private async downloadAndInstall(downloadUrls: string[]) {
        let downloaded = false;
        let downloadPath = "";
        for (const url of downloadUrls) {
            try {
                downloadPath = await toolLib.downloadTool(url);
                downloaded = true;
                break;
            } catch (error) {
                tl.warning(tl.loc("CouldNotDownload", url, JSON.stringify(error)));
            }
        }

        if (!downloaded) {
            throw tl.loc("FailedToDownloadPackage");
        }

        // extract
        console.log(tl.loc("ExtractingPackage", downloadPath));
        let extPath: string = tl.osType().match(/^Win/) ? await toolLib.extractZip(downloadPath) : await toolLib.extractTar(downloadPath);

        // cache tool
        console.log(tl.loc("CachingTool"));
        let cachedDir = await toolLib.cacheDir(extPath, this.cachedToolName, this.version);
        console.log(tl.loc("SuccessfullyInstalled", this.packageType, this.version));
        return cachedDir;
    }

function getDefaultProps() {
    return {
        releaseuri: tl.getVariable('Release.ReleaseUri'),
        releaseid: tl.getVariable('Release.ReleaseId'),
        builduri: tl.getVariable('Build.BuildUri'),
        buildid: tl.getVariable('Build.Buildid'),
        osType: tl.osType()
    };
}

function shouldUseVstsNuGetPush(isInternalFeed: boolean, conflictsAllowed: boolean, nugetExePath: string): boolean {
    if (tl.osType() !== "Windows_NT"){
        tl.debug("Running on a non-windows platform so NuGet.exe will be used.");
        if(conflictsAllowed){
            tl.warning(tl.loc("Warning_SkipConflictsNotSupportedUnixAgents"));
        }
        return false;
    }

    if (!isInternalFeed)
    {
        tl.debug("Pushing to an external feed so NuGet.exe will be used.");
        return false;
    }

    if (commandHelper.isOnPremisesTfs())
    {
        tl.debug("Pushing to an onPrem environment, only NuGet.exe is supported.");
        if(conflictsAllowed){
            tl.warning(tl.loc("Warning_AllowDuplicatesOnlyAvailableHosted"));
        }
        return false;
    }

    const nugetOverrideFlag = tl.getVariable("NuGet.ForceNuGetForPush");
    if (nugetOverrideFlag === "true") {
        tl.debug("NuGet.exe is force enabled for publish.");
        if(conflictsAllowed)
        {
            tl.warning(tl.loc("Warning_ForceNuGetCannotSkipConflicts"));
        }
        return false;
    }

    if (nugetOverrideFlag === "false") {
        tl.debug("NuGet.exe is force disabled for publish.");
        return true;
    }

    const vstsNuGetPushOverrideFlag = tl.getVariable("NuGet.ForceVstsNuGetPushForPush");
    if (vstsNuGetPushOverrideFlag === "true") {
        tl.debug("VstsNuGetPush.exe is force enabled for publish.");
        return true;
    }

    if (vstsNuGetPushOverrideFlag === "false") {
        tl.debug("VstsNuGetPush.exe is force disabled for publish.");
        if(conflictsAllowed)
        {
            tl.warning(tl.loc("Warning_ForceNuGetCannotSkipConflicts"));
        }
        return false;
    }

    return true;
}

export function getOctoCommandRunner(command: string) : Option<ToolRunner> {
    const isWindows = /windows/i.test(tasks.osType());
    if(isWindows){
        return stringOption(tasks.which(`${ToolName}`, false))
        .map(tasks.tool)
        .map(x => x.arg(command));
    }

    return getPortableOctoCommandRunner(command);
}

    public async downloadAndInstall(versionInfo: VersionInfo, downloadUrl: string): Promise<void> {
        if (!versionInfo || !versionInfo.getVersion() || !downloadUrl || !url.parse(downloadUrl)) {
            throw tl.loc("VersionCanNotBeDownloadedFromUrl", versionInfo, downloadUrl);
        }

        let version = versionInfo.getVersion();

        try {
            try {
                var downloadPath = await toolLib.downloadTool(downloadUrl)
            }
            catch (ex) {
                throw tl.loc("CouldNotDownload", downloadUrl, ex);
            }

            // Extract
            console.log(tl.loc("ExtractingPackage", downloadPath));
            try {
                var extPath = tl.osType().match(/^Win/) ? await toolLib.extractZip(downloadPath) : await toolLib.extractTar(downloadPath);
            }
            catch (ex) {
                throw tl.loc("FailedWhileExtractingPacakge", ex);
            }

            // Copy folders
            tl.debug(tl.loc("CopyingFoldersIntoPath", this.installationPath));
            var allRootLevelEnteriesInDir: string[] = tl.ls("", [extPath]).map(name => path.join(extPath, name));
            var directoriesTobeCopied: string[] = allRootLevelEnteriesInDir.filter(path => fs.lstatSync(path).isDirectory());
            directoriesTobeCopied.forEach((directoryPath) => {
                tl.cp(directoryPath, this.installationPath, "-rf", false);
            });

            // Copy files
            try {
                if (this.packageType == utils.Constants.sdk && this.isLatestInstalledVersion(version)) {
                    tl.debug(tl.loc("CopyingFilesIntoPath", this.installationPath));
                    var filesToBeCopied = allRootLevelEnteriesInDir.filter(path => !fs.lstatSync(path).isDirectory());
                    filesToBeCopied.forEach((filePath) => {
                        tl.cp(filePath, this.installationPath, "-f", false);
                    });
                }
            }
            catch (ex) {
                tl.warning(tl.loc("FailedToCopyTopLevelFiles", this.installationPath, ex));
            }

            // Cache tool
            this.createInstallationCompleteFile(versionInfo);

            console.log(tl.loc("SuccessfullyInstalled", this.packageType, version));
        }
        catch (ex) {
            throw tl.loc("FailedWhileInstallingVersionAtPath", version, this.installationPath, ex);
        }
    }

    private detectMachineOS(): string[] {
        let osSuffix = [];
        let scriptRunner: trm.ToolRunner;

        try {
            console.log(tl.loc("DetectingPlatform"));
            if (tl.osType().match(/^Win/)) {
                let escapedScript = path.join(this.getCurrentDir(), 'externals', 'get-os-platform.ps1').replace(/'/g, "''");
                let command = `& '${escapedScript}'`

                let powershellPath = tl.which('powershell', true);
                scriptRunner = tl.tool(powershellPath)
                    .line('-NoLogo -Sta -NoProfile -NonInteractive -ExecutionPolicy Unrestricted -Command')
                    .arg(command);
            }
            else {
                let scriptPath = path.join(this.getCurrentDir(), 'externals', 'get-os-distro.sh');
                this.setFileAttribute(scriptPath, "777");

                scriptRunner = tl.tool(tl.which(scriptPath, true));
            }

            let result: trm.IExecSyncResult = scriptRunner.execSync();

            if (result.code != 0) {
                throw tl.loc("getMachinePlatformFailed", result.error ? result.error.message : result.stderr);
            }

            let output: string = result.stdout;

            let index;
            if ((index = output.indexOf("Primary:")) >= 0) {
                let primary = output.substr(index + "Primary:".length).split(os.EOL)[0];
                osSuffix.push(primary);
                console.log(tl.loc("PrimaryPlatform", primary));
            }

            if ((index = output.indexOf("Legacy:")) >= 0) {
                let legacy = output.substr(index + "Legacy:".length).split(os.EOL)[0];
                osSuffix.push(legacy);
                console.log(tl.loc("LegacyPlatform", legacy));
            }

            if (osSuffix.length == 0) {
                throw tl.loc("CouldNotDetectPlatform");
            }
        }
        catch (ex) {
            throw tl.loc("FailedInDetectingMachineArch", JSON.stringify(ex));
        }

        return osSuffix;
    }

function addDotNetCoreToolPath() {
    try {
        let globalToolPath: string = "";
        if (tl.osType().match(/^Win/)) {
            globalToolPath = path.join(process.env.USERPROFILE, Constants.relativeGlobalToolPath);
        } else {
            globalToolPath = path.join(process.env.HOME, Constants.relativeGlobalToolPath);
        }

        console.log(tl.loc("PrependGlobalToolPath"));
        tl.mkdirP(globalToolPath);
        toolLib.prependPath(globalToolPath);
    } catch (error) {
        //nop
        console.log(tl.loc("ErrorWhileSettingDotNetToolPath", JSON.stringify(error)));
    }
}

    private detectMachineOS(): string[] {
        let osSuffix = [];

        if (tl.osType().match(/^Win/)) {
            let primary = "win-" + os.arch();
            osSuffix.push(primary);
            console.log(tl.loc("PrimaryPlatform", primary));
        }
        else {
            let scriptPath = path.join(utilities.getCurrentDir(), 'externals', 'get-os-distro.sh');
            utilities.setFileAttribute(scriptPath, "777");

            let scriptRunner: trm.ToolRunner = tl.tool(tl.which(scriptPath, true));
            let result: trm.IExecSyncResult = scriptRunner.execSync();

            if (result.code != 0) {
                throw tl.loc("getMachinePlatformFailed", result.error ? result.error.message : result.stderr);
            }

            let output: string = result.stdout;

            let index;
            if ((index = output.indexOf("Primary:")) >= 0) {
                let primary = output.substr(index + "Primary:".length).split(os.EOL)[0];
                osSuffix.push(primary);
                console.log(tl.loc("PrimaryPlatform", primary));
            }

            if ((index = output.indexOf("Legacy:")) >= 0) {
                let legacy = output.substr(index + "Legacy:".length).split(os.EOL)[0];
                osSuffix.push(legacy);
                console.log(tl.loc("LegacyPlatform", legacy));
            }

            if (osSuffix.length == 0) {
                throw tl.loc("CouldNotDetectPlatform");
            }
        }

        return osSuffix;
    }

async function acquireDotNetCore(packageType: string, version: string): Promise<string> {
    let downloadUrls = getDownloadUrls(packageType, version);
    let downloadPath: string;

    try {
        // try primary url
        if (!!downloadUrls[0]) {
            console.log(taskLib.loc("DownloadingPrimaryUrl", downloadUrls[0]));
            downloadPath = await toolLib.downloadTool(downloadUrls[0]);
        }
    } catch (error1) {
        console.log(taskLib.loc("PrimaryUrlDownloadFailed", error1));
        try {
            // try secondary url
            if (!!downloadUrls[1]) {
                console.log(taskLib.loc("DownloadingSecondaryUrl", downloadUrls[1]));
                downloadPath = await toolLib.downloadTool(downloadUrls[1]);
            }
        } catch (error2) {
            console.log(taskLib.loc("LegacyUrlDownloadFailed", error2));
            throw taskLib.loc("DownloadFailed", packageType, version);
        }
    }

    // extract
    let extPath: string;
    console.log(taskLib.loc("ExtractingPackage", downloadPath));
    if (taskLib.osType().match(/^Win/)) {
        extPath = await toolLib.extractZip(downloadPath);
    }
    else {
        extPath = await toolLib.extractTar(downloadPath);
    }

    // cache tool
    let cachedToolName = getCachedToolName(packageType);
    console.log(taskLib.loc("CachingTool"));
    let cachedDir =  await toolLib.cacheDir(extPath, cachedToolName, version);
    console.log(taskLib.loc("SuccessfullyInstalled", packageType, version));
    return cachedDir;
}

    public async install() {
        // Check cache
        let toolPath: string;
        let osSuffixes = this.detectMachineOS();
        let parts = osSuffixes[0].split("-");
        this.arch = parts.length > 1 ? parts[1] : "x64";
        toolPath = this.getLocalTool();

        if (!toolPath) {
            // download, extract, cache
            console.log(tl.loc("InstallingAfresh"));
            console.log(tl.loc("GettingDownloadUrl", this.packageType, this.version));
            let downloadUrls = await DotNetCoreReleaseFetcher.getDownloadUrls(osSuffixes, this.version, this.packageType);
            toolPath = await this.downloadAndInstall(downloadUrls);
        } else {
            console.log(tl.loc("UsingCachedTool", toolPath));
        }

        // Prepend the tools path. instructs the agent to prepend for future tasks
        toolLib.prependPath(toolPath);

        try {
            let globalToolPath: string = "";
            if (tl.osType().match(/^Win/)) {
                globalToolPath = path.join(process.env.USERPROFILE, ".dotnet\\tools");
            } else {
                globalToolPath = path.join(process.env.HOME, ".dotnet/tools");
            }

            console.log(tl.loc("PrependGlobalToolPath"));
            tl.mkdirP(globalToolPath);
            toolLib.prependPath(globalToolPath);
        } catch (error) {
            //nop
        }

        // Set DOTNET_ROOT for dotnet core Apphost to find runtime since it is installed to a non well-known location.
        tl.setVariable('DOTNET_ROOT', toolPath);
    }