Linux and UNIX Man Pages

Test Your Knowledge in Computers #64
Difficulty: Easy
HTTP uses UDP as the core transport protocol on the Internet.
True or False?
Linux & Unix Commands - Search Man Pages

sem_init(3c) [opensolaris man page]

sem_init(3C)						   Standard C Library Functions 					      sem_init(3C)

sem_init - initialize an unnamed semaphore SYNOPSIS
#include <semaphore.h> int sem_init(sem_t *sem, int pshared, unsigned int value); DESCRIPTION
The sem_init() function is used to initialize the unnamed semaphore referred to by sem. The value of the initialized semaphore is value. Following a successful call to sem_init(), the semaphore may be used in subsequent calls to sem_wait(3C), sem_trywait(3C), sem_post(3C), and sem_destroy(3C). This semaphore remains usable until the semaphore is destroyed. If the pshared argument has a non-zero value, then the semaphore is shared between processes; in this case, any process that can access the semaphore sem can use sem for performing sem_wait(3C), sem_trywait(3C), sem_post(3C), and sem_destroy(3C) operations. Only sem itself may be used for performing synchronization. The result of referring to copies of sem in calls to sem_wait(3C), sem_try- wait(3C), sem_post(3C), and sem_destroy(3C), is undefined. If the pshared argument is zero, then the semaphore is shared between threads of the process; any thread in this process can use sem for performing sem_wait(3C), sem_trywait(3C), sem_post(3C), and sem_destroy(3C) operations. The use of the semaphore by threads other than those created in the same process is undefined. Attempting to initialize an already initialized semaphore results in undefined behavior. RETURN VALUES
Upon successful completion, the function initializes the semaphore in sem. Otherwise, it returns -1 and sets errno to indicate the error. ERRORS
The sem_init() function will fail if: EINVAL The value argument exceeds SEM_VALUE_MAX. ENOSPC A resource required to initialize the semaphore has been exhausted, or the resources have reached the limit on semaphores (SEM_NSEMS_MAX). ENOSYS The sem_init() function is not supported by the system. EPERM The process lacks the appropriate privileges to initialize the semaphore. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ |ATTRIBUTE TYPE |ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Committed | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ |Standard |See standards(5). | +-----------------------------+-----------------------------+ SEE ALSO
sem_destroy(3C), sem_post(3C), sem_wait(3C), attributes(5), standards(5) SunOS 5.11 5 Feb 2008 sem_init(3C)

Featured Tech Videos