标签：函数返回值 waitpid col nis led printf -668 调用 函数
阻塞等待线程退出，获取线程退出状态 其作用，对应进程中 waitpid() 函数。
int pthread_join(pthread_t thread, void **retval); 成功：0；失败：错误号
参数：thread：线程ID （【注意】：不是指针）；retval：存储线程结束状态。
对比记忆：
进程中：main返回值、exit参数-->int；等待子进程结束 wait 函数参数-->int *
线程中：线程主函数返回值、pthread_exit-->void *；等待线程结束 pthread_join 函数参数-->void **
【练习】：参数 retval 非空用法。 【pthrd_exit_join.c】
调用该函数的线程将挂起等待，直到id为thread的线程终止。thread线程以不同的方法终止，通过pthread_join得到的终止状态是不同的，总结如下：
【练习】：使用pthread_join函数将循环创建的多个子线程回收。
/*** thread_join.c ***/ #include<stdio.h> #include<error.h> #include<string.h> #include<unistd.h> #include<stdlib.h> #include<pthread.h> typedef struct { char ch; int var; char str[64]; }exit_t; void *thrd_func(void *arg) { pthread_exit((void *)1); } int main() { pthread_t tid; int ret; int *retval; printf("In main 1 : thread id = %lu, pid = %u\n",pthread_self(),getpid()); ret = pthread_create(&tid,NULL,thrd_func,NULL); if(0 != ret) { fprintf(stderr,"pthread_create error : %s \n",strerror(ret)); exit(1); } pthread_join(tid,(void **)&retval); printf("--------------%d\n",(int)retval); pthread_exit((void*)1); }
运行结果：
ubuntu1604@ubuntu:~/wangqinghe/linux/20190819$ ./thread_join
In main 1 : thread id = 139721544345344, pid = 12974
--------------1
/*** pthread_join_struct.c ***/ #include<stdio.h> #include<error.h> #include<string.h> #include<unistd.h> #include<stdlib.h> #include<pthread.h> typedef struct { char ch; int var; char str[64]; }exit_t; void *thrd_func(void *arg) { exit_t *retvar = (exit_t *)malloc(sizeof(exit_t)); retvar->ch = ‘m‘; retvar->var = 200; strcpy(retvar->str,"my thread\n"); pthread_exit((exit_t *)retvar); } int main() { pthread_t tid; int ret; exit_t *retval; printf("In main 1 : thread id = %lu, pid = %u\n",pthread_self(),getpid()); ret = pthread_create(&tid,NULL,thrd_func,NULL); if(0 != ret) { fprintf(stderr,"pthread_create error : %s \n",strerror(ret)); exit(1); } pthread_join(tid,(void **)&retval); printf("ch = %c,var = %d,str = %s\n--------------%d\n",retval->ch,retval->var,retval->str); free(retval); pthread_exit((void*)1); }
运行结果：
ubuntu1604@ubuntu:~/wangqinghe/linux/20190819$ ./thread_join
In main 1 : thread id = 140316487100160, pid = 13121
ch = m,var = 200,str = my thread
--------------202
/*** thread_join_loop.c ***/ #include<stdio.h> #include<string.h> #include<unistd.h> #include<pthread.h> int var = 100; void *tfn(void *arg) { int i; i = (int)arg; sleep(i); if(1 == i) { var = 333; printf("var = %d\n",var); return (void*)var; } else if( 3 == i) { var = 888; printf("i‘m %dth pthread,pthread id = %lu ,var = %d\n",i+1,pthread_self(),var); pthread_exit((void*)var); } else { printf("i‘m %dth pthread,pthread id = %lu ,var = %d\n",i+1,pthread_self(),var); pthread_exit((void*)var); } return NULL; } int main() { pthread_t tid[5]; int i; int *ret[5]; for(i = 0; i < 5; i++) { pthread_create(&tid[i],NULL,tfn,(void*)i); } for(i = 0; i < 5; i++) { pthread_join(tid[i],(void**)&ret[i]); printf("-----------%d‘s ret = %d\n",(int)ret[i]); } printf("I‘m main pthread tid = %lu var = %d\n",pthread_self(),var); sleep(i); return 0; }
运行结果：
ubuntu1604@ubuntu:~/wangqinghe/linux/20190819$ ./thread_loop
i‘m 1th pthread,pthread id = 139809124009728 ,var = 100
-----------100‘s ret = -645238160
var = 333
-----------333‘s ret = -651408960
i‘m 3th pthread,pthread id = 139809107224320 ,var = 333
-----------333‘s ret = -659801664
i‘m 4th pthread,pthread id = 139809098831616 ,var = 888
-----------888‘s ret = -668194368
i‘m 5th pthread,pthread id = 139809090438912 ,var = 888
-----------888‘s ret = 0
I‘m main pthread tid = 139809132349184 var = 888
标签：函数返回值 waitpid col nis led printf -668 调用 函数
原文地址：https://www.cnblogs.com/wanghao-boke/p/11389714.html
