# target_include_directories

Add include directories to a target.

    target_include_directories(<target> [SYSTEM] [BEFORE]
      <INTERFACE|PUBLIC|PRIVATE> [items1...]
      [<INTERFACE|PUBLIC|PRIVATE> [items2...] ...])

Specify include directories to use when compiling a given target. The named `<target>` must have been created by a command such as `add_executable()` or `add_library()` and must not be an ALIAS target.

If `BEFORE` is specified, the content will be prepended to the property instead of being appended.

The `INTERFACE`, `PUBLIC` and `PRIVATE` keywords are required to specify the scope of the following arguments. `PRIVATE` and `PUBLIC` items will populate the `INCLUDE_DIRECTORIES` property of `<target>`. `PUBLIC` and `INTERFACE` items will populate the `INTERFACE_INCLUDE_DIRECTORIES` property of `<target>`. (IMPORTED targets only support `INTERFACE` items.) The following arguments specify include directories.

Specified include directories may be absolute paths or relative paths. Repeated calls for the same <target> append items in the order called. If `SYSTEM` is specified, the compiler will be told the directories are meant as system include directories on some platforms (signalling this setting might achieve effects such as the compiler skipping warnings, or these fixed-install system files not being considered in dependency calculations - see compiler docs). If `SYSTEM` is used together with `PUBLIC` or `INTERFACE`, the `INTERFACE_SYSTEM_INCLUDE_DIRECTORIES` target property will be populated with the specified directories.

Arguments to `target_include_directories` may use “generator expressions” with the syntax `$<...>`. See the `cmake-generator-expressions(7)` manual for available expressions. See the `cmake-buildsystem(7)` manual for more on defining buildsystem properties.

Include directories usage requirements commonly differ between the build-tree and the install-tree. The `BUILD_INTERFACE` and `INSTALL_INTERFACE` generator expressions can be used to describe separate usage requirements based on the usage location. Relative paths are allowed within the `INSTALL_INTERFACE` expression and are interpreted relative to the installation prefix. For example:

    target_include_directories(mylib PUBLIC
      $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include/mylib>
      $<INSTALL_INTERFACE:include/mylib>  # <prefix>/include/mylib
    )

## Creating Relocatable Packages

Note that it is not advisable to populate the `INSTALL_INTERFACE` of the `INTERFACE_INCLUDE_DIRECTORIES` of a target with absolute paths to the include directories of dependencies. That would hard-code into installed packages the include directory paths for dependencies as found on the machine the package was made on.

The `INSTALL_INTERFACE` of the `INTERFACE_INCLUDE_DIRECTORIES` is only suitable for specifying the required include directories for headers provided with the target itself, not those provided by the transitive dependencies listed in its `INTERFACE_LINK_LIBRARIES` target property. Those dependencies should themselves be targets that specify their own header locations in `INTERFACE_INCLUDE_DIRECTORIES`.

See the Creating Relocatable Packages section of the `cmake-packages(7)` manual for discussion of additional care that must be taken when specifying usage requirements while creating packages for redistribution.