From 399644e47874bff147afb19c89228901ac39340e Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Mon, 15 Apr 2024 21:40:15 +0200 Subject: Adding upstream version 6.05.01. Signed-off-by: Daniel Baumann --- man3/sem_init.3 | 109 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 109 insertions(+) create mode 100644 man3/sem_init.3 (limited to 'man3/sem_init.3') diff --git a/man3/sem_init.3 b/man3/sem_init.3 new file mode 100644 index 0000000..5f9c352 --- /dev/null +++ b/man3/sem_init.3 @@ -0,0 +1,109 @@ +'\" t +.\" Copyright (C) 2006 Michael Kerrisk +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH sem_init 3 2023-07-20 "Linux man-pages 6.05.01" +.SH NAME +sem_init \- initialize an unnamed semaphore +.SH LIBRARY +POSIX threads library +.RI ( libpthread ", " \-lpthread ) +.SH SYNOPSIS +.nf +.B #include +.PP +.BI "int sem_init(sem_t *" sem ", int " pshared ", unsigned int " value ); +.fi +.SH DESCRIPTION +.BR sem_init () +initializes the unnamed semaphore at the address pointed to by +.IR sem . +The +.I value +argument specifies the initial value for the semaphore. +.PP +The +.I pshared +argument indicates whether this semaphore is to be shared +between the threads of a process, or between processes. +.PP +If +.I pshared +has the value 0, +then the semaphore is shared between the threads of a process, +and should be located at some address that is visible to all threads +(e.g., a global variable, or a variable allocated dynamically on +the heap). +.PP +If +.I pshared +is nonzero, then the semaphore is shared between processes, +and should be located in a region of shared memory (see +.BR shm_open (3), +.BR mmap (2), +and +.BR shmget (2)). +(Since a child created by +.BR fork (2) +inherits its parent's memory mappings, it can also access the semaphore.) +Any process that can access the shared memory region +can operate on the semaphore using +.BR sem_post (3), +.BR sem_wait (3), +and so on. +.PP +Initializing a semaphore that has already been initialized +results in undefined behavior. +.SH RETURN VALUE +.BR sem_init () +returns 0 on success; +on error, \-1 is returned, and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EINVAL +.I value +exceeds +.BR SEM_VALUE_MAX . +.TP +.B ENOSYS +.I pshared +is nonzero, +but the system does not support process-shared semaphores (see +.BR sem_overview (7)). +.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_init () +T} Thread safety MT-Safe +.TE +.sp 1 +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +POSIX.1-2001. +.PP +Bizarrely, POSIX.1-2001 does not specify the value that should +be returned by a successful call to +.BR sem_init (). +POSIX.1-2008 rectifies this, specifying the zero return on success. +.SH EXAMPLES +See +.BR shm_open (3) +and +.BR sem_wait (3). +.SH SEE ALSO +.BR sem_destroy (3), +.BR sem_post (3), +.BR sem_wait (3), +.BR sem_overview (7) -- cgit v1.2.3