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'\" et
.TH SEM_UNLINK "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
sem_unlink
\(em remove a named semaphore
.SH SYNOPSIS
.LP
.nf
#include <semaphore.h>
.P
int sem_unlink(const char *\fIname\fP);
.fi
.SH DESCRIPTION
The
\fIsem_unlink\fR()
function shall remove the semaphore named by the string
.IR name .
If the semaphore named by
.IR name
is currently referenced by other processes, then
\fIsem_unlink\fR()
shall have no effect on the state of the semaphore. If one or more
processes have the semaphore open when
\fIsem_unlink\fR()
is called, destruction of the semaphore is postponed until all
references to the semaphore have been destroyed by calls to
\fIsem_close\fR(),
\fI_exit\fR(),
or
.IR exec .
Calls to
\fIsem_open\fR()
to recreate or reconnect to the semaphore refer to a new semaphore
after
\fIsem_unlink\fR()
is called. The
\fIsem_unlink\fR()
call shall not block until all references have been destroyed; it
shall return immediately.
.SH "RETURN VALUE"
Upon successful completion, the
\fIsem_unlink\fR()
function shall return a value of 0. Otherwise, the semaphore shall not
be changed and the function shall return a value of \-1 and set
.IR errno
to indicate the error.
.SH ERRORS
The
\fIsem_unlink\fR()
function shall fail if:
.TP
.BR EACCES
Permission is denied to unlink the named semaphore.
.TP
.BR ENOENT
The named semaphore does not exist.
.P
The
\fIsem_unlink\fR()
function may fail if:
.TP
.BR ENAMETOOLONG
.br
The length of the
.IR name
argument exceeds
{_POSIX_PATH_MAX}
on systems that do not support the XSI option
or exceeds
{_XOPEN_PATH_MAX}
on XSI systems,
or has a pathname component that is longer than
{_POSIX_NAME_MAX}
on systems that do not support the XSI option
or longer than
{_XOPEN_NAME_MAX}
on XSI systems.
A call to
\fIsem_unlink\fR()
with a
.IR name
argument that contains the same semaphore name as was previously used
in a successful
\fIsem_open\fR()
call shall not give an
.BR [ENAMETOOLONG]
error.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
A future version might require the
\fIsem_open\fR()
and
\fIsem_unlink\fR()
functions to have semantics similar to normal file system operations.
.SH "SEE ALSO"
.IR "\fIsemctl\fR\^(\|)",
.IR "\fIsemget\fR\^(\|)",
.IR "\fIsemop\fR\^(\|)",
.IR "\fIsem_close\fR\^(\|)",
.IR "\fIsem_open\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<semaphore.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 .
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