PTHREAD_GETSPECIFIC(3) BSD Library Functions Manual PTHREAD_GETSPECIFIC(3)NAMEpthread_getspecific — thread-specific data value
LIBRARY
POSIX Threads Library (libpthread, -lpthread)
SYNOPSIS
#include <pthread.h>
void *
pthread_getspecific(pthread_key_t key);
int
pthread_setspecific(pthread_key_t key, const void *value);
DESCRIPTION
The pthread_getspecific() function returns the value currently bound to
the specified key on behalf of the calling thread. Conversely, the
pthread_setspecific() function associates a thread-specific value with a
key obtained via a previous call to pthread_key_create(3). Different
threads have different values bound to each key. These values are typi‐
cally pointers to blocks of dynamically allocated memory that have been
reserved for use by the calling thread.
Undefined behavior may follow if either function is called with a key
value not obtained from pthread_key_create(3), or if the call is made
after key has been deleted with pthread_key_delete(3). It is possible to
call either function from a thread-specific data destructor function.
Note however that this is not well defined for the pthread_setspecific()
function; lost storage or infinite loops may occur.
RETURN VALUES
The pthread_getspecific() function will return the thread-specific data
value associated with the given key. If no thread-specific data value is
associated with key, then the value NULL is returned. If successful, the
pthread_setspecific() function will return zero. Otherwise an error num‐
ber will be returned to indicate the error.
ERRORS
No errors are defined for either function.
SEE ALSOpthread_key_create(3)STANDARDS
These functions conform to IEEE Std 1003.1-2001 (“POSIX.1”).
BSD July 9, 2010 BSD
