How to use the command `cmake` (with examples)

CMake is a cross-platform build automation system that generates recipes for native build systems. It provides a simple and efficient way to manage the build process of software projects. In this article, we will explore various use cases of the cmake command.

Use case 1: Generate a build recipe in the current directory

Code:

cmake path/to/project_directory

Motivation:

Generating a build recipe is the first step in building a project with CMake. By specifying the path to the project directory, CMake will look for a CMakeLists.txt file and generate the necessary build files in the current directory.

Explanation:

• cmake: invokes the CMake command-line tool.
• path/to/project_directory: the path to the directory where the project’s CMakeLists.txt file is located.

Example output:

CMake generates the build files in the current directory, which can then be used to build the project.

Use case 2: Generate a build recipe with a specific build type

Code:

cmake path/to/project_directory -D CMAKE_BUILD_TYPE=Release

Motivation:

Different build types, such as Release and Debug, have different optimization and debugging options. By specifying the CMAKE_BUILD_TYPE variable with the -D flag, we can generate a build recipe with a specific build type, such as Release.

Explanation:

• cmake: invokes the CMake command-line tool.
• path/to/project_directory: the path to the directory where the project’s CMakeLists.txt file is located.
• -D CMAKE_BUILD_TYPE=Release: sets the CMAKE_BUILD_TYPE variable to Release, specifying the build type.

Example output:

CMake generates the build files in the current directory, with the build type set to Release.

Use case 3: Generate a build recipe using a specific generator

Code:

cmake -G generator_name path/to/project_directory

Motivation:

CMake supports various build systems, such as Makefiles, Ninja, and IDE-specific project files. By specifying a generator with the -G flag, we can generate a build recipe using the desired underlying build system.

Explanation:

• cmake: invokes the CMake command-line tool.
• -G generator_name: sets the generator to use the specified build system.
• path/to/project_directory: the path to the directory where the project’s CMakeLists.txt file is located.

Example output:

CMake generates the build files in the current directory, using the specified generator as the underlying build system.

Use case 4: Build artifacts using a generated recipe

Code:

cmake --build path/to/build_directory

Motivation:

Once the build files are generated, we can use the cmake --build command to build the project using the generated recipe. By specifying the path to the build directory, CMake will locate the necessary build files and initiate the build process.

Explanation:

• cmake: invokes the CMake command-line tool.
• --build path/to/build_directory: specifies the path to the build directory where the generated build files are located.

Example output:

CMake builds the project using the generated recipe in the specified build directory.

Use case 5: Install build artifacts and strip debugging symbols

Code:

cmake --install path/to/build_directory --strip

Motivation:

Installing the build artifacts into a specific location is often required to make the project globally available. By using the --install flag, CMake will install the built artifacts into the specified location and strip the debugging symbols, reducing the file size.

Explanation:

• cmake: invokes the CMake command-line tool.
• --install path/to/build_directory: specifies the path to the build directory where the generated build files are located.
• --strip: instructs CMake to strip debugging symbols from the installed artifacts.

Example output:

CMake installs the built artifacts into the specified installation directory, while stripping the debugging symbols.

Use case 6: Install build artifacts with a custom prefix

Code:

cmake --install path/to/build_directory --strip --prefix path/to/directory

Motivation:

The installation path for build artifacts can be customized by specifying a custom prefix. This allows us to control where the project’s artifacts are installed on the system.

Explanation:

• cmake: invokes the CMake command-line tool.
• --install path/to/build_directory: specifies the path to the build directory where the generated build files are located.
• --strip: instructs CMake to strip debugging symbols from the installed artifacts.
• --prefix path/to/directory: sets the custom prefix for the installation path.

Example output:

CMake installs the built artifacts into the specified installation directory, using the custom prefix for paths.

Use case 7: Build a custom target

Code:

cmake --build path/to/build_directory --target target_name

Motivation:

In some cases, it may be necessary to build only a specific target within a project. By specifying the --target flag followed by the target name, we can build only that specific target.

Explanation:

• cmake: invokes the CMake command-line tool.
• --build path/to/build_directory: specifies the path to the build directory where the generated build files are located.
• --target target_name: builds only the specified target.

Example output:

CMake builds the project, specifically targeting the specified custom target.

Use case 8: Display help and obtain a list of generators

Code:

cmake --help

Motivation:

Obtaining help and a list of available generators can be helpful, especially when working with CMake for the first time or when exploring different build system options.

Explanation:

• cmake: invokes the CMake command-line tool.
• --help: displays the help information and available options.

Example output:

CMake displays the help information, including a list of command-line options and available generators.

Conclusion:

In this article, we explored various use cases of the cmake command. From generating build recipes to building artifacts and installing them, CMake provides a powerful and flexible tool for managing the build process of software projects. Understanding the different use cases of the cmake command allows developers to efficiently build and distribute their projects.