'\" t .\" Copyright (C) 2006 Michael Kerrisk .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .TH sem_close 3 2024-05-02 "Linux man-pages 6.9.1" .SH NAME sem_close \- close a named semaphore .SH LIBRARY POSIX threads library .RI ( libpthread ", " \-lpthread ) .SH SYNOPSIS .nf .B #include .P .BI "int sem_close(sem_t *" sem ); .fi .SH DESCRIPTION .BR sem_close () closes the named semaphore referred to by .IR sem , allowing any resources that the system has allocated to the calling process for this semaphore to be freed. .SH RETURN VALUE On success .BR sem_close () returns 0; on error, \-1 is returned, with .I errno set to indicate the error. .SH ERRORS .TP .B EINVAL .I sem is not a valid semaphore. .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .TS allbox; lbx lb lb l l l. Interface Attribute Value T{ .na .nh .BR sem_close () T} Thread safety MT-Safe .TE .SH STANDARDS POSIX.1-2008. .SH HISTORY POSIX.1-2001. .SH NOTES All open named semaphores are automatically closed on process termination, or upon .BR execve (2). .SH SEE ALSO .BR sem_getvalue (3), .BR sem_open (3), .BR sem_post (3), .BR sem_unlink (3), .BR sem_wait (3), .BR sem_overview (7)