文件I/O操作編程

通過一個簡單的程序完成文件的複製操作，瞭解基本的文件I/O文件讀寫的基本步驟：

#include<stdio.h>
#include<sys/stat.h>
#include<sys/types.h>
#include<fcntl.h>
#include<unistd.h>

#define max 128

int main(){
 int f1,f2;
 char buf[max];
 int readno,writeno;
 char *p = buf;

 if((f1 = open("a.c",O_RDONLY))==-1){
  printf("open f1 failed!");
  return -1;
 }
 if((f2 = open("b.c",O_WRONLY | O_CREAT | O_APPEND,0644))==-1){
  printf("open f2 failed!");
  return -1;
 }

 while((readno = read(f1,buf,max))<=0){
  if(readno == 0){
   printf("successful!");
   break;
  }
  else{
   printf("read failed!");
   return -1;
  }
 }
 while(1){
  if(readno != 0){
   writeno = write(f2,p,readno);
   readno -=writeno;
   if(readno != 0)
    p +=writeno;
  }
  else break;
 }
 close(f1);
 close(f2);
 return 0;
}