c - print longest input line.(example in K&R(2e)(section 1.9)) -

when executing program (in ubuntu) , enter input ($ represents eof(ctrl+d)) :-

giujb   bjb $$ 

it not work
input

giujb        bjb $$$ 

it works.

i think should require give eof twice (in program). can explain why requires give eof 3 times?

my code

#include<stdio.h> #define maxlength 1000 char line[maxlength]; char longest[maxlength]; int getlength(); void copy(); int main() { int max=0,leng=0; while((leng=getlength())>0) { if(leng>max)   {max=leng;   copy();   }  }   if(max>0)  printf("\n%s",longest);  return 0;  }   int getlength()  { char ch;     int i;     for(i=0;(i<(maxlength-1)) && ((ch=getchar())!= eof) && (ch!='\n');++i)     {line[i]=ch;      printf("%d",i);      }      if(ch=='\n')     {line[i]=ch;      ++i;      }     line[i]='\0';     printf("bye");     return i;     }     void copy()     {     int i=0;     while((longest[i]=line[i])!='\0')     ++i;     } 

on linux, ctrl-d not mean end-of-file (eof). means 'end-of-transmission', means typed input sent program. similar newline exception ctrl-d not sent. getchar returns eof when receives empty "transmission". why have type ctrl-d 3 times (or newline followed 2 ctrl-d) 2 eofs.