创建两个文件，并将文件中对应的数字相加

手动创建两个文本文件text1.txt,text2.txt,要求编程创建text3.txt,实现text1.txt和text2.txt文件中除去首行和末尾，其余对应的数据相加,三个文本的内容如下

text1.txt
begin
10 11 12
20 21 22
30 31 32
end

text2.txt
begin
15 16 17
25 26 27
35 36 37
end

text3.txt
begin
25 27 29
45 47 49
65 67 69
end
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#define BUFFERSIZE 1024

int main()
{
int fd1;
int fd2;
int fd3;
int len1;
int len2;
int i;
int read_bytes;
int write_bytes;

char buffer1[BUFFERSIZE];
char buffer2[BUFFERSIZE];
char buffer3[BUFFERSIZE];
char *ptr;

fd1 = open("text1.txt", O_RDONLY);
fd2 = open("text2.txt", O_RDONLY);
fd3 = open("text3.txt", O_WRONLY | O_CREAT, S_IRUSR | S_IWUSR);

len1 = read(fd1, buffer1, BUFFERSIZE);
len2 = read(fd2, buffer2, BUFFERSIZE);
while(read_bytes = read(fd1, buffer1, BUFFERSIZE))
{
if(-1 == read_bytes)
{
break;
}
}
buffer1[len1] = '\0';
while(read_bytes = read(fd2, buffer2, BUFFERSIZE))
{
if(-1 == read_bytes)
{
break;
}
}
buffer2[len2] = '\0';

strcpy(buffer3, buffer2);
i = 0;
while(buffer2[i] != '\0')
{
if((buffer2[i] >= '0') && (buffer2[i] <= '9'))
{
buffer3[i] = buffer1[i] + buffer2[i] - '0';
}
i++;
}

write(fd3, buffer3, strlen(buffer1));
printf("%s\n", buffer3);
close(fd1);
close(fd2);
close(fd3);

return 0;
}