深入Pthread(四)：一次初始化-pthread_once_t用到的API：pthread_once_t once_control = PTHREAD_ONCE_INIT;
int pthread_once(pthread_once_t* once_control, void (*init_routine)(void));
有些事需要一次且仅需要一次执行。通常当初始化应用程序时，可以比较容易地将其放在main函数中。但当你写一个库时，就不能在main里面初始化了，你可以用静态初始化，但使用一次初始化（pthread_once_t）会比较容易些。
例程：#include <pthread.h>
#include "errors.h"
pthread_once_t once_block = PTHREAD_ONCE_INIT;
pthread_mutex_t mutex;
/*This is the one-time initialization routine. It will be
* called exactly once, no matter how many calls to pthread_once
* with the same control structure are made during the course of
* the program.
*/
void once init routine (void)
{
int status; status = pthread_mutex_init (&mutex, NULL); if (status != 0) err_abort (status, "Init Mutex"); }
/* Thread start routine that calls pthread_once.
*/ void *thread routine (void *arg)
{ int status;
status = pthread_once (&once_block, once_init_routine); if (status != 0) err_abort (status, "Once init"); status = pthread_mutex_lock (&mutex); if (status != 0) err_abort (status, "Lock mutex"); printf ("thread routine has locked the mutex./n"); status = pthread_mutex_unlock (&mutex);
if (status ! = 0) err_abort (status, "Unlock mutex"); return NULL; }
int main (int argc, char *argv[])
{ pthread_t thread_id;
char *input, buffer[64]; int status; status = pthread_create (&thread_id, NULL, thread_routine, NULL); if (status != 0) err_abort (status, "Create thread"); status = pthread_once (&once_block, once_init_routine); if (status != 0) err_abort (status, "Once init"); status = pthread_mutex_lock (&mutex); if (status != 0) err_abort (status, "Lock mutex"); printf ("Main has locked the mutex./n"); status = pthread_mutex_unlock (&mutex); if (status != 0) err_abort (status, "Unlock mutex"); status = pthread_join (thread_id, NULL); if (status != 0) err_abort (status, "Join thread"); return 0; }
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