Hello, The following command assigns the variable OPENCV_CFLAGS with "-I /path/to/opencv/include": PKG_CHECK_MODULES(OPENCV, opencv >= 2.3.1,, AC_MSG_ERROR(${OPENCV_PKG_ERRORS})) Q1: How to I tell AC_CHECK_HEADER to use the include directory specified in OPENCV_CFLAGS? A1: CPPFLAGS="${OPENCV_CFLAGS} $CPPFLAGS" Q2: But I thought I wasn't supposed to mess with CPPFLAGS, it was only for the user to play with. Plus I don't want to affect all CPPFLAGS for the entire project. I intend to selectively apply OPENCV_CFLAGS where needed. A2: That's not a question. Thank you, Chris _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx https://lists.gnu.org/mailman/listinfo/autoconf