NAME

pthread_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 typically 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 number will be returned to indicate the error.

ERRORS

No errors are defined for either function.

SEE ALSO

pthread_key_create(3)

STANDARDS

These functions conform to IEEE Std 1003.1-2001 (“POSIX.1”).