# Unknown CMake command "generate\_export\_header"
**URL:** https://discourse.cmake.org/t/unknown-cmake-command-generate-export-header/3536
**Category:** Usage
**Tags:** comp:mingw, comp:msvc, os:windows
**Created:** [June 9, 2021, 6:08am UTC](https://discourse.cmake.org/t/unknown-cmake-command-generate-export-header/3536 "2021-06-09T06:08:16Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Alkexan](https://discourse.cmake.org/u/Alkexan)
#### Post date: [June 9, 2021, 6:08am UTC](https://discourse.cmake.org/t/unknown-cmake-command-generate-export-header/3536/1 "2021-06-09T06:08:16Z")
Hi, I’m trying to make .dll, and I wrote this CMakeFile.txt:
```auto
# Shared Library CMakeList.txt
cmake_minimum_required (VERSION 3.12)
# Set language and the project name
project (mylib CXX)
# add all source files from directories
aux_source_directory("../src" MYLIB_SRC)
# compile library
add_library(mylib SHARED ${MYLIB_SRC})
generate_export_header(mylib)
# add include files
target_include_directories(mylib PUBLIC "../src")
```
And I want use [generate\_export\_header](https://cmake.org/cmake/help/latest/module/GenerateExportHeader.html) for generation of export macros for library, but I have this error:
> Unknown CMake command “generate\_export\_header”
Cmake version 3.20.3.
---
### Author:  [@fenrir](https://discourse.cmake.org/u/fenrir)
#### Post date: [June 9, 2021, 6:39am UTC](https://discourse.cmake.org/t/unknown-cmake-command-generate-export-header/3536/2 "2021-06-09T06:39:25Z")
`GenerateExportHeader` is a module that has to be included, so
```auto
...
include(GenerateExportHeader)
generate_export_header(mylib)
...
```
---
### Author:  [@Alkexan](https://discourse.cmake.org/u/Alkexan)
#### Post date: [June 9, 2021, 7:02am UTC](https://discourse.cmake.org/t/unknown-cmake-command-generate-export-header/3536/3 "2021-06-09T07:02:05Z")
Thank you very much