文件操作

#include <stdio.h>
#include <stdlib.h>

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

#define MAX 100

int read_line(int fd, char *buf, int count)
{
 int i;
 char ch;

 for(i = 0; i < count; i++)
 {
        if((read(fd,&ch,1)) < 0)
  {
   perror("read error!\n");
   exit(1);
  }

  if(ch == '\n')
  {
             buf[i] = '\0';
    return i;
  }

  buf[i] = ch;
 }

 buf[i - 1] = '\0';
 
 return count;
}

int main()
{
 int i;
 int fd;
 int w_count;
 int r_count;
 char filename[MAX];

 char r_buf[MAX];
 char w_buf[MAX];

 printf("Please input filename:\n");
 scanf("%s",filename);

 if((fd = open(filename, O_CREAT | O_RDWR, 0755)) < 0)
 {
  perror("open error!\n");
  exit(1);
 }

 
    for(i = 0; i < 3; i++)
 {
        memset(w_buf,0,sizeof(w_buf));
  scanf("%s",w_buf);
  
  if((w_count = write(fd,w_buf,strlen(w_buf))) < 0)
  {
   perror("write error!\n");
   exit(1);
  }
  else
  {
   write(fd,"\n",1);
  }
 }
   
    lseek(fd,0,SEEK_SET);
#if 0
 if((r_count = read(fd,r_buf,sizeof(r_buf))) < 0)
 {
  perror("read error!\n");
  exit(1);
 }
 else
 {
  r_buf[w_count * 3 + 3] = '\0';
  printf("read data: %s\n",r_buf);
 }
#endif

 for(i = 0; i < 3; i++)
 {
        memset(r_buf,0,sizeof(r_buf));
  read_line(fd,r_buf,100);
  printf("read data: %s\n",r_buf);
 }

 close(fd);

 return 0;
}