Understanding CMake's DEPLOYMENT_REMOTE_DIRECTORY Property

CMake and Deployment

• It can also be used to manage deployment tasks, which involve copying the generated artifacts (executables, libraries, data files) to a designated location.
• CMake is a cross-platform build system that generates platform-specific instructions to compile and link your source code into an executable or library.

DEPLOYMENT_REMOTE_DIRECTORY Property

• It allows you to specify the remote directory (on a different machine or filesystem) where the generated artifacts for a particular target should be copied during the build process.
• This property is part of CMake's target properties and is specifically designed for deployment purposes.

How It Works

1. • In your CMakeLists.txt file, you can define a target (e.g., an executable) and set the DEPLOYMENT_REMOTE_DIRECTORY property for that target.
   • The property value should be the path to the remote directory on the target machine where you want the artifacts to be deployed. You can use macros or environment variables to make the path dynamic if needed.

2. Build Process
   

   • When you run cmake --build . or your IDE's build command, CMake not only generates the build files (makefiles, Visual Studio project files, etc.) for compiling and linking your code, but it also considers deployment targets.

3. Deployment Step (Optional)
   

   • CMake itself doesn't perform the actual deployment (copying files). However, some build systems or custom commands integrated into the build process can leverage this property.
   • You might have a custom target that uses the DEPLOYMENT_REMOTE_DIRECTORY property to construct a command that executes a tool like scp or rsync to transfer the artifacts to the remote machine.

Example

add_executable(my_program main.cpp)
set_property(TARGET my_program PROPERTY DEPLOYMENT_REMOTE_DIRECTORY "/remote/path/on/target/machine")

# Optional custom target for deployment (pseudocode)
add_custom_target(deploy_my_program
  COMMAND scp ${PROJECT_SOURCE_DIR}/my_program ${DEPLOYMENT_REMOTE_DIRECTORY}/${PROJECT_NAME}
  DEPENDS my_program
)

In this example:

• The optional deploy_my_program target (not a standard CMake target) demonstrates how you might use the property to construct a deployment command (assuming scp is available).
• The DEPLOYMENT_REMOTE_DIRECTORY property is set to /remote/path/on/target/machine.
• The my_program executable is built.

Key Points

• You'll likely need additional tools or custom commands to perform the actual file transfer.
• It specifies the remote destination for deployment, not the deployment mechanism itself.
• DEPLOYMENT_REMOTE_DIRECTORY is a CMake property, not a built-in command.

---

Simple Deployment Using Custom Target (Linux/macOS)

add_executable(my_program main.cpp)
set_property(TARGET my_program PROPERTY DEPLOYMENT_REMOTE_DIRECTORY "/home/user/projects/deploy_dir")

add_custom_target(deploy_my_program
  COMMAND scp ${PROJECT_SOURCE_DIR}/my_program ${DEPLOYMENT_REMOTE_DIRECTORY}
  DEPENDS my_program
)

This example assumes you have SSH access to the target machine and the scp tool is available. The deploy_my_program target uses scp to copy the my_program executable to the remote directory after it's built.

Deployment with Build Configuration (Windows)

if(WIN32)
  set(DEPLOY_COMMAND "copy")
else()
  set(DEPLOY_COMMAND "cp")
endif()

add_executable(my_program main.cpp)
set_property(TARGET my_program PROPERTY DEPLOYMENT_REMOTE_DIRECTORY "\\remote\share\path")

add_custom_target(deploy_my_program
  COMMAND ${DEPLOY_COMMAND} ${PROJECT_SOURCE_DIR}/my_program ${DEPLOYMENT_REMOTE_DIRECTORY}
  DEPENDS my_program
)

This example uses a CMake conditional statement to determine the appropriate command for copying files based on the operating system (either copy on Windows or cp on Linux/macOS). The DEPLOYMENT_REMOTE_DIRECTORY is set to a Windows share path.

Deployment Using External Tool (e.g., Rsync)

find_program(RSYNC rsync)  # Assuming rsync is installed and in PATH

add_executable(my_program main.cpp)
set_property(TARGET my_program PROPERTY DEPLOYMENT_REMOTE_DIRECTORY "user@host:/remote/path")

add_custom_target(deploy_my_program
  COMMAND ${RSYNC} -avz ${PROJECT_SOURCE_DIR}/my_program ${DEPLOYMENT_REMOTE_DIRECTORY}
  DEPENDS my_program
)

This example uses the find_program command to check if the rsync tool is available. If found, the deploy_my_program target uses rsync with the -avz flags (archive, verbose, and compress) to transfer the my_program executable along with additional files or directories (if needed) to the remote machine specified by the DEPLOYMENT_REMOTE_DIRECTORY property.

---

CPack

• This approach provides a more standardized packaging solution that can be easily distributed and installed on target machines.
• You can configure CPack to include specific target artifacts and define installation paths within the package itself.
• CMake offers CPack, a component that helps create installation packages for various platforms (e.g., .deb, .rpm, MSI installers).

Custom Commands

• This method offers flexibility but requires managing the deployment logic within your build scripts.
• This could involve using tools like scp, rsync, or platform-specific utilities to transfer files to the remote location.
• You can directly use custom commands within your CMakeLists.txt file to perform deployment tasks.

• This approach allows separation of concerns between configuring the build and the deployment itself.
• You can leverage these features to integrate your deployment process into the build workflow.
• If you're using an IDE or a build system like Make, they might offer mechanisms for post-build steps or custom targets.

Approach	Advantages	Disadvantages
DEPLOYMENT_REMOTE_DIRECTORY	Simple for basic deployment, specifies target location	Requires additional custom commands for transfer
CPack	Standardized packaging, platform-independent deployment	More complex setup, requires package generation
Custom Commands	Flexible, integrates with existing tools	Requires managing deployment logic in CMakeLists.txt
Build System Integration	Separates build and deployment concerns	Requires knowledge of specific build system features