SEMCTL(2) BSD System Calls Manual SEMCTL(2)

NAME
     sseemmccttll - control operations on a semaphore set

SYNOPSIS
     ##iinncclluuddee <>

     int
     sseemmccttll(int semid, int semnum, int cmd, ...);

DESCRIPTION
     The sseemmccttll() system call performs the operation indicated by cmd on the
     semaphore set indicated by semid.  A fourth argument, a union semun arg,
     is required for certain values of cmd.  For the commands that use the arg
     argument, union semun is defined as follows:

     union semun {
             int     val;            /* value for SETVAL */
             struct  semidds *buf;  /* buffer for IPCSTAT & IPCSET */
             ushort *array;         /* array for GETALL & SETALL */
     };

     Commands are performed as follows:

     IPCSTAT     Fetch the semaphore set's struct semidds, storing it in the
                  memory pointed to by arg.buf.

     IPCSET      Changes the semperm.uid, semperm.gid, and semperm.mode
                  members of the semaphore set's struct semidds to match
                  those of the struct pointed to by arg.buf.  The calling
                  process's effective uid must match either semperm.uid or
                  semperm.cuid, or it must have superuser privileges.

     IPCRMID     Immediately removes the semaphore set from the system.  The
                  calling process's effective uid must equal the semaphore
                  set's semperm.uid or semperm.cuid, or the process must
                  have superuser privileges.

     GETVAL       Return the value of semaphore number semnum.

     SETVAL       Set the value of semaphore number semnum to arg.val.  Out-
                  standing adjust on exit values for this semaphore in any
                  process are cleared.

     GETPID       Return the pid of the last process to perform an operation
                  on semaphore number semnum.

     GETNCNT      Return the number of processes waiting for semaphore number
                  semnum's value to become greater than its current value.

     GETZCNT      Return the number of processes waiting for semaphore number
                  semnum's value to become 0.

     GETALL       Fetch the value of all of the semaphores in the set into the
                  array pointed to by arg.array.

     SETALL       Set the values of all of the semaphores in the set to the
                  values in the array pointed to by arg.array.  Outstanding
                  adjust on exit values for all semaphores in this set, in any
                  process are cleared.

     The struct semidds is defined as follows:

     struct semidds {
             struct  ipcperm semperm;      /* operation permission struct */
             struct  sem *sembase;  /* pointer to first semaphore in set */
             ushort semnsems;      /* number of sems in set */
             timet  semotime;      /* last operation time */
             long    sempad1;       /* SVABI/386 says I need this here */
             timet  semctime;      /* last change time */
                                     /* Times measured in secs since */
                                     /* 00:00:00 GMT, Jan. 1, 1970 */
             long    sempad2;       /* SVABI/386 says I need this here */
             long    sempad3[4];    /* SVABI/386 says I need this here */
     };

RETURN VALUES
     On success, when cmd is one of GETVAL, GETPID, GETNCNT or GETZCNT,
     sseemmccttll() returns the corresponding value; otherwise, 0 is returned.  On
     failure, -1 is returned, and errno is set to indicate the error.

EERRRROORRSS
     The sseemmccttll() system call will fail if:

     [EACCES]           Permission denied due to mismatch between operation
                        and mode of semaphore set.

     [EINVAL]           No semaphore set corresponds to semid.

     [EINVAL]           The semnum argument is not in the range of valid sema-
                        phores for given semaphore set.

     [EPERM]            The calling process's effective uid does not match the
                        uid of the semaphore set's owner or creator.

     [ERANGE]           SETVAL or SETALL attempted to set a semaphore outside
                        the allowable range [0 .. SEMVMX].

LEGACY SYNOPSIS
     ##iinncclluuddee <>
     ##iinncclluuddee <>
     ##iinncclluuddee <>

     The include files  and  are necessary.

SEE ALSO
     semget(2), semop(2), compat(5)

BUGS
     SETALL may update some semaphore elements before returning an error.

BSD                           September 12, 1995                           BSD