pthread_getspecific

, pthread_setspecific

- manage thread-specific data

Synopsis

cc –mt [ flag... ] file... [ library... ]
#include <pthread.h>

int pthread_setspecific(pthread_key_t key, const void *value);

void *pthread_getspecific(pthread_key_t key);

Description

The pthread_setspecific() function associates a thread-specific value with a key obtained by way of a previous call to pthread_key_create(). Different threads may bind different values to the same key. These values are typically pointers to blocks of dynamically allocated memory that have been reserved for use by the calling thread.

The pthread_getspecific() function returns the value currently bound to the specified key on behalf of the calling thread.

The effect of calling pthread_setspecific() or pthread_getspecific() with a key value not obtained from pthread_key_create() or after key has been deleted with pthread_key_delete() is undefined.

Both pthread_setspecific() and pthread_getspecific() may be called from a thread-specific data destructor function. However, calling pthread_setspecific() from a destructor may result in lost storage or infinite loops.

Return Values

The pthread_getspecific() function returns 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.

Upon successful completion, the pthread_setspecific() function returns 0. Otherwise, an error number is returned to indicate the error.

Errors

The pthread_setspecific() function will fail if:

ENOMEM

Insufficient memory exists to associate the value with the key.

The pthread_setspecific() function may fail if:

EINVAL

The key value is invalid.

The pthread_getspecific() function does not return errors.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

pthread_key_create(3C), attributes(5), standards(5)