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'\" te
.\" Copyright (c) 1989, AT&T. All rights reserved.
.\" Copyright (c) 2003, 2023, Oracle and/or its affiliates.
.TH semctl 2 "30 Jan 2023" "Oracle Solaris 11.4" "System Calls"
.SH NAME
semctl \- semaphore control operations
.SH SYNOPSIS

.LP
.nf
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>

\fBint\fR \fBsemctl\fR(\fBint\fR \fIsemid\fR, \fBint\fR \fIsemnum\fR, \fBint\fR \fIcmd\fR, ...);
.fi
.SH DESCRIPTION
.sp
.LP
The \fBsemctl()\fR function provides a variety of semaphore control operations as specified by \fIcmd\fR. The fourth argument is optional, depending upon the operation requested. If required, it is of type \fBunion semun\fR, which must be explicitly declared by the application program.
.sp
.in +2
.nf
union semun {
        int             val;
        struct semid_ds *buf;
        ushort_t        *array;
} arg;
.fi
.in -2
.sp
.sp
.LP
The permission required for a semaphore operation is given as {\fItoken\fR}, where \fItoken\fR is the type of permission needed. The types of permission are interpreted as follows:
.sp
.in +2
.nf
00400    READ by user
00200    ALTER by user
00040    READ by group
00020    ALTER by group
00004    READ by others
00002    ALTER by others
.fi
.in -2
.sp
.sp
.LP
See the \fBSemaphore Operation Permissions\fR subsection of the \fBDEFINITIONS\fR section of \fBIntro\fR(2) for more information.
.sp
.LP
The following semaphore operations may be specified by the \fIcmd\fR argument, to be executed with respect to the semaphore specified by \fIsemid\fR and \fIsemnum\fR.
.sp
.ne 2
.mk
.na
\fB\fBGETVAL\fR\fR
.ad
.RS 11n
.rt
Return the value of semval (see \fBIntro\fR(2)). {READ}
.RE

.sp
.ne 2
.mk
.na
\fB\fBSETVAL\fR\fR
.ad
.RS 11n
.rt
Set the value of \fBsemval\fR to \fIarg\fR.\fBval\fR. {ALTER} When this command is successfully executed, the \fBsemadj\fR value corresponding to the specified semaphore in all processes is cleared.
.RE

.sp
.ne 2
.mk
.na
\fB\fBGETPID\fR\fR
.ad
.RS 11n
.rt
Return the value of \fB(int) sempid\fR. {READ}
.RE

.sp
.ne 2
.mk
.na
\fB\fBGETNCNT\fR\fR
.ad
.RS 11n
.rt
Return the value of \fBsemncnt\fR. {READ}
.RE

.sp
.ne 2
.mk
.na
\fB\fBGETZCNT\fR\fR
.ad
.RS 11n
.rt
Return the value of \fBsemzcnt\fR. {READ}
.RE

.sp
.LP
The following operations return and set, respectively, every \fBsemval\fR in the set of semaphores.
.sp
.ne 2
.mk
.na
\fB\fBGETALL\fR\fR
.ad
.RS 10n
.rt
Place \fBsemval\fRs into array pointed to by \fIarg\fR.\fBarray\fR. {READ}
.RE

.sp
.ne 2
.mk
.na
\fB\fBSETALL\fR\fR
.ad
.RS 10n
.rt
Set \fBsemval\fRs according to the array pointed to by \fIarg\fR.\fBarray\fR. {ALTER}. When this cmd is successfully executed, the \fBsemadj\fR values corresponding to each specified semaphore in all processes are cleared.
.RE

.sp
.LP
The following operations are also available.
.sp
.ne 2
.mk
.na
\fB\fBIPC_STAT\fR\fR
.ad
.RS 12n
.rt
Place the current value of each member of the data structure associated with \fIsemid\fR into the structure pointed to by \fIarg\fR.\fBbuf\fR. The contents of this structure are defined in \fBIntro\fR(2). {READ}
.RE

.sp
.ne 2
.mk
.na
\fB\fBIPC_SET\fR\fR
.ad
.RS 12n
.rt
Set the value of the following members of the data structure associated with \fIsemid\fR to the corresponding value found in the structure pointed to by \fIarg\fR.\fBbuf\fR:
.sp
.sp
.in +2
.nf
sem_perm.uid
sem_perm.gid
sem_perm.mode	/* access permission bits only */
.fi
.in -2
.sp
This command can be executed only by a process that has either the {\fBPRIV_IPC_OWNER\fR} privilege or an effective user \fBID\fR equal to the value of \fBmsg_perm.cuid\fR or \fBmsg_perm.uid\fR in the data structure associated with \fImsqid\fR. Only a process with the {\fBPRIV_SYS_IPC_CONFIG\fR} privilege can raise the value of \fBmsg_qbytes\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBIPC_RMID\fR\fR
.ad
.RS 12n
.rt
Remove the semaphore identifier specified by \fIsemid\fR from the system and destroy the set of semaphores and data structure associated with it. This command can be executed only by a process that has the {\fBPRIV_IPC_OWNER\fR} privilege or an effective user \fBID\fR equal to the value of \fBsem_perm.cuid\fR or \fBsem_perm.uid\fR in the data structure associated with \fIsemid\fR.
.RE

.SH RETURN VALUES
.sp
.LP
Upon successful completion, the value returned depends on \fIcmd\fR as follows:
.sp
.ne 2
.mk
.na
\fB\fBGETVAL\fR\fR
.ad
.RS 11n
.rt
the value of \fBsemval\fR
.RE

.sp
.ne 2
.mk
.na
\fB\fBGETPID\fR\fR
.ad
.RS 11n
.rt
the value of \fB(int) sempid\fR
.RE

.sp
.ne 2
.mk
.na
\fB\fBGETNCNT\fR\fR
.ad
.RS 11n
.rt
the value of \fBsemncnt\fR
.RE

.sp
.ne 2
.mk
.na
\fB\fBGETZCNT\fR\fR
.ad
.RS 11n
.rt
the value of \fBsemzcnt\fR
.RE

.sp
.LP
All other successful completions return \fB0\fR; otherwise, \fB\(mi1\fR is returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBsemctl()\fR function will fail if:
.sp
.ne 2
.mk
.na
\fB\fBEACCES\fR\fR
.ad
.RS 13n
.rt
Operation permission is denied to the calling process (see \fBIntro\fR(2)).
.RE

.sp
.ne 2
.mk
.na
\fB\fBEFAULT\fR\fR
.ad
.RS 13n
.rt
The source or target is not a valid address in the user process.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 13n
.rt
The \fIsemid\fR argument is not a valid semaphore identifier; the \fIsemnum\fR argument is less than 0 or greater than (\fBsem_nsems\fR \(mi 1); or the \fIcmd\fR argument is not a valid command or is \fBIPC_SET\fR and \fBsem_perm.uid\fR or \fBsem_perm.gid\fR is not valid.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEPERM\fR\fR
.ad
.RS 13n
.rt
The \fIcmd\fR argument is equal to \fBIPC_RMID\fR or \fBIPC_SET\fR, the effective user ID of the calling process is not equal to the value of \fBsem_perm.cuid\fR or \fBsem_perm.uid\fR in the data structure associated with \fIsemid\fR, and {\fBPRIV_IPC_OWNER\fR} is not asserted in the effective set of the calling process.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEOVERFLOW\fR\fR
.ad
.RS 13n
.rt
The \fIcmd\fR argument is \fBIPC_STAT\fR and \fIuid\fR or \fIgid\fR is too large to be stored in the structure pointed to by \fIarg\fR.\fBbuf\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBERANGE\fR\fR
.ad
.RS 13n
.rt
The \fIcmd\fR argument is \fBSETVAL\fR or \fBSETALL\fR and the value to which \fBsemval\fR is to be set is greater than the system imposed maximum.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp
.TS
tab(
) box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPE
ATTRIBUTE VALUE
_
Interface Stability
Committed
_
Standard
See \fBstandards\fR(7).
.TE
.sp
.SH SEE ALSO
.sp
.LP
\fBipcs\fR(1), \fBIntro\fR(2), \fBsemget\fR(2), \fBsemop\fR(2), \fBstandards\fR(7), \fBattributes\fR(7), \fBprivileges\fR(7)
.SH HISTORY
.sp
.LP
The \fBsemctl()\fR function, including support for the \fBGETVAL\fR, \fBSETVAL\fR, \fBGETPID\fR, \fBGETNCNT\fR, \fBGETZCNT\fR, \fBGETALL\fR, \fBSETALL\fR, \fBIPC_STAT\fR, \fBIPC_SET\fR, and \fBIPC_RMID\fR operations, has been included in all Sun and Oracle releases of Solaris.