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I was asked to add this piece of code to a c program which I will execute through the shell:
for(long i = 0; i < NITER; i++)
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Can anyone tell me abt the Semaphore concept and what is semaphore???
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what is semaphore? can any body explain it in a more simple way than the manual ??
replies appreciated
Regards
raguram R (7 Replies)
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Hi,
I am looking to use a semaphore for the first time in one of my scripts. I am just wondering if there are any simple examples or tutorials around?
I am a beginner so the simpler the better :)
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Hi All,
I am going through the semaphore concept and have a doubt regarding the same and hope to get a resolution here.
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I'm running one multithreaded application, in that one of my thread
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Hi,
I'm new to UNIX.
I need to know what's a semaphore
Do reply.
Thanks
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hi, is there any command where we can monitor semaphores? (1 Reply)
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SEM_INIT(3) Linux Programmer's Manual SEM_INIT(3)
NAME
sem_init - initialize an unnamed semaphore
SYNOPSIS
#include <semaphore.h>
int sem_init(sem_t *sem, int pshared, unsigned int value);
Link with -lrt or -pthread.
DESCRIPTION
sem_init() initializes the unnamed semaphore at the address pointed to by sem. The value argument specifies the initial value for the sem-
aphore.
The pshared argument indicates whether this semaphore is to be shared between the threads of a process, or between processes.
If 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).
If pshared is nonzero, then the semaphore is shared between processes, and should be located in a region of shared memory (see shm_open(3),
mmap(2), and shmget(2)). (Since a child created by 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 sem_post(3), sem_wait(3), etc.
Initializing a semaphore that has already been initialized results in undefined behavior.
RETURN VALUE
sem_init() returns 0 on success; on error, -1 is returned, and errno is set to indicate the error.
ERRORS
EINVAL value exceeds SEM_VALUE_MAX.
ENOSYS pshared is nonzero, but the system does not support process-shared semaphores (see sem_overview(7)).
CONFORMING TO
POSIX.1-2001.
NOTES
Bizarrely, POSIX.1-2001 does not specify the value that should be returned by a successful call to sem_init(). POSIX.1-2008 rectifies
this, specifying the zero return on success.
SEE ALSO
sem_destroy(3), sem_post(3), sem_wait(3), sem_overview(7)
COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2008-07-27 SEM_INIT(3)