freopen造句

• In Unix-like operating systems, programs do redirection with the dup2 ( 2 ) system call, or its less-flexible but higher-level stdio analogues, freopen ( 3 ) and popen ( 3 ).
• A process itself can change what these ( often by calling freopen ) but changing another process'( p ) ttys isn't easy; there isn't a kernel call to do this ( but more later ).