#include <stdio.h>
   #define MAXLINE 1000   /* maximum input line length */
  int getline(char line[], int maxline);
   void copy(char to[], char from[]);
   /* print the longest input line */
   main()
   {
       int len;            /* current line length */
       int max;            /* maximum length seen so far */
       char line[MAXLINE];    /* current input line */
       char longest[MAXLINE]; /* longest line saved here */
       max = 0;
       while ((len = getline(line, MAXLINE)) > 0)
           if (len > max) {
               max = len;
               copy(longest, line);
           }
       if (max > 0)  /* there was a line */
           printf("%s", longest);
       return 0;
   }
   /* getline:  read a line into s, return length  */
   int getline(char s[],int lim)
   {
       int c, i;
       for (i=0; i < lim-1 && (c=getchar())!=EOF && c!='\n'; ++i)
           s[i] = c;
       if (c == '\n') {
           s[i] = c;
           ++i;
       }
       s[i] = '\0';
       return i;
   }
   /* copy:  copy 'from' into 'to'; assume to is big enough */
   void copy(char to[], char from[])
   {
       int i;
       i = 0;
       while ((to[i] = from[i]) != '\0')
           ++i;
   }
修改main函数，使得该程序可以打印任意长度的行。

就是你输入时可以任意多行，在结束串流的时候依照原样输出，至于为什么用串流呢？主要是考虑c语言编程中许多文件关闭。。。额，你复制我那个程序，这个程序是输出你输入所有行中最长行。我主要是不会改main函数使其可以全部输出输入的所有行？懂了么？亲。。让你们费解，是在抱歉哈