# PR_OpenSemaphore

Creates or opens a named semaphore with the specified name.

## Syntax

```{code}
#include <pripcsem.h>

#define PR_SEM_CREATE 0x1 /* create if not exist */

#define PR_SEM_EXCL 0x2 /* fail if already exists */

NSPR_API(PRSem *) PR_OpenSemaphore(
  const char *name,
  PRIntn flags,
  PRIntn mode,
  PRUintn value
);
```

### Parameters

The function has the following parameters:

`name`

: The name to be given the semaphore.

`flags`

: How to create or open the semaphore.

`mode`

: Unix style file mode to be used when creating the semaphore.

`value`

: The initial value assigned to the semaphore.

### Returns

A pointer to a PRSem structure or `NULL/code> on error.`

### Description

If the named semaphore doesn't exist and the `PR_SEM_CREATE` flag is
specified, the named semaphore is created. The created semaphore needs
to be removed from the system with a {ref}`PR_DeleteSemaphore` call.

If `PR_SEM_CREATE` is specified, the third argument is the access
permission bits of the new semaphore (same interpretation as the mode
argument to {ref}`PR_Open`) and the fourth argument is the initial value of
the new semaphore. `If PR_SEM_CREATE` is not specified, the third and
fourth arguments are ignored.