Started with asio tutorial from boost 1.35. Copied the second timer code but cannot compile it. In the same setting, I compiled and run an example from boost. Following is the first 3 errors: g++ -g -Wall -I. -I./include -I/home/lmei/work/boostlib/boost_1_35_0 ./timer.cpp -o timer /tmp/ccKOni8q.o: In function `__static_initialization_and_destruction_0':/home/lmei/work/boostlib/boost_1_35_0/boost/system/error_code.hpp:204: undefined reference to `boost::system::get_system_category()' :/home/lmei/work/boostlib/boost_1_35_0/boost/system/error_code.hpp:205: undefined reference to `boost::system::get_posix_category()' :/home/lmei/work/boostlib/boost_1_35_0/boost/system/error_code.hpp:209: undefined reference to `boost::system::get_posix_category()' :/home/lmei/work/boostlib/boost_1_35_0/boost/system/error_code.hpp:210: undefined reference to `boost::system::get_system_category()' please help. thanks