setsid(2)
setsid --
set session ID
Synopsis
#include <sys/types.h>
#include <unistd.h>
pid_t setsid(void);
Description
If the calling process is not already a process group leader, setsid sets the
process group ID and session ID of the calling process to the process ID of
the calling process, and releases the process's controlling terminal.
Return values
On success, setsid returns the calling process's session
ID.
On failure, setsid returns -1 and sets errno to identify the error.
Errors
In the following conditions, setsid fails and sets errno to:
- EPERM
-
The calling process is already a process group leader, or there are processes other
than the calling process whose process group ID is equal to the process ID
of the calling process.
References
exec(2),
exit(2),
fork(2),
getpid(2),
getsid(2),
intro(2),
setpgid(2),
setpgrp,
signal(2),
sigsend(2)
Notices
If the calling process is the last member of a pipeline started by a job
control shell, the shell may make the calling process a process group leader.
The other processes of the pipeline become members of that process group.
In this case, the call to setsid will fail.
For this reason, a
process that calls setsid and expects to be part of a pipeline
should always first fork; the parent should exit and the child should
call setsid, thereby insuring that the process will work reliably
when started by both job control shells and non-job control shells.
Considerations for threads programming
This ID number is an attribute of the containing process
and is shared by sibling threads.
30 January 1998
© 1998 The Santa Cruz Operation, Inc. All rights reserved.