4.2. AC_CHECK_LIB

AC_CHECK_LIB checks for a presence of a symbol inside a library.
It can run optional shell codes, (accepted as the third and fourth arguments) if it succeeds or fails.
If it succeeds it will prepend -l[library] to compiler flags, and define the preprocessor macro HAVE_LIB[library].
Examples:

AC_CHECK_LIB(m, pow)

if test "x$requires_libavl" = "xyes" ; then
    AC_CHECK_LIB(avl, avl_create, [], [
        echo "Error! You need to have libavl around."
        exit -1
        ])
fi