# CheckIncludeFile

Provides a macro to check if a header file can be included in `C`.

`CHECK_INCLUDE_FILE`

      CHECK_INCLUDE_FILE(<include> <variable> [<flags>])

  Check if the given `<include>` file may be included in a `C` source file and store the result in an internal cache entry named `<variable>`. The optional third argument may be used to add compilation flags to the check (or use `CMAKE_REQUIRED_FLAGS` below).

The following variables may be set before calling this macro to modify the way the check is run:

`CMAKE_REQUIRED_FLAGS`

  string of compile command line flags.

`CMAKE_REQUIRED_DEFINITIONS`

  a ;-list of macros to define (-DFOO=bar).

`CMAKE_REQUIRED_INCLUDES`

  a ;-list of header search paths to pass to the compiler.

`CMAKE_REQUIRED_LINK_OPTIONS`

  a ;-list of options to add to the link command.

`CMAKE_REQUIRED_LIBRARIES`

  a ;-list of libraries to add to the link command. See policy `CMP0075`.

`CMAKE_REQUIRED_QUIET`

  execute quietly without messages.

See the `CheckIncludeFiles` module to check for multiple headers at once. See the `CheckIncludeFileCXX` module to check for headers using the `CXX` language.