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diff --git a/man-pages-posix-2017/man3p/semctl.3p b/man-pages-posix-2017/man3p/semctl.3p new file mode 100644 index 0000000..01709cf --- /dev/null +++ b/man-pages-posix-2017/man3p/semctl.3p @@ -0,0 +1,340 @@ +'\" et +.TH SEMCTL "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual" +.\" +.SH PROLOG +This manual page is part of the POSIX Programmer's Manual. +The Linux implementation of this interface may differ (consult +the corresponding Linux manual page for details of Linux behavior), +or the interface may not be implemented on Linux. +.\" +.SH NAME +semctl +\(em XSI semaphore control operations +.SH SYNOPSIS +.LP +.nf +#include\ <sys/sem.h> +.P +int semctl(int \fIsemid\fP, int \fIsemnum\fP, int \fIcmd\fP, ...); +.fi +.SH DESCRIPTION +The +\fIsemctl\fR() +function operates on XSI semaphores (see the Base Definitions volume of POSIX.1\(hy2017, +.IR "Section 4.17" ", " "Semaphore"). +It is unspecified whether this function interoperates with the +realtime interprocess communication facilities defined in +.IR "Section 2.8" ", " "Realtime". +.P +The +\fIsemctl\fR() +function provides a variety of semaphore control operations as +specified by +.IR cmd . +The fourth argument is optional and depends upon the operation +requested. If required, it is of type +.BR "union semun" , +which the application shall explicitly declare: +.sp +.RS 4 +.nf + +union semun { + int val; + struct semid_ds *buf; + unsigned short *array; +} arg; +.fi +.P +.RE +.P +Each operation shall be performed atomically. +.P +The following semaphore control operations as specified by +.IR cmd +are executed with respect to the semaphore specified by +.IR semid +and +.IR semnum . +The level of permission required for each operation is shown with each +command; see +.IR "Section 2.7" ", " "XSI Interprocess Communication". +The symbolic names for the values of +.IR cmd +are defined in the +.IR <sys/sem.h> +header: +.IP GETVAL 12 +Return the value of +.IR semval ; +see +.IR <sys/sem.h> . +Requires read permission. +.IP SETVAL 12 +Set the value of +.IR semval +to +.IR arg.val , +where +.IR arg +is the value of the fourth argument to +\fIsemctl\fR(). +When this command is successfully executed, the +.IR semadj +value corresponding to the specified semaphore in all processes is +cleared. Also, the +.IR sem_ctime +timestamp shall be set to the current time, as described in +.IR "Section 2.7.1" ", " "IPC General Description". +Requires alter permission; see +.IR "Section 2.7" ", " "XSI Interprocess Communication". +.IP GETPID 12 +Return the value of +.IR sempid . +Requires read permission. +.IP GETNCNT 12 +Return the value of +.IR semncnt . +Requires read permission. +.IP GETZCNT 12 +Return the value of +.IR semzcnt . +Requires read permission. +.P +The following values of +.IR cmd +operate on each +.IR semval +in the set of semaphores: +.IP GETALL 12 +Return the value of +.IR semval +for each semaphore in the semaphore set and place into the array +pointed to by +.IR arg.array , +where +.IR arg +is the fourth argument to +\fIsemctl\fR(). +Requires read permission. +.IP SETALL 12 +Set the value of +.IR semval +for each semaphore in the semaphore set according to the array pointed +to by +.IR arg.array , +where +.IR arg +is the fourth argument to +\fIsemctl\fR(). +When this command is successfully executed, the +.IR semadj +values corresponding to each specified semaphore in all processes are +cleared. Also, the +.IR sem_ctime +timestamp shall be set to the current time, as described in +.IR "Section 2.7.1" ", " "IPC General Description". +Requires alter permission. +.br +.P +The following values of +.IR cmd +are also available: +.IP IPC_STAT 12 +Place the current value of each member of the +.BR semid_ds +data structure associated with +.IR semid +into the structure pointed to by +.IR arg.buf , +where +.IR arg +is the fourth argument to +\fIsemctl\fR(). +The contents of this structure are defined in +.IR <sys/sem.h> . +Requires read permission. +.IP IPC_SET 12 +Set the value of the following members of the +.BR semid_ds +data structure associated with +.IR semid +to the corresponding value found in the structure pointed to by +.IR arg.buf , +where +.IR arg +is the fourth argument to +\fIsemctl\fR(): +.RS 12 +.sp +.RS 4 +.nf + +sem_perm.uid +sem_perm.gid +sem_perm.mode +.fi +.P +.RE +.P +The mode bits specified in +.IR "Section 2.7.1" ", " "IPC General Description" +are copied into the corresponding bits of the +.IR sem_perm.mode +associated with +.IR semid . +The stored values of any other bits are unspecified. The +.IR sem_ctime +timestamp shall be set to the current time, as described in +.IR "Section 2.7.1" ", " "IPC General Description". +.P +This command can only be executed by a process that has an effective +user ID equal to either that of a process with appropriate privileges +or to the value of +.IR sem_perm.cuid +or +.IR sem_perm.uid +in the +.BR semid_ds +data structure associated with +.IR semid . +.RE +.IP IPC_RMID 12 +Remove the semaphore identifier specified by +.IR semid +from the system and destroy the set of semaphores and +.BR semid_ds +data structure associated with it. This command can only be executed +by a process that has an effective user ID equal to either that of a +process with appropriate privileges or to the value of +.IR sem_perm.cuid +or +.IR sem_perm.uid +in the +.BR semid_ds +data structure associated with +.IR semid . +.SH "RETURN VALUE" +If successful, the value returned by +\fIsemctl\fR() +depends on +.IR cmd +as follows: +.IP GETVAL 12 +The value of +.IR semval . +.IP GETPID 12 +The value of +.IR sempid . +.IP GETNCNT 12 +The value of +.IR semncnt . +.IP GETZCNT 12 +The value of +.IR semzcnt . +.IP "All others" 12 +0. +.P +Otherwise, +\fIsemctl\fR() +shall return \-1 and set +.IR errno +to indicate the error. +.SH ERRORS +The +\fIsemctl\fR() +function shall fail if: +.TP +.BR EACCES +Operation permission is denied to the calling process; see +.IR "Section 2.7" ", " "XSI Interprocess Communication". +.TP +.BR EINVAL +The value of +.IR semid +is not a valid semaphore identifier, or the value of +.IR semnum +is less than 0 or greater than or equal to +.IR sem_nsems , +or the value of +.IR cmd +is not a valid command. +.TP +.BR EPERM +The argument +.IR cmd +is equal to IPC_RMID or IPC_SET +and the effective user ID of the calling process is not equal to that +of a process with appropriate privileges and it is not equal to the +value of +.IR sem_perm.cuid +or +.IR sem_perm.uid +in the data structure associated with +.IR semid . +.TP +.BR ERANGE +The argument +.IR cmd +is equal to SETVAL or SETALL and the value to which +.IR semval +is to be set is greater than the system-imposed maximum. +.LP +.IR "The following sections are informative." +.SH EXAMPLES +Refer to +.IR "\fIsemop\fR\^(\|)". +.SH "APPLICATION USAGE" +The fourth parameter in the SYNOPSIS section is now specified as +.BR \(dq...\(dq +in order to avoid a clash with the ISO\ C standard when referring to the union +.IR semun +(as defined in Issue 3) and for backwards-compatibility. +.P +The POSIX Realtime Extension defines alternative interfaces for interprocess +communication. Application developers who need to use IPC should +design their applications so that modules using the IPC routines +described in +.IR "Section 2.7" ", " "XSI Interprocess Communication" +can be easily modified to use the alternative interfaces. +.SH RATIONALE +None. +.SH "FUTURE DIRECTIONS" +None. +.SH "SEE ALSO" +.ad l +.IR "Section 2.7" ", " "XSI Interprocess Communication", +.IR "Section 2.8" ", " "Realtime", +.IR "\fIsemget\fR\^(\|)", +.IR "\fIsemop\fR\^(\|)", +.IR "\fIsem_close\fR\^(\|)", +.IR "\fIsem_destroy\fR\^(\|)", +.IR "\fIsem_getvalue\fR\^(\|)", +.IR "\fIsem_init\fR\^(\|)", +.IR "\fIsem_open\fR\^(\|)", +.IR "\fIsem_post\fR\^(\|)", +.IR "\fIsem_trywait\fR\^(\|)", +.IR "\fIsem_unlink\fR\^(\|)" +.ad b +.P +The Base Definitions volume of POSIX.1\(hy2017, +.IR "Section 4.17" ", " "Semaphore", +.IR "\fB<sys_sem.h>\fP" +.\" +.SH COPYRIGHT +Portions of this text are reprinted and reproduced in electronic form +from IEEE Std 1003.1-2017, Standard for Information Technology +-- Portable Operating System Interface (POSIX), The Open Group Base +Specifications Issue 7, 2018 Edition, +Copyright (C) 2018 by the Institute of +Electrical and Electronics Engineers, Inc and The Open Group. +In the event of any discrepancy between this version and the original IEEE and +The Open Group Standard, the original IEEE and The Open Group Standard +is the referee document. The original Standard can be obtained online at +http://www.opengroup.org/unix/online.html . +.PP +Any typographical or formatting errors that appear +in this page are most likely +to have been introduced during the conversion of the source files to +man page format. To report such errors, see +https://www.kernel.org/doc/man-pages/reporting_bugs.html . |