pthread_getspecific(3T)

NAME

pthread_getspecific(), pthread_setspecific() — get or set the thread-specific data associated with a key

SYNOPSIS

#include <pthread.h>

void *pthread_getspecific( 
   pthread_key_t key 
); 

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

PARAMETERS

key: Thread-specific data key whose value for the calling thread is to be set or retrieved.
value: Value to be assigned to the thread-specific data key for the calling thread.

DESCRIPTION

The pthread_getspecific() function returns the thread-specific data value associated with key for the calling thread. If no value has been associated with key for the calling thread, NULL is returned.

The pthread_setspecific() function associates the thread-specific data value with key. Each thread may bind a different value to key. These values are usually pointers to memory dynamically allocated by the calling thread.

key must be a valid thread-specific data key created by calling pthread_key_create(). If key is not a valid thread-specific data key, undefined behavior results when calling these functions.

These functions may be called from a thread-specific data destructor function. However, calling pthread_setspecific() from a destructor may result in lost storage.

RETURN VALUE

The function pthread_getspecific() returns the thread-specific data value associated with key. If no thread-specific data value is currently associated with key, the value NULL is returned.

If successful, pthread_setspecific() returns zero. Otherwise, an error number is returned to indicate the error (the errno variable is not set).

ERRORS

No errors are returned by the pthread_getspecific() function.

If any of the following occur, the pthread_setspecific() function returns the corresponding error number:

[ENOMEM]: There is insufficient memory available in which to associate value with key.

For each of the following conditions, if the condition is detected, the pthread_setspecific() function returns the corresponding error number:

[EINVAL]: key is an invalid thread-specific data key.

AUTHOR

pthread_getspecific() and pthread_setspecific() were derived from the IEEE POSIX P1003.1c standard.

STANDARDS CONFORMANCE

pthread_getspecific(): POSIX 1003.1c.
pthread_setspecific(): POSIX 1003.1c.

pthread_getspecific(3T)

Technical documentation

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