pthread_key_create(3P)pthread_key_create(3P)NAMEpthread_key_create - thread-specific data key creation
C SYNOPSIS
#include <pthread.h>
int pthread_key_create(pthread_key_t *key, void (*destructor)(void *));
DESCRIPTION
The pthread_key_create() function creates a key that can be used by all
threads in the process to get and set thread-specific data. The newly
created key is returned in the memory pointed to by key.
After a new key is created, all active threads have the value NULL
associated with that key. After a new thread is created, the value NULL
is associated with all keys for that thread.
An optional destructor function may be associated with each key. Upon
thread exit [see pthread_exit()], if a key has a non-NULL destructor
pointer and has a non-NULL value associated with that key, then the
destructor function will be called with the associated value. The order
of destructor calls is unspecified.
If, after the destructor functions have been called for all non-NULL key
values with associated destructor functions, there are still some non-
NULL key values with associated destructor functions, then the process
will be repeated. This loop will continue until no non-NULL key values
with associated destructor functions exist.
DIAGNOSTICS
On success, pthread_key_create() returns zero; otherwise, an error number
is returned:
[EAGAIN] The limit on the total number of keys per process has been
exceeded [see NOTES].
SEE ALSOpthread_setspecific(3P), pthread_getspecific(3P), pthread_key_delete(3P),
pthread_exit(3P), sysconf(3C).
NOTES
The key limit can be obtained from sysconf() using the THREAD_KEYS_MAX
option.
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