Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #198
Difficulty: Easy
Bash ranked in the top 20 programming languages according to the TIOBE Index for October 2019.
True or False?
Linux & Unix Commands - Search Man Pages

sem_unlink(3) [osf1 man page]

sem_unlink(3)						     Library Functions Manual						     sem_unlink(3)

sem_unlink - Removes the specified named semaphore (P1003.1b) LIBRARY
Realtime Library (, librt.a) SYNOPSIS
#include <semaphore.h> int sem_unlink ( const char *name) ; PARAMETERS
*name Specifies the name of the semaphore to remove. DESCRIPTION
The sem_unlink function removes a semaphore named by the string name. If the semaphore is referenced by other processes, sem_unlink does not change the state of the semaphore. If other processes have the semaphore open when sem_unlink is called, the semaphore is not destroyed until all references to the semaphore have been destroyed by calls to sem_close. The sem_unlink function returns immediately; it does not wait until all references have been destroyed. Calls to sem_open to recreate or reconnect to the semaphore refer to a new semaphore after sem_unlink is called. RETURN VALUES
On a successful call, a value of 0 (zero) is returned. Otherwise, a value of -1 is returned and errno is set to indicate that an error occurred. ERRORS
The sem_unlink function fails under the following conditions: [EACCES] Permission is denied to unlink the named semaphore. [ENAMETOOLONG] The length of the name string exceeds {NAME_MAX} while {_POSIX_NO_TRUNC} is in effect. [ENOENT] The named semaphore does not exist. RELATED INFORMATION
Functions: sem_close(3), sem_open(3) Guide to Realtime Programming delim off sem_unlink(3)

Check Out this Related Man Page

SEM_UNLINK(3)						     Linux Programmer's Manual						     SEM_UNLINK(3)

sem_unlink - remove a named semaphore SYNOPSIS
#include <semaphore.h> int sem_unlink(const char *name); Link with -pthread. DESCRIPTION
sem_unlink() removes the named semaphore referred to by name. The semaphore name is removed immediately. The semaphore is destroyed once all other processes that have the semaphore open close it. RETURN VALUE
On success sem_unlink() returns 0; on error, -1 is returned, with errno set to indicate the error. ERRORS
EACCES The caller does not have permission to unlink this semaphore. ENAMETOOLONG name was too long. ENOENT There is no semaphore with the given name. CONFORMING TO
sem_getvalue(3), sem_open(3), sem_post(3), sem_wait(3), sem_overview(7) COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at Linux 2012-05-13 SEM_UNLINK(3)

12 More Discussions You Might Find Interesting

1. Programming

change semaphore perm

Hi, I've a problem with this simple code about of semaphore: #include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<semaphore.h> #include<sys/types.h> #include<sys/mman.h> #include<sys/fcntl.h> #define SemName "/SEM_1" int main (int argc, char **argv) { char name;... (5 Replies)
Discussion started by: FastMagister
5 Replies

2. Programming

semaphore limits

Hi Could anybody tell me how can i see the semaphore limits on my system. I am using solaris 8. Thanks in advance (2 Replies)
Discussion started by: axes
2 Replies

3. UNIX for Dummies Questions & Answers

what is diff b/w semaphore and mutex

can u tell me what is the exact difference b/w mutex and semaphore and what is the diff b/w counting semaphore and binary semaphore amit (1 Reply)
Discussion started by: amitpansuria
1 Replies

4. UNIX for Advanced & Expert Users

semaphore concept

Hi All, I am going through the semaphore concept and have a doubt regarding the same and hope to get a resolution here. I have a file which has a number of records. I want to write an application (in C) which will be able to do concurrent read/write on these records. Of what I have... (8 Replies)
Discussion started by: maverix
8 Replies

5. AIX

how to clean Unused semaphore??

How can i clean up my unused semaphore??? (4 Replies)
Discussion started by: abhishek27
4 Replies

6. Programming

List of suspended tasks on a semaphore/message queue

Hi, I have created a posix semaphore. Is it possible to have a functionality, wherein I can reset the semaphore. ie All the tasks waiting for the semaphore will be signalled and will return with error values and the semaphore value will be set to its initial value. Is there a way to get a... (1 Reply)
Discussion started by: taklubaba
1 Replies

7. UNIX for Dummies Questions & Answers

Determining which processes hold a semaphore

I have a situation where I have created a semaphore and set it's value to 10. I am using this semaphore to control access to a shared memory location. I can have 10 processes simultaneously read from the shared memory location, process 11 would get locked out. My question is, is there a way I... (6 Replies)
Discussion started by: tpotter01
6 Replies

8. UNIX for Dummies Questions & Answers


what is semaphore? can any body explain it in a more simple way than the manual ?? replies appreciated Regards raguram R (7 Replies)
Discussion started by: raguramtgr
7 Replies

9. UNIX for Dummies Questions & Answers

What is the components of semaphore?

What is the components of semaphore? (1 Reply)
Discussion started by: dearanik
1 Replies

10. UNIX for Dummies Questions & Answers

semaphore removal

I have one process which creates semaphore with permission 600. Then at some part of the code I have line where this semaphore will be removed. Problem I have is that other processes in my program also try to execute this line of code. Of course since they dont have permission they wont be able to... (1 Reply)
Discussion started by: joker40
1 Replies

11. Shell Programming and Scripting


Can Someone help me what does the following error mean? ERR: 17-Oct-11 15:07:44: File etlDataLoad.c Line 1069: 895, A fatal error has occured. Posting semaphore information ERR: 17-Oct-11 15:07:44: File etlDataLoad.c Line 1174: 899, Local load partition 0 exited with a failure status of 256... (1 Reply)
Discussion started by: bobby1015
1 Replies

12. Programming

How to implement a semaphore with pedestrian pushbutton

Hello, I need to implement a semaphore in linux c with the following conditions: 1. When there is no pedestrian crossing the street cars can move freely,but if there are any pedestrians crossing the street, the cars have to wait for pedestrians to pass there. 2. Pedestrians have to... (1 Reply)
Discussion started by: NewBe
1 Replies

Featured Tech Videos