【IO进程线程day5作业】

1.

#include 
#include 
#include 
#include 
#include 
int main(int argc, const char *argv[])
{
	pid_t cpid=fork();
	if(cpid>0)
	{
		//父进程
		int fd=open("./1.png",O_RDONLY);
		if(fd<0)
		{
			printf("----\n");
			perror("open");
			return -1;
		}
		off_t all =lseek(fd,0,SEEK_END);
		int len=all/2;
		int fi=open("./copy.txt",O_WRONLY|O_CREAT|O_TRUNC,0777);
		if(fi<0)
		{
			perror("open");
			return -1;
		}
		if(lseek(fi,0,SEEK_END)=len)
		{
			lseek(fd,len,SEEK_SET);			
			char buf[30]="";
			ssize_t res=0;
			while(1)
			{
				res=read(fd,buf,sizeof(buf));
				if(res==0)
				{
					break;
				}
				write(fi,buf,res);
			}


		}

		close(fi);
		close(fd);
		
	}else
	{
		perror("fork");
		return -1;
	}
	while(1)
		sleep(1);
	return 0;
}

2.

结论：子进程不会变成僵尸进程

3.

孤儿进程：

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
int main(int argc, const char *argv[])
{
 
	pid_t cpid=fork();
	if(cpid>0)
	{
		sleep(1);
		printf("cpid=%d\n",cpid);
		exit(0);
 
	}else if(cpid==0)
	{
		sleep(3);
		while(1)
		{
			sleep(1);
			printf("hello\t  %d\n",getpid());
		}
	}
	else
	{
		perror("fork");
		return -1;
	}
 
	while(1)
		sleep(1);
	return 0;
}

僵尸进程：

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
int main(int argc, const char *argv[])
{
	pid_t cpid=fork();
	if(cpid>0)
	{
		sleep(3);

	}else if(cpid==0)
	{
		sleep(1);
		exit(0);
	}
	else
	{
		perror("fork");
		return -1;
	}

	while(1)
		sleep(1);
	return 0;
}