# %semctl() function

The %semctl() function performs semaphore
control operations.

**For Windows:**Not Supported

## Syntax

```
code = %semctl(sem-ID, semnum, cmd, arg)
```

## Parameter(s)

| sem-ID | Semaphore ID returned by a call to %semget(). |
| --- | --- |
| semnum | Semaphore number in the set, when applicable (depending on cmd). |
| cmd | Valid values for cmd are defined in sem.h and ipc.h. The commands below are executed with respect to the semaphore specified by sem-ID and semnum: |
| getval | Returns the value of semval. |
| setval | Sets semval to the value of arg. |
| getpid | Returns the value of sempid. |
| getncnt | Returns the value of semncnt. |
| getzcnt | Returns the value of semzcnt. |
| The commands below apply to all semaphores in the set: | |
| getall | Place all the semaphore values in the arg dimensioned array. |
| setall | Set all the semaphores to the values contained in the dimensioned array arg. |
| These commands are also available: | |
| ipc$stat | Return a dimensioned array that contains the various fields of the UNIX semaphore structures. The elements are (see the UNIX system documentation): |
| 1 sem_perm.uid | |
| 2 sem_perm.cid | |
| 3 sem_perm.guid | |
| 4 sem_perm.gcid | |
| 5 sem_perm.mode | |
| 6 sem_perm.seq | |
| 7 sem_perm.key | |
| 8 sem_nsems | |
| 9 sem_otime | |
| 10 sem_ctime | |
| ipc$set | Sets the values of the below members of the data structure associated to sem-ID to the first three elements of the array arg: |
| 1 sem_perm.uid | |
| 2 sem_perm.gid | |
| 3 sem_perm.mode | |
| ipc$rmid | Removes the semaphore identifier. |
| arg | Dimensioned array that contains the argument. |

## Example(s)

```
include dm,bp,unix.h ipc.h
include dm,bp,unix.h sem.h
* Set initial semaphore values
dim val(3)
mat val=0
%semctl(sem-ID, 0, setall, val)
```

## See also

- [%semget() function](https://d3codex.com/pickbasic-flashbasic/percent-semget-function/)
- [%semop() function](https://d3codex.com/pickbasic-flashbasic/percent-semop-function/)
- [FlashBASIC C functions overview](https://d3codex.com/pickbasic-flashbasic/flashbasic-c-functions-overview/)
- [cfunction statement](https://d3codex.com/pickbasic-flashbasic/cfunction-statement/)

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Source: https://d3codex.com/pickbasic-flashbasic/percent-semctl-function/ - part of the D3Codex reference.