程序代码：

#include<stdio.h>
#include<stdlib.h>
int main(void)
{
    char filename[20]={'\0'},buff;
    int line=1;
    FILE *fp;
    puts("please input the file directory");
    scanf("%s",filename);
    if(fp=fopen(filename,"r")==NULL)
        {printf("cannot open the file!\n");
         exit (0);
        }
    printf("open file OK \n%d",line);
     buff=fgetc(fp);
     while(buff !=EOF)
     {    printf("while is OK");
         if(buff=='\n') 
         {line++;
          printf("\n%d",line);
         }
         else putchar(buff);
         buff=fgetc(fp);
     }
     fclose(fp);
     return 0;
}