UNIX环境高级编程第11章线程

 

 

 

 

 

 

 

程序清单11-1打印线程ID

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// threads/threadid.c 11-1 #include "apue.h" #include <pthread.h>   pthread_t ntid;   void printids(const char* s) {     printf("%d ", (unsigned int)ntid);     printf("%ld ", (unsigned long)ntid);     pid_t     pid;     pthread_t tid;       pid = getpid();     tid = pthread_self();     // printf("%s pid %u tid %u (0x%x)\n", s, (unsigned int)pid, (unsigned int)tid, (unsigned int)tid);     printf("%s pid %lu tid %lu (0x%lx)\n", s, (unsigned long)pid, (unsigned long)tid, (unsigned long)tid); }   void* thr_fn(void* arg) {     printids("new thread: ");     return((void *)0); }   /*This example has two oddities, which are necessary to handle races between the main  * thread and the new thread. (We'll learn better ways to deal with these conditions later  * in this chapter.) The first is the need to sleep in the main thread. If it doesn't sleep, the  * main thread might exit, thereby terminating the entire process before the new thread  * gets a chance to run. This behavior is dependent on the operating system's threads  * implementation and scheduling algorithms.  * The second oddity is that the new thread obtains its thread ID by calling  * pthread_self instead of reading it out of shared memory or receiving it as an  * argument to its thread-start routine. Recall that pthread_create will return the  * thread ID of the newly created thread through the first parameter (tidp). In our  * example, the main thread stores this ID in ntid, but the new thread can¡¯t safely use it.  * If the new thread runs before the main thread returns from calling pthread_create,  * then the new thread will see the uninitialized contents of ntid instead of the thread ID.  */ int main(void) {     int err;       err = pthread_create(&ntid, NULL, thr_fn, NULL);     if (0 != err)         err_quit("can't create thread: %s\n", strerror(err));     printids("main thread:");     sleep(1);     return 0; }

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all: threadid threadid: threadid.c     g++ -g -Wall threadid.c ../lib/libapue.a -I ../include -lpthread -o threadid clean:     rm threadid

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这和我在虚拟机centos6.3中测试的情况不同，centos下进程ID是相同的（3607），并不是不同的。