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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-24 04:52:24 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-24 04:52:24 +0000 |
commit | 100d1b33f088fd38f69129afff7f9c2a1e084a57 (patch) | |
tree | 5bf6b0bb14f22ecf0a5e9439fdd4c4758402400c /man/man3/sem_init.3 | |
parent | Releasing progress-linux version 6.7-2~progress7.99u1. (diff) | |
download | manpages-100d1b33f088fd38f69129afff7f9c2a1e084a57.tar.xz manpages-100d1b33f088fd38f69129afff7f9c2a1e084a57.zip |
Merging upstream version 6.8.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'man/man3/sem_init.3')
-rw-r--r-- | man/man3/sem_init.3 | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/man/man3/sem_init.3 b/man/man3/sem_init.3 new file mode 100644 index 0000000..8ea6b64 --- /dev/null +++ b/man/man3/sem_init.3 @@ -0,0 +1,108 @@ +'\" t +.\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH sem_init 3 2024-05-02 "Linux man-pages (unreleased)" +.SH NAME +sem_init \- initialize an unnamed semaphore +.SH LIBRARY +POSIX threads library +.RI ( libpthread ", " \-lpthread ) +.SH SYNOPSIS +.nf +.B #include <semaphore.h> +.P +.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. +.P +The +.I pshared +argument indicates whether this semaphore is to be shared +between the threads of a process, or between processes. +.P +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). +.P +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. +.P +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 +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +POSIX.1-2001. +.P +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) |