# CMAKE\_SYSTEM\_INCLUDE\_PATH - has just one path, for X11?

**URL:** <https://discourse.cmake.org/t/cmake-system-include-path-has-just-one-path-for-x11/2060>\
**Category:** Code\
**Created:** [October 23, 2020, 10:42pm UTC](https://discourse.cmake.org/t/cmake-system-include-path-has-just-one-path-for-x11/2060 "2020-10-23T22:42:46Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![tomoreilly](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/t/439d5e/32.png) [@tomoreilly](https://discourse.cmake.org/u/tomoreilly)\
**Post date:** [October 23, 2020, 10:42pm UTC](https://discourse.cmake.org/t/cmake-system-include-path-has-just-one-path-for-x11/2060/1 "2020-10-23T22:42:46Z")

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Running on Ubuntu 18.04, cmake version 3.18.0-rc2. From [documentation](https://cmake.org/cmake/help/latest/variable/CMAKE_SYSTEM_INCLUDE_PATH.html) I expect CMAKE\_SYSTEM\_INCLUDE\_PATH to hold a list of directories including /usr/include, /usr/local/include, etc. :

```auto
Semicolon-separated list of directories specifying a search path for the find_file() and find_path() commands. By default this contains the standard directories for the current system.

```

However when I print the value of CMAKE\_SYSTEM\_INCLUDE\_PATH from my CMakeLists.txt I get:

```auto
CMAKE_SYSTEM_INCLUDE_PATH: /usr/include/X11

```

Why is this? Thanks!

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**Author:** ![ben.boeckel](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)\
**Post date:** [November 25, 2020, 12:25am UTC](https://discourse.cmake.org/t/cmake-system-include-path-has-just-one-path-for-x11/2060/2 "2020-11-25T00:25:54Z")

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@brad.king

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<div class="post-metadata">

**Author:** ![brad.king](https://discourse.cmake.org/user_avatar/discourse.cmake.org/brad.king/32/11_2.png) [@brad.king](https://discourse.cmake.org/u/brad.king)\
**Post date:** [November 25, 2020, 12:24pm UTC](https://discourse.cmake.org/t/cmake-system-include-path-has-just-one-path-for-x11/2060/3 "2020-11-25T12:24:09Z")

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It’s historical. Most of the paths that were once in `CMAKE_SYSTEM_INCLUDE_PATH` are now handled by `CMAKE_SYSTEM_PREFIX_PATH`. Note that these values are meant for the `find_*` commands and are not supposed to represent the compiler’s implicit include directories or anything like that.