Getting started with the Amazon SDK for C++ code examples - Amazon SDK for C++
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Getting started with the Amazon SDK for C++ code examples

Structure of the code examples

The C++ example folder on Github contains project folders for each Amazon service. Typically, individual .cpp source files in the folders demonstrate a specific functionality or action for that service. For example, for Amazon DynamoDB, getting an item from the database and uploading an item to the database are two different types of action, so there is a separate file for each in the DynamoDB folder: get_item.cpp and put_item.cpp. Each .cpp file contains a main() function as an entrypoint to a standalone executable. The project executables are generated in a folder designated by your build system, and there is one executable file corresponding to each example source file. The file name of the executable follows the conventions of the platform such as {name}.exe or just {name} and any custom prefix CMakeLists.txt applies such as run_.

To run an example functionality
  1. Download the desired code example from the Amazon Code Examples Repository on GitHub.

  2. Open a .cpp file to explore its main() function and any called methods.

  3. Build the project, as demonstrated with the starter example in Getting started using the Amazon SDK for C++. Note that building the project generates each executable for every source file in the project.

  4. Run the executable for the selected functionality.

    • In a command prompt, run that program using the executable based on the name of the *.cpp file.

    • If you are working within an IDE, choose the .cpp file of the functionality you want to demonstrate and select it as the startup option (or startup object).

Unit tests

Some examples include unit tests. The unit tests are in the tests folder, and there is one test source file for each example source file. Each test source file builds to its own executable that you can run by using the command line.

CMakeLists.txt file

The folder for each service contains a file named CMakeLists.txt file. Many of these files contain a construct similar to the following:

foreach(EXAMPLE IN LISTS EXAMPLES) add_executable(${EXAMPLE} ${EXAMPLE}.cpp) target_link_libraries(${EXAMPLE} aws-cpp-sdk-email aws-cpp-sdk-core) endforeach()

For each .cpp file in the folder, the CMakeLists.txt file builds an executable (cmake: add_executable) with a name based on the name of the source code file without the file extension.

Using Amazon for troubleshooting and diagnostics

As you learn to develop applications with the Amazon SDK for C++, it's also valuable to get comfortable in using both the Amazon Web Services Management Console and the Amazon CLI. These tools can be used interchangeably for various troubleshooting and diagnostics .

The following tutorial shows you an example of these troubleshooting and diagnostics tasks. It focuses on the Access denied error, which can be encountered for several different reasons. The tutorial shows an example of how you might determine the actual cause of the error. It focuses on two of the possible causes: incorrect permissions for the current user and a resource that isn't available to the current user.

To get the project source and executables
  1. Download the Amazon S3 code example folder from Amazon Code Examples Repository on GitHub.

  2. Open delete_bucket.cpp and notice that there are two methods: main() and DeleteBucket(). DeleteBucket() uses the SDK to delete the bucket.

  3. Also notice that there are two "TODO" blocks with instructions for updating the code. Do NOT perform these updates yet; they will be performed later in the tutorial.

  4. Build the Amazon S3 example, using the same build steps explained in Getting started using the Amazon SDK for C++. The build process generates an executable for each source file.

  5. Open a command prompt to the folder where your build system generated your build executables. Run the executable run_create_bucket (your actual executable filename will differ based on your operating system). This creates a bucket in your account (so that you have one to delete).

  6. In the command prompt, run the executable run_delete_bucket.

  7. Confirm that you get an Access Denied error message. Getting an Access Denied error message leads you to question whether you created a user with full permissions for Amazon S3, which you'll verify next.

To install the Amazon CLI and find the username that is making calls to Amazon
  1. To install the latest Amazon CLI to your development machine, see Installing the Amazon CLI in the Amazon Command Line Interface User Guide.

  2. To verify the Amazon CLI is working, open a command prompt and run command aws -\-version

    $ aws -\-version aws-cli/2.1.29 Python/3.8.8 Windows/10 exe/AMD64 prompt/off
  3. To obtain the username that is actually making the calls to Amazon, run the Amazon CLI command aws sts get-caller-identity. In the following example output, that username is userX

    $ aws sts get-caller-identity { "UserId": "A12BCD34E5FGHI6JKLM", "Account": "1234567890987", "Arn": "arn:aws:iam::1234567890987:user/userX" }

    There are many ways to specify credentials, but if you followed the approach in Providing Amazon credentials then this username comes from your Amazon shared credentials file. During that procedure you granted your user AmazonS3FullAccess permissions.

    Note

    Generally, most Amazon CLI commands follow the syntax structure of:

    $ aws <command> <subcommand> [options and parameters]

    where command is the service, and subcommand is the method being called on that service. For more details, see Command structure in the Amazon CLI in the Amazon Command Line Interface User Guide.

To verify whether a user has permission to delete a bucket
  1. Open the Amazon Web Services Management Console and log in. For more details, see Getting Started with the Amazon Web Services Management Console.

  2. In the main navigation bar, for Search for services..., enter IAM and select the IAM service from the results.

  3. From the Dashboard sidebar, or under IAM Resources, select Users.

  4. From the table of users available for your account, select the username obtained in the preceding procedure.

  5. Choose the Permissions tab of the Summary page, under the Policy name table, select AmazonS3FullAccess.

  6. Look at the Policy summary and the JSON data. Verify that this user has full rights for the Amazon S3 service.

    "Effect": "Allow", "Action": "s3:*", "Resource": "*"

This process of elimination is common in ruling out where the problem might be. In this case, you've verified that the user does have the correct permissions, so the problem must be something else. That is, since you have the correct permissions to access your buckets, the Access Denied error may mean that you are trying to access a bucket that isn't yours. Next, review the bucket name in the code, which is "my-bucket". Notice that a bucket with that name doesn't exist in your account, and thus, you cannot 'access' it.

To update the code example so it runs successfully
  1. Back in delete_bucket.cpp's main() function, change the Region, using the enum, to the Region of your account. To find your Region of your account, log into the Amazon Web Services Management Console, and locate the Region in the upper right-hand corner. Also in main(), change the bucket name to a bucket that does exist in your account. There are several ways to find your current bucket names:

    • You can use the run_list_buckets executable that also exists in this code example's folder to programatically get the names of your buckets.

    • Alternatively, you can also use the following Amazon CLI command to list your Amazon S3 buckets.

      $ aws s3 ls 2022-01-05 14:27:48 my-bucket-28621ccd-4a48-45be-b660-5252f75635a4
    • Alternatively, you can also use the Amazon Web Services Management Console. In the main navigation bar, in Search for services..., enter S3. The Buckets page lists your account's buckets.

  2. Rebuild the code and run the updated executable run_delete_bucket.

  3. Using either the Amazon Web Services Management Console or the Amazon CLI, verify that the Amazon S3 bucket that you created earlier has been deleted.

Building and Debugging Code Examples in Visual Studio

Note

NuGet SDK packages are deprecated. Even if you use Visual Studio, it is recommended to still get the latest source code from GitHub, and build the Amazon SDK for C++ from source following the instructions.

Building and running the Amazon S3 code example
  1. Obtain the Amazon S3 example source code. This procedure uses the Amazon S3 code examples using the Amazon SDK for C++ code example to get up and running using Visual Studio.

  2. In Windows Explorer, navigate to the s3 folder (e.g. \aws-doc-sdk-examples\cpp\example_code\s3).

  3. Right click on the s3 example folder and choose Open with Visual Studio.  Visual Studio for CMake projects don’t have a 'project' file, rather, it is the whole folder.

  4. In the Configuration Selector dropdown in the top menu of Visual Studio, ensure that the selected configuration matches the build type that you selected when building the SDK from source.  E.g. a Debug configuration should be selected if you built from source using debug (-DCMAKE_BUILD_TYPE=Debug in the CMake command line from the SDK installation instructions).

  5. If you are on Windows, delete the file list_buckets_disabling_dns_cache.cpp before building the project because it relies on the curl HttpClient of Linux.   This source file is not for Windows users (unless you have taken additional steps to explicitly add cURL support).

  6. Open file CMakeLists.txt.

  7. Click Save. Every time you click Save on the CMakeLists.txt file, Visual Studio refreshes the CMake-generated files.  If you have your Output tab displayed, you can see the resulting log messages from this generation.

    • There is a drop-down box within the Output tab that says: "Show output from:" and CMake should be the option selected by default.

    • Last message output should say "CMake generation finished."  

    • If last message is not this, then the CMake file has issues. Do not proceed to further steps until this is resolved.  See Troubleshooting build issues.

    • Note that the CMake cache is used by CMake for speed. If you are working through CMake issues, you want to ensure a ‘clean slate’ so that the error messages you are given is actually reflective of your most recent changes.  In the Solution Explorer, right-click on CMakeLists.txt and choose CMake Cache, then choose Delete Cache. Do this frequently when working progressively through CMake issues.

  8. To build and run examples from within Visual Studio, Visual Studio places executables in a different folder structure than the command line. To run the code, the SDK executables must be copied to the right place.  Find the “TODO” line of the CMakeLists file (~line 40) and choose the one commented for use in Visual Studio. Visual Studio does not use a subfolder dedicated to the build type so this is not included.  Switch the commented-out line in the CMakeLists.txt file for Visual Studio use.

  9. Delete the CMake cache (as described above), click in the CMakeLists.txt file to select/activate the tab, and choose Save on the CMakeLists.txt file again to initiate the CMake build files generation.

  10. Open the source file of the ‘program’ you wish to run.

    • For example, open list_buckets.cpp.

    • The Amazon S3 example folder is coded so that each showcased ‘feature’ of Amazon S3 is demonstrated in a dedicated executable for just that feature.  E.g. list_buckets.cpp will become an executable that only demonstrates the listing of buckets.

  11. In the top menu, choose Build, then choose Build All.

    • The Output tab’s Show output from should reflect the selection of Build, and show all the building and linking messages.

    • The last output should be: "Build All succeeded."

    • Now executables for each of the individual source files are generated.  You can confirm this by looking in the build output directory (e.g. \aws-doc-sdk-examples\cpp\example_code\s3\out\build\x64-Debug).

    • Note that the executables are prefixed with “run_” because the CMakeLists.txt file dictates this.

  12. In the top menu, there is a green arrow and a drop-down selector for Debug Target.  Choose run_list_buckets.exe.

  13. Click the green arrow run button to Select Startup Item.

  14. A Visual Studio Debug Console window will open and display the output of the code.

  15. Press a key to close the window, or manually close the window, to terminate the program.  You can also set breakpoints in the code and when you click run again the breakpoints will be hit.