How to use CMAKE_INSTALL_PREFIX

Question

I want to generate Makefile with install target, making installation to /usr instead of default /usr/local. Assuming that build directory is done in the source subdirectory, I execute:

cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr ..

CMakeCache.txt contains: CMAKE_INSTALL_PREFIX:PATH=/usr (OK?)

Now I execute:

make
make install

All files are still installed to usr/local. What is wrong?

Edit: There is no CMAKE_INSTALL_PREFIX in any of CMakeLists.txt project files. Before running cmake, I delete everything from the output directory. install directives in CMakeLists.txt look like:

install(TARGETS mylibrary DESTINATION lib)

Answer 1

There are two ways to use this variable:

• passing it as a command line argument just like Job mentioned:

  cmake -DCMAKE_INSTALL_PREFIX=< install_path > ..

• assigning value to it in CMakeLists.txt:

  SET(CMAKE_INSTALL_PREFIX < install_path >)

  But do remember to place it BEFORE PROJECT(< project_name>) command, otherwise it will not work!

Answer 2

But do remember to place it BEFORE PROJECT(< project_name>) command, otherwise it will not work!

My first week of using cmake - after some years of GNU autotools - so I am still learning (better then writing m4 macros), but I think modifying CMAKE_INSTALL_PREFIX after setting project is the better place.

CMakeLists.txt

cmake_minimum_required (VERSION 2.8)

set (CMAKE_INSTALL_PREFIX /foo/bar/bubba)
message("CIP = ${CMAKE_INSTALL_PREFIX} (should be /foo/bar/bubba")
project (BarkBark)
message("CIP = ${CMAKE_INSTALL_PREFIX} (should be /foo/bar/bubba")
set (CMAKE_INSTALL_PREFIX /foo/bar/bubba)
message("CIP = ${CMAKE_INSTALL_PREFIX} (should be /foo/bar/bubba")

First run (no cache)

CIP = /foo/bar/bubba (should be /foo/bar/bubba
-- The C compiler identification is GNU 4.4.7
-- etc, etc,...
CIP = /usr/local (should be /foo/bar/bubba
CIP = /foo/bar/bubba (should be /foo/bar/bubba
-- Configuring done
-- Generating done

Second run

CIP = /foo/bar/bubba (should be /foo/bar/bubba
CIP = /foo/bar/bubba (should be /foo/bar/bubba
CIP = /foo/bar/bubba (should be /foo/bar/bubba
-- Configuring done
-- Generating done

Let me know if I am mistaken, I have a lot of learning to do. It's fun.

Answer 3

That should be (see the docs):

cmake -DCMAKE_INSTALL_PREFIX=/usr ..