2008 May 30 Friday (五月 三十日 金曜日)

#include <unistd.h>   pid_t setsid(void);     setsid()  creates  a new session if the calling process is not a process group leader.  The calling process is the leader of the new session, the process group leader of the new process group, and has no controlling tty.  The process group ID and session ID of the calling process are set to the PID of the calling process.  The calling process will be the only process in this new process group and in this new session.   #include <unistd.h>   pid_t tcgetpgrp(int fd);   int tcsetpgrp(int fd, pid_t pgrp);   The function tcgetpgrp() returns the process group ID of the foreground process group on the terminal associated to fd, which must be the controlling terminal of the calling process.   The function tcsetpgrp() makes the process group with process group ID pgrp the foreground process group on the terminal associated to fd, which must be the controlling terminal of the calling process, and still be associated with its session. Moreover, pgrp must be a (nonempty) process group belonging to the same session as the calling process.   If tcsetpgrp() is called by a member of a background process group in its session, and the calling process is not blocking or ignoring SIGTTOU, a SIGTTOU signal is sent to all members of this background process group.