )

            if waitUntilStopped {
                print("Waiting for the instance to stop. Please be patient!")

                let waitOptions = WaiterOptions(maxWaitTime: 600)
                let output = try await ec2Client.waitUntilInstanceStopped(
                    options: waitOptions,
                    input: DescribeInstancesInput(
                        instanceIds: instanceList
                    )
                )

                switch output.result {
                case .success:
                    return true
                case .failure:
                    return false
                }
            } else {
                return true
            }
        } catch {
            print("*** Unable to stop the instance: \(error.localizedDescription)")
            return false
        }
    }

    /// Start the specified instance.
    /// 
    /// - Parameters:
    ///   - instanceId: The ID of the instance to start.
    ///   - waitUntilStarted: If `true`, execution waits until the instance
    ///     has started. Otherwise, execution continues and the instance starts
    ///     asynchronously.
    ///
    /// - Returns: `true` if the image is successfully started (or is left to
    ///   start asynchronously). `false` if the instance doesn't start.
    func startInstance(instanceId: String, waitUntilStarted: Bool = false) async -> Bool {
        let instanceList = [instanceId]

        do {
            _ = try await ec2Client.startInstances(
                input: StartInstancesInput(
                    instanceIds: instanceList
                )
            )

            if waitUntilStarted {
                print("Waiting for the instance to start...")

                let waitOptions = WaiterOptions(maxWaitTime: 60.0)
                let output = try await ec2Client.waitUntilInstanceRunning(
                    options: waitOptions,
                    input: DescribeInstancesInput(
                        instanceIds: instanceList
                    )
                )
                switch output.result {
                case .success:
                    return true
                case .failure:
                    return false
                }
            } else {
                return true
            }
        } catch {
            print("*** Unable to start the instance: \(error.localizedDescription)")
            return false
        }
    }

    /// Terminate the specified instance.
    ///
    /// - Parameters:
    ///   - instanceId: The instance to terminate.
    ///   - waitUntilTerminated: Whether or not to wait until the instance is
    ///     terminated before returning.
    /// 
    /// - Returns: `true` if terminated successfully. `false` if not or if an
    ///   error occurs.
    func terminateInstance(instanceId: String, waitUntilTerminated: Bool = false) async -> Bool {
        let instanceList = [instanceId]

        do {
            _ = try await ec2Client.terminateInstances(
                input: TerminateInstancesInput(
                    instanceIds: instanceList
                )
            )

            if waitUntilTerminated {
                print("Waiting for the instance to terminate...")

                let waitOptions = WaiterOptions(maxWaitTime: 600.0)
                let output = try await ec2Client.waitUntilInstanceTerminated(
                    options: waitOptions,
                    input: DescribeInstancesInput(
                        instanceIds: instanceList
                    )
                )

                switch output.result {
                case .success:
                    return true
                case .failure:
                    return false
                }
            } else {
                return true
            }
        } catch {
            print("*** Unable to terminate the instance: \(error.localizedDescription)")
            return false
        }
    }

    /// Return an array of `EC2ClientTypes.Image` objects describing all of
    /// the images in the specified array.
    /// 
    /// - Parameter idList: A list of image ID strings indicating the images
    ///   to return details about.
    ///
    /// - Returns: An array of the images.
    func describeImages(_ idList: [String]) async -> [EC2ClientTypes.Image] {
        do {
            let output = try await ec2Client.describeImages(
                input: DescribeImagesInput(
                    imageIds: idList
                )
            )

            guard let images = output.images else {
                print("*** No images found.")
                return []
            }

            for image in images {
                guard let id = image.imageId else {
                    continue
                }
                print("   \(id): \(image.description ?? "<no description>")")
            }

            return images
        } catch {
            print("*** Error getting image descriptions: \(error.localizedDescription)")
            return []
        }
    }

    /// Create and return a new EC2 instance.
    /// 
    /// - Parameters:
    ///   - imageId: The image ID of the AMI to use when creating the instance.
    ///   - instanceType: The type of instance to create.
    ///   - keyPairName: The RSA key pair's name to use to secure the instance.
    ///   - securityGroups: The security group or groups to add the instance
    ///     to.
    ///
    /// - Returns: The EC2 instance as an `EC2ClientTypes.Instance` object.
    func runInstance(imageId: String, instanceType: EC2ClientTypes.InstanceType,
                        keyPairName: String, securityGroups: [String]?) async -> EC2ClientTypes.Instance? {
        do {
            let output = try await ec2Client.runInstances(
                input: RunInstancesInput(
                    imageId: imageId,
                    instanceType: instanceType,
                    keyName: keyPairName,
                    maxCount: 1,
                    minCount: 1,
                    securityGroupIds: securityGroups
                )
            )

            guard let instances = output.instances else {
                print("*** Unable to create the instance.")
                return nil
            }

            return instances[0]
        } catch {
            print("*** Error creating the instance: \(error.localizedDescription)")
            return nil
        }
    }

    /// Return the device's external IP address.
    /// 
    /// - Returns: A string containing the device's IP address.
    func getMyIPAddress() -> String? {
        guard let url = URL(string: "http://checkip.amazonaws.com") else {
            print("Couldn't create the URL")
            return nil
        }

        do {
            print("Getting the IP address...")
            return try String(contentsOf: url, encoding: String.Encoding.utf8).trim()
        } catch {
            print("*** Unable to get your public IP address.")
            return nil
        }
    }

    /// Create a new security group.
    /// 
    /// - Parameters:
    ///   - groupName: The name of the group to create.
    ///   - groupDescription: A description of the new security group.
    ///
    /// - Returns: The ID string of the new security group.
    func createSecurityGroup(name groupName: String, description groupDescription: String) async -> String? {
        do {
            let output = try await ec2Client.createSecurityGroup(
                input: CreateSecurityGroupInput(
                    description: groupDescription,
                    groupName: groupName
                )
            )

            return output.groupId
        } catch {
            print("*** Error creating the security group: \(error.localizedDescription)")
            return nil
        }
    }

    /// Authorize ingress of connections for the security group.
    /// 
    /// - Parameters:
    ///   - groupId: The group ID of the security group to authorize access for.
    ///   - ipAddress: The IP address of the device to grant access to.
    ///
    /// - Returns: `true` if access is successfully granted; otherwise `false`.
    func authorizeSecurityGroupIngress(groupId: String, ipAddress: String) async -> Bool {
        let ipRange = EC2ClientTypes.IpRange(cidrIp: "\(ipAddress)/0")
        let httpPermission = EC2ClientTypes.IpPermission(
            fromPort: 80,
            ipProtocol: "tcp",
            ipRanges: [ipRange],
            toPort: 80
        )

        let sshPermission = EC2ClientTypes.IpPermission(
            fromPort: 22,
            ipProtocol: "tcp",
            ipRanges: [ipRange],
            toPort: 22
        )

        do {
            _ = try await ec2Client.authorizeSecurityGroupIngress(
                input: AuthorizeSecurityGroupIngressInput(
                    groupId: groupId,
                    ipPermissions: [httpPermission, sshPermission]
                )
            )

            return true
        } catch {
            print("*** Error authorizing ingress for the security group: \(error.localizedDescription)")
            return false
        }
    }

    func describeSecurityGroups(groupId: String) async -> Bool {
        do {
            let output = try await ec2Client.describeSecurityGroups(
                input: DescribeSecurityGroupsInput(
                    groupIds: [groupId]
                )
            )

            guard let securityGroups = output.securityGroups else {
                print("No security groups found.")
                return true
            }

            for group in securityGroups {
                print("Group \(group.groupId ?? "<unknown>") found with VPC \(group.vpcId ?? "<unknown>")")
            }
            return true
        } catch {
            print("*** Error getting security group details: \(error.localizedDescription)")
            return false
        }
    }

    /// Delete a security group.
    /// 
    /// - Parameter groupId: The ID of the security group to delete.
    /// 
    /// - Returns: `true` on successful deletion; `false` on error.
    func deleteSecurityGroup(groupId: String) async -> Bool {
        do {
            _ = try await ec2Client.deleteSecurityGroup(
                input: DeleteSecurityGroupInput(
                    groupId: groupId
                )
            )

            return true
        } catch {
            print("*** Error deleting the security group: \(error.localizedDescription)")
            return false
        }
    }

    /// Allocate an Elastic IP address.
    ///
    /// - Returns: A string containing the ID of the Elastic IP.
    func allocateAddress() async -> String? {
        do {
            let output = try await ec2Client.allocateAddress(
                input: AllocateAddressInput(
                    domain: EC2ClientTypes.DomainType.vpc
                )
            )

            guard let allocationId = output.allocationId else {
                return nil
            }

            return allocationId
        } catch {
            print("*** Unable to allocate the IP address: \(error.localizedDescription)")
            return nil
        }
    }

    /// Associate the specified allocated Elastic IP to a given instance.
    /// 
    /// - Parameters:
    ///   - instanceId: The instance to associate the Elastic IP with.
    ///   - allocationId: The ID of the allocated Elastic IP to associate with
    ///     the instance.
    ///
    /// - Returns: The association ID of the association.
    func associateAddress(instanceId: String?, allocationId: String?) async -> String? {
        do {
            let output = try await ec2Client.associateAddress(
                input: AssociateAddressInput(
                    allocationId: allocationId,
                    instanceId: instanceId
                )
            )

            return output.associationId
        } catch {
            print("*** Unable to associate the IP address: \(error.localizedDescription)")
            return nil
        }
    }

    /// Disassociate an Elastic IP.
    /// 
    /// - Parameter associationId: The ID of the association to end.
    func disassociateAddress(associationId: String?) async {
        do {
            _ = try await ec2Client.disassociateAddress(
                input: DisassociateAddressInput(
                    associationId: associationId
                )
            )
        } catch {
            print("*** Unable to disassociate the IP address: \(error.localizedDescription)")
        }
    }

    /// Release an allocated Elastic IP.
    /// 
    /// - Parameter allocationId: The allocation ID of the Elastic IP to
    ///   release.
    func releaseAddress(allocationId: String?) async {
        do {
            _ = try await ec2Client.releaseAddress(
                input: ReleaseAddressInput(
                    allocationId: allocationId
                )
            )
        } catch {
            print("*** Unable to release the IP address: \(error.localizedDescription)")
        }
    }

    /// Generate and return a unique file name that begins with the specified
    /// string.
    ///
    /// - Parameters:
    ///   - prefix: Text to use at the beginning of the returned name.
    ///
    /// - Returns: A string containing a unique filename that begins with the
    ///   specified `prefix`.
    ///
    /// The returned name uses a random number between 1 million and 1 billion to
    /// provide reasonable certainty of uniqueness for the purposes of this
    /// example.
    func tempName(prefix: String) -> String {
        return "\(prefix)-\(Int.random(in: 1000000..<1000000000))"
    }
}

/// The program's asynchronous entry point.
@main
struct Main {
    static func main() async {
        let args = Array(CommandLine.arguments.dropFirst())

        do {
            let command = try ExampleCommand.parse(args)
            try await command.runAsync()
        } catch {
            ExampleCommand.exit(withError: error)
        }
    }    
}

import AWSEC2

    /// Allocate an Elastic IP address.
    ///
    /// - Returns: A string containing the ID of the Elastic IP.
    func allocateAddress() async -> String? {
        do {
            let output = try await ec2Client.allocateAddress(
                input: AllocateAddressInput(
                    domain: EC2ClientTypes.DomainType.vpc
                )
            )

            guard let allocationId = output.allocationId else {
                return nil
            }

            return allocationId
        } catch {
            print("*** Unable to allocate the IP address: \(error.localizedDescription)")
            return nil
        }
    }

import AWSEC2

    /// Associate the specified allocated Elastic IP to a given instance.
    /// 
    /// - Parameters:
    ///   - instanceId: The instance to associate the Elastic IP with.
    ///   - allocationId: The ID of the allocated Elastic IP to associate with
    ///     the instance.
    ///
    /// - Returns: The association ID of the association.
    func associateAddress(instanceId: String?, allocationId: String?) async -> String? {
        do {
            let output = try await ec2Client.associateAddress(
                input: AssociateAddressInput(
                    allocationId: allocationId,
                    instanceId: instanceId
                )
            )

            return output.associationId
        } catch {
            print("*** Unable to associate the IP address: \(error.localizedDescription)")
            return nil
        }
    }

import AWSEC2

    /// Authorize ingress of connections for the security group.
    /// 
    /// - Parameters:
    ///   - groupId: The group ID of the security group to authorize access for.
    ///   - ipAddress: The IP address of the device to grant access to.
    ///
    /// - Returns: `true` if access is successfully granted; otherwise `false`.
    func authorizeSecurityGroupIngress(groupId: String, ipAddress: String) async -> Bool {
        let ipRange = EC2ClientTypes.IpRange(cidrIp: "\(ipAddress)/0")
        let httpPermission = EC2ClientTypes.IpPermission(
            fromPort: 80,
            ipProtocol: "tcp",
            ipRanges: [ipRange],
            toPort: 80
        )

        let sshPermission = EC2ClientTypes.IpPermission(
            fromPort: 22,
            ipProtocol: "tcp",
            ipRanges: [ipRange],
            toPort: 22
        )

        do {
            _ = try await ec2Client.authorizeSecurityGroupIngress(
                input: AuthorizeSecurityGroupIngressInput(
                    groupId: groupId,
                    ipPermissions: [httpPermission, sshPermission]
                )
            )

            return true
        } catch {
            print("*** Error authorizing ingress for the security group: \(error.localizedDescription)")
            return false
        }
    }

import AWSEC2

    /// Create a new RSA key pair and save the private key to a randomly-named
    /// file in the temporary directory.
    ///
    /// - Parameter name: The name of the key pair to create.
    ///
    /// - Returns: The URL of the newly created `.pem` file or `nil` if unable
    ///   to create the key pair.
    func createKeyPair(name: String) async -> URL? {
        do {
            let output = try await ec2Client.createKeyPair(
                input: CreateKeyPairInput(
                    keyName: name
                )
            )

            guard let keyMaterial = output.keyMaterial else {
                return nil
            }

            // Build the URL of the temporary private key file.

            let fileURL = URL.temporaryDirectory
                                  .appendingPathComponent(name)
                                  .appendingPathExtension("pem")

            do {
                try keyMaterial.write(to: fileURL, atomically: true, encoding: String.Encoding.utf8)
                return fileURL
            } catch {
                print("*** Failed to write the private key.")
                return nil
            }
        } catch {
            print("*** Unable to create the key pair.")
            return nil
        }
    }

import AWSEC2

    /// Create a new security group.
    /// 
    /// - Parameters:
    ///   - groupName: The name of the group to create.
    ///   - groupDescription: A description of the new security group.
    ///
    /// - Returns: The ID string of the new security group.
    func createSecurityGroup(name groupName: String, description groupDescription: String) async -> String? {
        do {
            let output = try await ec2Client.createSecurityGroup(
                input: CreateSecurityGroupInput(
                    description: groupDescription,
                    groupName: groupName
                )
            )

            return output.groupId
        } catch {
            print("*** Error creating the security group: \(error.localizedDescription)")
            return nil
        }
    }

import AWSEC2

    /// Delete an EC2 key pair.
    /// 
    /// - Parameter keyPair: The name of the key pair to delete.
    /// 
    /// - Returns: `true` if the key pair is deleted successfully; otherwise
    ///   `false`.
    func deleteKeyPair(keyPair: String) async -> Bool {
        do {
            _ = try await ec2Client.deleteKeyPair(
                input: DeleteKeyPairInput(
                    keyName: keyPair
                )
            )

            return true
        } catch {
            print("*** Error deleting the key pair: \(error.localizedDescription)")
            return false
        }
    }

import AWSEC2

    /// Delete a security group.
    /// 
    /// - Parameter groupId: The ID of the security group to delete.
    /// 
    /// - Returns: `true` on successful deletion; `false` on error.
    func deleteSecurityGroup(groupId: String) async -> Bool {
        do {
            _ = try await ec2Client.deleteSecurityGroup(
                input: DeleteSecurityGroupInput(
                    groupId: groupId
                )
            )

            return true
        } catch {
            print("*** Error deleting the security group: \(error.localizedDescription)")
            return false
        }
    }

import AWSEC2

    /// Return an array of `EC2ClientTypes.Image` objects describing all of
    /// the images in the specified array.
    /// 
    /// - Parameter idList: A list of image ID strings indicating the images
    ///   to return details about.
    ///
    /// - Returns: An array of the images.
    func describeImages(_ idList: [String]) async -> [EC2ClientTypes.Image] {
        do {
            let output = try await ec2Client.describeImages(
                input: DescribeImagesInput(
                    imageIds: idList
                )
            )

            guard let images = output.images else {
                print("*** No images found.")
                return []
            }

            for image in images {
                guard let id = image.imageId else {
                    continue
                }
                print("   \(id): \(image.description ?? "<no description>")")
            }

            return images
        } catch {
            print("*** Error getting image descriptions: \(error.localizedDescription)")
            return []
        }
    }

import AWSEC2

    /// Return a list of instance types matching the specified architecture
    /// and instance sizes.
    /// 
    /// - Parameters:
    ///   - architecture: The architecture of the instance types to return, as
    ///     a member of `EC2ClientTypes.ArchitectureValues`.
    ///   - sizes: An array of one or more strings identifying sizes of
    ///     instance type to accept.
    /// 
    /// - Returns: An array of `EC2ClientTypes.InstanceTypeInfo` records
    ///   describing the instance types matching the given requirements.
    func getMatchingInstanceTypes(architecture: EC2ClientTypes.ArchitectureValues = EC2ClientTypes.ArchitectureValues.x8664,
                          sizes: [String] = ["*.micro", "*.small"]) async
                          -> [EC2ClientTypes.InstanceTypeInfo] {
        var instanceTypes: [EC2ClientTypes.InstanceTypeInfo] = []    

        let archFilter = EC2ClientTypes.Filter(
            name: "processor-info.supported-architecture",
            values: [architecture.rawValue]
        )
        let sizeFilter = EC2ClientTypes.Filter(
            name: "instance-type",
            values: sizes
        )

        do {
            let pages = ec2Client.describeInstanceTypesPaginated(
                input: DescribeInstanceTypesInput(
                    filters: [archFilter, sizeFilter]
                )
            )

            for try await page in pages {
                guard let types = page.instanceTypes else {
                    return []
                }

                instanceTypes += types
            }
        } catch {
            print("*** Error getting image types: \(error.localizedDescription)")
            return []
        }

        return instanceTypes
    }

import AWSEC2

    /// Describe the key pairs associated with the user by outputting each key
    /// pair's name and fingerprint.
    func describeKeyPairs() async {
        do {
            let output = try await ec2Client.describeKeyPairs(
                input: DescribeKeyPairsInput()
            )

            guard let keyPairs = output.keyPairs else {
                print("*** No key pairs list available.")
                return
            }

            for keyPair in keyPairs {
                print(keyPair.keyName ?? "<unknown>", ":", keyPair.keyFingerprint ?? "<unknown>")
            }
        } catch {
            print("*** Error: Unable to obtain a key pair list.")
        }
    }

Using pagination with describeSecurityGroupsPaginated().

import AWSEC2

    /// Return an array of strings giving the names of every security group
    /// the user is a member of.
    ///
    /// - Parameter ec2Client: The `EC2Client` to use when calling
    ///   `describeSecurityGroupsPaginated()`.
    ///
    /// - Returns: An array of strings giving the names of every security
    ///   group the user is a member of.
    func getSecurityGroupNames(ec2Client: EC2Client) async -> [String] {
        let pages = ec2Client.describeSecurityGroupsPaginated(
            input: DescribeSecurityGroupsInput()
        )

        var groupNames: [String] = []

        do {
            for try await page in pages {
                guard let groups = page.securityGroups else {
                    print("*** Error: No groups returned.")
                    continue
                }

                for group in groups {
                    groupNames.append(group.groupName ?? "<unknown>")
                }
            }
        } catch {
            print("*** Error: \(error.localizedDescription)")
        }

        return groupNames
    }

Without pagination.

import AWSEC2

    func describeSecurityGroups(groupId: String) async -> Bool {
        do {
            let output = try await ec2Client.describeSecurityGroups(
                input: DescribeSecurityGroupsInput(
                    groupIds: [groupId]
                )
            )

            guard let securityGroups = output.securityGroups else {
                print("No security groups found.")
                return true
            }

            for group in securityGroups {
                print("Group \(group.groupId ?? "<unknown>") found with VPC \(group.vpcId ?? "<unknown>")")
            }
            return true
        } catch {
            print("*** Error getting security group details: \(error.localizedDescription)")
            return false
        }
    }

import AWSEC2

    /// Disassociate an Elastic IP.
    /// 
    /// - Parameter associationId: The ID of the association to end.
    func disassociateAddress(associationId: String?) async {
        do {
            _ = try await ec2Client.disassociateAddress(
                input: DisassociateAddressInput(
                    associationId: associationId
                )
            )
        } catch {
            print("*** Unable to disassociate the IP address: \(error.localizedDescription)")
        }
    }

import AWSEC2

    /// Release an allocated Elastic IP.
    /// 
    /// - Parameter allocationId: The allocation ID of the Elastic IP to
    ///   release.
    func releaseAddress(allocationId: String?) async {
        do {
            _ = try await ec2Client.releaseAddress(
                input: ReleaseAddressInput(
                    allocationId: allocationId
                )
            )
        } catch {
            print("*** Unable to release the IP address: \(error.localizedDescription)")
        }
    }

import AWSEC2

    /// Create and return a new EC2 instance.
    /// 
    /// - Parameters:
    ///   - imageId: The image ID of the AMI to use when creating the instance.
    ///   - instanceType: The type of instance to create.
    ///   - keyPairName: The RSA key pair's name to use to secure the instance.
    ///   - securityGroups: The security group or groups to add the instance
    ///     to.
    ///
    /// - Returns: The EC2 instance as an `EC2ClientTypes.Instance` object.
    func runInstance(imageId: String, instanceType: EC2ClientTypes.InstanceType,
                        keyPairName: String, securityGroups: [String]?) async -> EC2ClientTypes.Instance? {
        do {
            let output = try await ec2Client.runInstances(
                input: RunInstancesInput(
                    imageId: imageId,
                    instanceType: instanceType,
                    keyName: keyPairName,
                    maxCount: 1,
                    minCount: 1,
                    securityGroupIds: securityGroups
                )
            )

            guard let instances = output.instances else {
                print("*** Unable to create the instance.")
                return nil
            }

            return instances[0]
        } catch {
            print("*** Error creating the instance: \(error.localizedDescription)")
            return nil
        }
    }

import AWSEC2

    /// Start the specified instance.
    /// 
    /// - Parameters:
    ///   - instanceId: The ID of the instance to start.
    ///   - waitUntilStarted: If `true`, execution waits until the instance
    ///     has started. Otherwise, execution continues and the instance starts
    ///     asynchronously.
    ///
    /// - Returns: `true` if the image is successfully started (or is left to
    ///   start asynchronously). `false` if the instance doesn't start.
    func startInstance(instanceId: String, waitUntilStarted: Bool = false) async -> Bool {
        let instanceList = [instanceId]

        do {
            _ = try await ec2Client.startInstances(
                input: StartInstancesInput(
                    instanceIds: instanceList
                )
            )

            if waitUntilStarted {
                print("Waiting for the instance to start...")

                let waitOptions = WaiterOptions(maxWaitTime: 60.0)
                let output = try await ec2Client.waitUntilInstanceRunning(
                    options: waitOptions,
                    input: DescribeInstancesInput(
                        instanceIds: instanceList
                    )
                )
                switch output.result {
                case .success:
                    return true
                case .failure:
                    return false
                }
            } else {
                return true
            }
        } catch {
            print("*** Unable to start the instance: \(error.localizedDescription)")
            return false
        }
    }

import AWSEC2

    /// Stop the specified instance.
    /// 
    /// - Parameters:
    ///   - instanceId: The ID of the instance to stop.
    ///   - waitUntilStopped: If `true`, execution waits until the instance
    ///     has stopped. Otherwise, execution continues and the instance stops
    ///     asynchronously.
    ///
    /// - Returns: `true` if the image is successfully stopped (or is left to
    ///   stop asynchronously). `false` if the instance doesn't stop.
    func stopInstance(instanceId: String, waitUntilStopped: Bool = false) async -> Bool {
        let instanceList = [instanceId]

        do {
            _ = try await ec2Client.stopInstances(
                input: StopInstancesInput(
                    instanceIds: instanceList
                )
            )

            if waitUntilStopped {
                print("Waiting for the instance to stop. Please be patient!")

                let waitOptions = WaiterOptions(maxWaitTime: 600)
                let output = try await ec2Client.waitUntilInstanceStopped(
                    options: waitOptions,
                    input: DescribeInstancesInput(
                        instanceIds: instanceList
                    )
                )

                switch output.result {
                case .success:
                    return true
                case .failure:
                    return false
                }
            } else {
                return true
            }
        } catch {
            print("*** Unable to stop the instance: \(error.localizedDescription)")
            return false
        }
    }

import AWSEC2

    /// Terminate the specified instance.
    ///
    /// - Parameters:
    ///   - instanceId: The instance to terminate.
    ///   - waitUntilTerminated: Whether or not to wait until the instance is
    ///     terminated before returning.
    /// 
    /// - Returns: `true` if terminated successfully. `false` if not or if an
    ///   error occurs.
    func terminateInstance(instanceId: String, waitUntilTerminated: Bool = false) async -> Bool {
        let instanceList = [instanceId]

        do {
            _ = try await ec2Client.terminateInstances(
                input: TerminateInstancesInput(
                    instanceIds: instanceList
                )
            )

            if waitUntilTerminated {
                print("Waiting for the instance to terminate...")

                let waitOptions = WaiterOptions(maxWaitTime: 600.0)
                let output = try await ec2Client.waitUntilInstanceTerminated(
                    options: waitOptions,
                    input: DescribeInstancesInput(
                        instanceIds: instanceList
                    )
                )

                switch output.result {
                case .success:
                    return true
                case .failure:
                    return false
                }
            } else {
                return true
            }
        } catch {
            print("*** Unable to terminate the instance: \(error.localizedDescription)")
            return false
        }
    }