SETSID(2) System Calls SETSID(2)

NAME

setsid - create session and set process group ID

SYNOPSIS

#include <sys/types.h>
#include <unistd.h>

pid_t setsid(void);

DESCRIPTION

The setsid() function creates a new session, if the calling process
is not a process group leader. Upon return the calling process will
be the session leader of this new session, will be the process group
leader of a new process group, and will have no controlling terminal.
The process group ID of the calling process will be set equal to the
process ID of the calling process. The calling process will be the
only process in the new process group and the only process in the new
session.

RETURN VALUES

Upon successful completion, setsid() returns the value of the process
group ID of the calling process. Otherwise it returns (pid_t)-1 and
sets errno to indicate the error.

ERRORS

The setsid() function will fail if:

EPERM
The calling process is already a process group leader, or
the process group ID of a process other than the calling
process matches the process ID of the calling process.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Standard |
+--------------------+-------------------+
|MT-Level | Async-Signal-Safe |
+--------------------+-------------------+

SEE ALSO

getsid(2), setpgid(2), setpgrp(2), attributes(7), standards(7)

WARNINGS

A call to setsid() by a process that is a process group leader will
fail. A process can become a process group leader by being the last
member of a pipeline started by a job control shell. Thus, a process
that expects to be part of a pipeline, and that calls setsid(),
should always first fork; the parent should exit and the child should
call setsid(). This will ensure that the calling process will work
reliably when started by both job control shells and non-job control
shells.

August 21, 2002 SETSID(2)