HP-UX Reference (11i v2 04/09) - 3 Library Functions N-Z (vol 7)

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pthread_cond_init(3T) pthread_cond_init(3T)
(Pthread Library)
NAME
pthread_cond_init(), pthread_cond_destroy() - initialize or destroy a condition variable.
SYNOPSIS
#include <pthread.h>
int pthread_cond_init(
pthread_cond_t *cond,
const pthread_condattr_t *attr
);
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
int pthread_cond_destroy(
pthread_cond_t *cond
);
PARAMETERS
cond Pointer to the condition variable to be initialized or destroyed.
attr Pointer to the attributes object that defines the characteristics of the condition variable to
be initialized. If the pointer is
NULL
, default attributes are used.
DESCRIPTION
The
pthread_cond_init()
function initializes the condition variable cond with the attributes attr.
If attr is
NULL, the default condition variable attributes are used to initialize the attributes object. Refer
to pthread_condattr_init()
for a list of the default condition variable attributes. After successful
initialization, the condition variable may be used in condition variable operations. A condition variable
should be initialized only once or the resulting behavior is undefined. The
pthread_once()
function
provides a way to ensure that a condition variable is only initialized once.
The macro
PTHREAD_COND_INITIALIZER
can be used to initialize condition variables that are stati-
cally allocated. These condition variables will be initialized with default attributes. The
pthread_cond_init()
function does not need to be called for statically initialized condition vari-
ables.
If the process-shared attribute in the condition variable attributes object referenced by attr is defined as
PTHREAD_PROCESS_SHARED
, the condition variable must be allocated such that the processes sharing
the condition variable have access to it. This may be done through the memory-mapping functions (see
mmap(2)) or the shared memory functions (see shmget(2)).
pthread_cond_destroy()
destroys the condition variable cond. This function may set cond to an
invalid value. The destroyed condition variable can be reinitialized using the function
pthread_cond_init()
. If the condition variable is used after destruction in any condition variable
call, the resulting behavior is undefined.
A condition variable should be destroyed only when there are no threads currently blocked on it. Des-
troying a condition variable that is currently in use results in undefined behavior.
RETURN VALUE
Upon successful completion,
pthread_cond_init() and pthread_cond_destroy()
return zero.
Otherwise, an error number is returned to indicate the error (the
errno variable is not set).
ERRORS
If any of the following occur, the
pthread_cond_init() function returns the corresponding error
number:
[EAGAIN] The system does not have the available resources (other than memory) to initialize
the condition variable.
[ENOMEM] There is insufficient memory available in which to initialize the condition variable.
For each of the following conditions, if the condition is detected, the
pthread_cond_init() function
returns the corresponding error number:
[EINVAL] The value specified by cond or attr is invalid.
[EBUSY] The specified condition variable is an already initialized condition variable.
HP-UX 11i Version 2: September 2004 − 1 − Hewlett-Packard Company Section 3−−767