January 30, 2003 PTHREAD_SETSPECIFIC 3

### NAME

pthread_setspecific - set a thread-specific data value

### LIBRARY

POSIX Thread Library (libpthread, -lpthread)

### SYNOPSIS

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

### DESCRIPTION

The pthread_setspecific(``) function associates a thread-specific value with a ```key` obtained via a previous call to pthread_key_create(``). 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.

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

pthread_setspecific(``) may be called from a thread-specific data destructor function, however this may result in lost storage or infinite loops.

### RETURN VALUES

If successful, the pthread_setspecific(``) function will return zero. Otherwise an error number will be returned to indicate the error.

### ERRORS

pthread_setspecific(``) shall fail if:

[```ENOMEM`]
  Insufficient memory exists to associate the value with the ```key`.

pthread_setspecific(``) may fail if:

[```EINVAL`]
  The ```key` value is invalid.

### SEE ALSO

pthread_getspecific(3), pthread_key_create(3), pthread_key_delete(3)

### STANDARDS

pthread_setspecific(``) conforms to ISO/IEC 9945-1:1996 (``POSIX.1'') .