1，思维导图

2，使用read和write实现文件拷贝

#include<myhead.h>
int main(int argc, const char *argv[])
{
	int fp1,fp2;
	char a[1];
	fp1=open("./1.txt",O_RDONLY);
	fp2=open("./2.txt",O_CREAT|O_TRUNC|O_WRONLY,0664);
	if(fp1==-1||fp2==-1)
	{
		perror("open");
		return -1;
	}
    int c;
	while(c=read(fp1,a,sizeof(a)))
	{
		if(write(fp2,a,sizeof(a))!=c)
          {
              break;
          }
	}
	close(fp1);
	close(fp2);
	fp2=open("./2.txt",O_RDONLY);
	if(fp2==-1)
	{
		perror("open");
		return -1;
	}
    char n;
	while(read(fp2,&n,sizeof(a))
	{
		printf("%c",n);
	}
	close(fp2);
	return 0;
}