HP-UX Reference (11i v3 07/02) - 2 System Calls (vol 5)

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sem_unlink(2) sem_unlink(2)

NAME

sem_unlink - unlink a named POSIX semaphore

SYNOPSIS

#include <sys/semaphore.h>

int sem_unlink(const char *name);

DESCRIPTION

sem_unlink() is used to unlink named semaphores. A successful call to

sem_unlink() marks the

semaphore, speciﬁed by name, for removal. Calling

sem_unlink() does not affect processes, including

the calling process, which currently have a descriptor, obtained from a call to

sem_open() . Named

semaphores are uniquely identiﬁed by character strings. All character string names will be pre-processed

to ensure variations of a pathname resolve to the same semaphore name. If the semaphore is successfully

marked for removal by a call to

sem_unlink()

, the semaphore will be removed when all processes

remove their descriptors to the speciﬁed semaphore by calling

sem_close() . Subsequent calls to

sem_open() using the string name will refer to a new semaphore.

To use this function, link in the realtime library by specifying -lrt on the compiler or linker command

line.

EXAMPLES

The following call to sem_unlink() will remove the named semaphore named by the string name.If

the semaphore is currently referenced by one or more processes, the semaphore will be marked for removal

and removed when there are no more processes referencing it.

sem_unlink(name);

RETURN VALUE

If the semaphore was unlinked successfully,

sem_unlink() returns 0.

If the semaphore could not be unlinked, the call returns -1 and sets

errno to indicate the error.

ERRORS

sem_unlink() fails and does not perform the requested operation if any of the following conditions are

encountered:

[EACCES] The named semaphore exists and the process does not have the permissions to unlink

the semaphore.

[ENAMETOOLONG]

The name string is longer than {PATH_MAX} .

[ENOENT] The ﬂag O_CREAT is not set in oﬂag (see sem_open(2)) and the named semaphore

does not exist.