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)

score 131 · Accepted Answer · edited Oct 10 '12 at 16:30

131

That should be (see the docs):

cmake -DCMAKE_INSTALL_PREFIX=/usr ..

edited Oct 10 '12 at 16:30

James

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answered Jun 05 '11 at 09:24

mtvec

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score 34 · Answer 2 · edited Jan 20 '14 at 15:39

34

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!

edited Jan 20 '14 at 15:39

plaes

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answered Jan 07 '14 at 01:59

ryan_tu

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Strange, the SET() statement works for me only if I place it AFTER the PROJECT() statement (CMake 2.8). – AstroFloyd May 04 '15 at 19:00
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[This answer](http://stackoverflow.com/a/39485990/1938798) and the reference it links to more directly discusses the before/after the project() command issue. – Craig Scott Nov 19 '16 at 11:04
What is this `PROJECT` command and how to have this `cmake` option before it ? You would have an example ? – Stephane Feb 09 '19 at 14:33
`set(CMAKE_INSTALL_PREFIX "/usr" CACHE STRING " " FORCE )` , it's ok even if place it after `project()`. – kgbook Mar 05 '21 at 08:44

score 7 · Answer 3 · answered Jun 23 '16 at 18:40

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.

Try to use FORCE when you do SET: set (CMAKE_INSTALL_PREFIX /foo/bar/bubba CACHE PATH "Cmake prefix" FORCE) — Jav_Rock, Dec 22 '16 at 15:57

How to use CMAKE_INSTALL_PREFIX

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