создает сеанс и устанавливает идентификатор группы процессов (creates a session and sets the process group ID)
Имя (Name)
setsid - creates a session and sets the process group ID
Синопсис (Synopsis)
#include <unistd.h>
pid_t setsid(void);
Описание (Description)
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 (i.e., its session ID is made the same as its process
ID). The calling process also becomes the process group leader
of a new process group in the session (i.e., its process group ID
is made the same as its process ID).
The calling process will be the only process in the new process
group and in the new session.
Initially, the new session has no controlling terminal. For
details of how a session acquires a controlling terminal, see
credentials(7).
Возвращаемое значение (Return value)
On success, the (new) session ID of the calling process is
returned. On error, (pid_t) -1 is returned, and errno is set to
indicate the error.
Ошибки (Error)
EPERM The process group ID of any process equals the PID of the
calling process. Thus, in particular, setsid() fails if
the calling process is already a process group leader.
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008, SVr4.
Примечание (Note)
A child created via fork(2) inherits its parent's session ID.
The session ID is preserved across an execve(2).
A process group leader is a process whose process group ID equals
its PID. Disallowing a process group leader from calling
setsid() prevents the possibility that a process group leader
places itself in a new session while other processes in the
process group remain in the original session; such a scenario
would break the strict two-level hierarchy of sessions and
process groups. In order to be sure that setsid() will succeed,
call fork(2) and have the parent _exit(2), while the child (which
by definition can't be a process group leader) calls setsid().
If a session has a controlling terminal, and the CLOCAL flag for
that terminal is not set, and a terminal hangup occurs, then the
session leader is sent a SIGHUP signal.
If a process that is a session leader terminates, then a SIGHUP
signal is sent to each process in the foreground process group of
the controlling terminal.
Смотри также (See also)
setsid(1), getsid(2), setpgid(2), setpgrp(2), tcgetsid(3),
credentials(7), sched(7)
