linux 多线程基础

参考出处：http://www.cnblogs.com/skynet/archive/2010/10/30/1865267.html

一、进程与线程

    进程是程序代码在系统中的具体实现。进程是拥有所需资源和执行方案的集合。

    线程是进程中划分出的可独立执行的一个控制流程。

    二者区别：

        每一个进程有各自独立的地址空间。进程崩溃不会影响到其余进程。

        全部线程共享同一进程的资源，除了局部变量和堆以外。线程的崩溃会致使所在进程的挂起。

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <errno.h>
#include <unistd.h>

int g_Flag = 0;
 
void* thread1( void* );
void* thread2( void* );

int main( int argc, char* argv[] )
{
    printf(" Enter main\n ");

    pthread_t tid1, tid2;
    int rc1 = 0;
    int rc2 = 0;

    rc2 = pthread_create( &tid2, NULL, thread2, NULL );
    if ( 0 != rc2 )
    {
        printf("%s: %d\n", __func__, strerror(rc2) );
    }

    rc1 = pthread_create( &tid1, NULL, thread1, NULL );
    if ( 0 != rc1 )
    {
        printf( "%s: %d\n", __func__, strerror( rc1 ) );
    }
    printf( "leave main\n" );


    getchar();

    exit( 0 );
}

void* thread1( void* arg )
{    
    printf( "Enter thread1\n" );
    printf( "This is thread1, g_Flag : %d, thread id is %u\n", g_Flag, ( unsigned int )pthread_self()  );
    g_Flag = 1; 
    printf( "This is thread1, g_Flag : %d, thread_id is %u\n", g_Flag, ( unsigned int )pthread_self()  );
    printf( "leave thread\n" );
    pthread_exit( 0 );
}

void* thread2( void* arg )
{
    printf( "Enter thread2\n" );
    printf( "This is thread2, g_Flag : %d, thread_id is %u\n", g_Flag, (unsigned int )pthread_self() );
    g_Flag = 2; 
    printf( "This is thread2, g_Flag :%d, thread_id is %u\n", g_Flag, (unsigned int )pthread_self() );
    pthread_exit( 0 );
}