C语言中pthread_create函数实现向线程函数传递参数
作者:焱齿
本文主要介绍了C语言中pthread_create函数实现向线程函数传递参数,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友们下面随着小编来一起学习学习吧
一、pthread_create函数:
1、简介:pthread_create是UNIX环境创建线程的函数
2、头文件:#include <pthread.h>
3、函数声明:
int pthread_create(pthread_t* restrict tidp,const pthread_attr_t* restrict_attr,void* (*start_rtn)(void*),void *restrict arg);
4、输入参数:(以下做简介,具体参见实例一目了然)
(1)tidp:事先创建好的pthread_t类型的参数。成功时tidp指向的内存单元被设置为新创建线程的线程ID。
(2)attr:用于定制各种不同的线程属性。APUE的12.3节讨论了线程属性。通常直接设为NULL。
(3)start_rtn:新创建线程从此函数开始运行。无参数是arg设为NULL即可。
(4)arg:start_rtn函数的参数。无参数时设为NULL即可。有参数时输入参数的地址。当多于一个参数时应当使用结构体传入。(以下举例)
5、返回值:成功返回0,否则返回错误码。
6、说明。
传递参数的时候传地址: pthread_create(&ntid, NULL, thr_fn, ¶m1);
线程函数的第一句通常是获取传入参数:Param tmp = *(Param *)arg;
举例如下:
二、不向线程函数传递参数:
#include "apue.h" #include <pthread.h> #include "apueerror.h" #include <iostream> #include <string> using namespace std; pthread_t ntid; void printids(const char *s){ pid_t pid; pthread_t tid; pid = getpid(); tid = pthread_self(); printf("%s pid %lu tid %lu (0x%lx)\n", s, (unsigned long)pid, (unsigned long)tid, (unsigned long)tid); } void *thr_fn(void *arg){ cout << "----enter sub thread--------" << endl; printids("new thread: "); cout << "Change to C++ code!!" << endl; cout << "----exit from sub thread----" << endl; return((void *)0); } int main(void){ int err; //第四个参数为NULL,说明没有向线程函数传参数。 err = pthread_create(&ntid, NULL, thr_fn, NULL); if (err != 0) err_exit(err, "can't create thread"); printids("main thread:"); sleep(1); exit(0); }
三、向线程函数传递一个参数:
#include "apue.h" #include <pthread.h> #include "apueerror.h" #include <iostream> #include <string> using namespace std; pthread_t ntid; void printids(const char *s){ pid_t pid; pthread_t tid; pid = getpid(); tid = pthread_self(); printf("%s pid %lu tid %lu (0x%lx)\n", s, (unsigned long)pid, (unsigned long)tid, (unsigned long)tid); } struct Param { int a; int b; int c; }; void *thr_fn( void *arg ) { cout << "----enter sub thread--------" << endl; int tmp = *(int *)arg; cout << "tmp=" << tmp << endl; printids("new thread: "); cout << "Change to C++ code!!" << endl; cout << "----exit from sub thread----" << endl; return((void *)0); } int main(void){ int err; int num = 123; //向线程函数传入一个参数。 err = pthread_create(&ntid, NULL, thr_fn, &num); if (err != 0) err_exit(err, "can't create thread"); printids("main thread:"); sleep(1); exit(0); }
四、向线程函数传递两个或以上的参数:
#include "apue.h" #include <pthread.h> #include "apueerror.h" #include <iostream> #include <string> using namespace std; pthread_t ntid; void printids(const char *s){ pid_t pid; pthread_t tid; pid = getpid(); tid = pthread_self(); printf("%s pid %lu tid %lu (0x%lx)\n", s, (unsigned long)pid, (unsigned long)tid, (unsigned long)tid); } struct Param { int a; int b; int c; }; void *thr_fn(void *arg) { cout << "----enter sub thread--------" << endl; Param tmp = *(Param *)arg; cout << "tmp.a=" << tmp.a << endl; cout << "tmp.b=" << tmp.b << endl; cout << "tmp.c=" << tmp.c << endl; printids("new thread: "); cout << "Change to C++ code!!" << endl; cout << "----exit from sub thread----" << endl; return((void *)0); } int main(void){ int err; int num = 123; Param param1; param1.a = 11; param1.b = 22; param1.c = 33; //通过结构体向线程函数传入多个参数 err = pthread_create(&ntid, NULL, thr_fn, ¶m1); if (err != 0) err_exit(err, "can't create thread"); printids("main thread:"); sleep(1); exit(0); }
执行效果如下:
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