It is the last example in <<APUE>>, and also a good example for myself.

#------------------------------------------------------------
fileName : public_function.h  
describe : contains the functions that used in common

(1)error : send error message then exit;
(2)sig_chld : deal with the signal SIGCHLD;
(3)getAddrInfo : get the IP address informaion of host;
(4)scanConfigFile : read the key-value pair;
(5)readn : read n bytes;
(6)writen : write n bytes;

#------------------------------------------------------------
fileName : print.h
describe : the declaration of Print

#------------------------------------------------------------
fileName : print.cpp
describe : the definition of Print

#------------------------------------------------------------
fileName : print_daemon.h
describe : the definition of PrintDaemon

#------------------------------------------------------------
fileName : print_daemon.cpp
describe : the definition of PrintDaemon