'\" te
.\" Copyright (c) 2006, Sun Microsystems, Inc.  All Rights Reserved.
.\" Copyright 1989 AT&T
.TH semget 2 "14 Aug 2006" "SunOS 5.11" "System Calls"
.SH NAME
semget \- get set of semaphores
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>

\fBint\fR \fBsemget\fR(\fBkey_t\fR \fIkey\fR, \fBint\fR \fInsems\fR, \fBint\fR \fIsemflg\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBsemget()\fR function returns the semaphore identifier associated with \fIkey\fR.
.sp
.LP
A semaphore identifier and associated data structure and set containing \fInsems\fR semaphores (see \fBIntro\fR(2)) are created for \fIkey\fR if one of the following is true:
.RS +4
.TP
.ie t \(bu
.el o
\fIkey\fR is equal to \fBIPC_PRIVATE\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fIkey\fR does not already have a semaphore identifier associated with it, and (\fIsemflg\fR\fB&IPC_CREAT\fR) is true.
.RE
.sp
.LP
On creation, the data structure associated with the new semaphore identifier is initialized as follows:
.RS +4
.TP
.ie t \(bu
.el o
\fBsem_perm.cuid\fR, \fBsem_perm.uid\fR, \fBsem_perm.cgid\fR, and \fBsem_perm.gid\fR are set equal to the effective user \fBID\fR and effective group \fBID,\fR respectively, of the calling process.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The access permission bits of \fBsem_perm.mode\fR are set equal to the access permission bits of \fIsemflg\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fBsem_nsems\fR is set equal to the value of \fInsems\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fBsem_otime\fR is set equal to 0 and \fBsem_ctime\fR is set equal to the current time.
.RE
.SH RETURN VALUES
.sp
.LP
Upon successful completion, a non-negative integer representing a semaphore identifier is returned. Otherwise, \fB\(mi1\fR is returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBsemget()\fR function will fail if:
.sp
.ne 2
.mk
.na
\fB\fBEACCES\fR\fR
.ad
.RS 10n
.rt  
A semaphore identifier exists for \fIkey\fR, but operation permission (see \fBIntro\fR(2)) as specified by the low-order 9 bits of \fIsemflg\fR would not be granted.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEEXIST\fR\fR
.ad
.RS 10n
.rt  
A semaphore identifier exists for \fIkey\fR but both (\fIsemflg\fR\fB&IPC_CREAT\fR) and (\fIsemflg\fR\fB&IPC_EXCL\fR) are both true.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
.rt  
The \fInsems\fR argument is either less than or equal to 0 or greater than the system-imposed limit. See NOTES.
.sp
A semaphore identifier exists for \fIkey\fR, but the number of semaphores in the set associated with it is less than \fInsems\fR and \fInsems\fR is not equal to 0.
.RE

.sp
.ne 2
.mk
.na
\fB\fBENOENT\fR\fR
.ad
.RS 10n
.rt  
A semaphore identifier does not exist for \fIkey\fR and (\fIsemflg\fR\fB&IPC_CREAT\fR) is false.
.RE

.sp
.ne 2
.mk
.na
\fB\fBENOSPC\fR\fR
.ad
.RS 10n
.rt  
A semaphore identifier is to be created but the system-imposed limit on the maximum number of allowed semaphores or semaphore identifiers system-wide would be exceeded. See NOTES.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
StandardSee \fBstandards\fR(5).
.TE

.SH SEE ALSO
.sp
.LP
\fBipcrm\fR(1), \fBipcs\fR(1), \fBrctladm\fR(1M), \fBIntro\fR(2), \fBsemctl\fR(2), \fBsemop\fR(2), \fBsetrctl\fR(2), \fBftok\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)
.SH NOTES
.sp
.LP
The system-imposed limit on the value of the \fInsems\fR argument is the maintained on a per-process basis using the \fBprocess.max-sem-nsems\fR resource control.
.sp
.LP
The system-imposed limit on the number of semaphore identifiers is maintained on a per-project basis using the \fBproject.max-sem-ids\fR resource control. The  \fBzone.max-sem-ids\fR resource control limis the total number of semaphore identifiers that can be allocated by a zone.
.sp
.LP
See \fBrctladm\fR(1M) and \fBsetrctl\fR(2) for information about using resource controls.