练习1-16：修改打印最长文本行的程序的主程序main，使之可以打印任意长度的输入行的长度，并尽可能多地打印文本（C程序设计语言 第2版）

Answer to Exercise 1-16, page 30
Revise the main routine of the longest-line program so it will correctly print the length of arbitrarily long input lines, and as much as possible of the text.

/* This is the first program exercise where the spec isn't entirely
* clear. The spec says, 'Revise the main routine', but the true
* length of an input line can only be determined by modifying
* getline. So that's what we'll do. getline will now return the
* actual length of the line rather than the number of characters
* read into the array passed to it.
*/

#include <stdio.h>

#define MAXLINE 1000 /* maximum input line size */

int getline(char line[], int maxline);
void copy(char to[], char from[]);

/* print longest input line */
int main(void)
{
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)
{
printf("%d: %s", len, line);

if(len > max)
{
max = len;
copy(longest, line);
}
}
if(max > 0)
{
printf("Longest is %d characters:\n%s", max, longest);
}
printf("\n");
return 0;
}

/* getline: read a line into s, return length */
int getline(char s[], int lim)
{
int c, i, j;

for(i = 0, j = 0; (c = getchar())!=EOF && c != '\n'; ++i)
{
if(i < lim - 1)
{
s[j++] = c;
}
}//这里getline修改后，i可以大于lim限制，只计数，不保存字符。
if(c == '\n')
{
if(i <= lim - 1)
{
s[j++] = c;
}
++i;
}
s[j] = '\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;
}
}