CMake: Setting File Permissions During Installation
Problem: You've created a fantastic application using CMake, but you need to ensure specific files within your installation have particular permissions (read-only, executable, etc.) for proper functionality.
Rephrased: Imagine you built a program that needs to access certain files, but these files need special permissions like being executable. How do you tell CMake to apply these permissions during the installation process?
Scenario: Let's say you have a script named my_script.py within your project that needs to be executable by the user after installation. Here's a basic CMakeLists.txt file:
project(MyProject)
# ... other CMake commands ...
# Install the script
install(FILES my_script.py DESTINATION bin)
This code snippet installs the script to the "bin" directory during installation, but it doesn't change the file's permissions.
Solution: CMake provides the file(PERMISSIONS) command to set file permissions during the install process. Here's how to modify the previous example to make my_script.py executable:
project(MyProject)
# ... other CMake commands ...
# Install the script
install(FILES my_script.py DESTINATION bin)
# Make the script executable
file(PERMISSIONS my_script.py OWNER_EXECUTE GROUP_EXECUTE WORLD_EXECUTE)
Explanation:
file(PERMISSIONS <file> OWNER_EXECUTE GROUP_EXECUTE WORLD_EXECUTE): This command modifies the permissions of the specified file (my_script.py).OWNER_EXECUTE: Grants the file owner permission to execute the script.GROUP_EXECUTE: Grants the file group permission to execute the script.WORLD_EXECUTE: Grants everyone permission to execute the script.
Key Points:
- Flexibility: You can use combinations of permissions. For example,
OWNER_WRITE GROUP_READ WORLD_READwould give the owner write access, the group read access, and everyone else read access. - Target Specificity: You can use the
install(TARGETS)command for target-specific installation, including setting file permissions for generated executables or libraries. - Platform Considerations: The specific permission flags might differ slightly across platforms (Windows, macOS, Linux). Refer to CMake documentation for platform-specific details.
Beyond the Basics:
- Advanced Permissions: For more complex permission scenarios, consider using the
chmodcommand within your CMake build process, or external scripting languages like Python or Bash. - Security Considerations: Carefully consider the security implications of changing file permissions. Avoid granting unnecessary permissions to ensure system security.
- Documentation: Document your CMake code, especially permission settings, to maintain clarity for your project and future contributors.
Additional Resources:
By understanding and applying CMake's file permission commands, you can ensure your applications function correctly with the necessary access rights, making your software development process more secure and efficient.
