fork函数

例1：

#include <stdio.h>
#include <unistd.h>

int global_var = 1;

int main(int argc, char* argv[])
{
	int var = 10;

	if(fork() == 0)
	{
		printf("child process global_var = %d var = %d\n", ++global_var, ++var);
	}
	printf("pid = %d global_var = %d var = %d\n", getpid(), global_var, var);

	return 0;
}

输出：

pid = 12681 global_var = 1 var = 10
child process global_var = 2 var = 11
pid = 12682 global_var = 2 var = 11

例2：

#include <stdio.h>
#include <unistd.h>

int global_var = 1;

int main(int argc, char* argv[])
{
	int var = 10;

	if(fork() == 0)
	{
		printf("child process global_var = %d var = %d\n", ++global_var, ++var);
	} else {
		printf("pid = %d global_var = %d var = %d\n", getpid(), global_var, var);
	}

	return 0;
}

输出：

pid = 12870 global_var = 1 var = 10
child process global_var = 2 var = 11

 

例3：

#include <stdio.h>
#include <unistd.h> 

int global_var = 1; 

int main(int argc, char* argv[])
{
    int var = 10; 

    if(fork() == 0)
    {
        printf("child process global_var = %d var = %d\n", ++global_var, ++var);
        exit(0);
        //return 0;
    }
    printf("pid = %d global_var = %d var = %d\n", getpid(), global_var, var); 

    return 0;
}

输出：

pid = 12920 global_var = 1 var = 10
child process global_var = 2 var = 11