day22作业

创建3个子进程，子进程1拷贝文件的前一半，子进程2拷贝文件的后一半，父进程回收两个子进程资源

#include <myhead.h>
int main(int argc, const char *argv[])
{
pid_t pid,pid2;
pid=fork();
if(pid==0)
{
printf("我是子进程1,我拷贝文件前一半\n");
int fd=open("./1.txt",O_RDONLY);
int fd2=open("./2.txt",O_CREAT|O_WRONLY|O_APPEND,0664);
int len=lseek(fd,0,SEEK_END);//文件长度
int mlen=len/2;
lseek(fd,0,SEEK_SET);
char ch[5];
int sum=0;
int yu=mlen%sizeof(ch);
printf("yu=%d\n",yu);

while(1)
{
//ssize_t rdlen=read(fd,ch,len/2);
ssize_t rdlen=read(fd,ch,sizeof(ch));

ssize_t wlen=write(fd2,ch,rdlen);
sum+=rdlen;

if(sum+2==mlen)
{
printf("退出了\n");
break;
}
}
close(fd);
close(fd2);

}
else if(pid>0)
{
printf("我是父进程啊\n");
pid2=fork();
if(pid2>0)
{
printf("我还是父进程啊\n");
while(waitpid(0,NULL,0)!=-1)
{
waitpid(0,NULL,0);
}
}
else if(pid2==0)
{
printf("我是子进程2，我拷贝文件后一半\n");
sleep(10);
int fd=open("./1.txt",O_RDONLY);
int fd2=open("./2.txt",O_CREAT|O_WRONLY|O_APPEND,0664);
int len=lseek(fd,0,SEEK_END);//文件长度
int mlen=len-len/2;
int a=lseek(fd,len/2,SEEK_SET);
lseek(fd2,len/2,SEEK_SET);
char ch[5];
int sum=0;
int yu=mlen%sizeof(ch);
while(1)
{
ssize_t rlen=read(fd,ch,sizeof(ch));
ssize_t wlen=write(fd2,ch,rlen);
sum+=rlen;
if(sum+yu==mlen)
{
printf("读完了\n");
break;
}

}
close(fd);
close(fd2);


}

}
return 0;
}

原文地址：https://blog.csdn.net/sinat_28344841/article/details/143695410

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