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(5) 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(5), standards(5)

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)