CMake : parent directory?

How to find the parent directory in CMake ?

Assume that ${MYPRO开发者_Go百科JECT_DIR}=/dir1/dir2/dir3/myproject/ and I want ${PARENT_DIR}=/dir1/dir2/dir3/.

How to do that ? SET(PARENT_DIR ${MYPROJECT_DIR}/../) doesn't seem to be the right syntax.

For CMake 3.20 and newer, the recommended way is to use cmake_path with a PARENT_PATH option:

cmake_path(GET MYPROJECT_DIR PARENT_PATH PARENT_DIR)

For older versions up to CMake 2.8.12, use the get_filename_component command with the DIRECTORY option:

get_filename_component(PARENT_DIR ${MYPROJECT_DIR} DIRECTORY)

For versions of CMake older than 2.8.12, use the PATH option:

set (MYPROJECT_DIR /dir1/dir2/dir3/myproject/)
get_filename_component(PARENT_DIR ${MYPROJECT_DIR} PATH)

As of CMake 3.20, you can use the cmake_path command to get the parent directory of a given path:

cmake_path(GET <path-var> PARENT_PATH <out-var>)

This command supersedes the get_filename_component command.

So, in your example, it would look like this:

cmake_path(GET MYPROJECT_DIR PARENT_PATH PARENT_DIR)

You can also check if the path has a parent directory component first:

cmake_path(HAS_PARENT_PATH MYPROJECT_DIR MyDir_HAS_PARENT)
if(MyDir_HAS_PARENT)
    cmake_path(GET MYPROJECT_DIR PARENT_PATH PARENT_DIR)
endif()

This doesn't actually check the filesystem to verify a valid path, but it is a really useful path manipulation command.

For me it didn't work (at cmake 3.18). I ended up using:

get_filename_component(VAR_PARENT ${MYPROJECT_DIR}/.. ABSOLUTE)