1-20-longest-line-extern.c

#include <stdio.h>

#define MAXLINE 1000

int max;
char line[MAXLINE];
char longest[MAXLINE];

int getLine(void);
void copy(void);

int main()
{
  int len;
  extern int max;
  extern char longest[];

  max = 0;
  while ((len = getLine()) > 0)
    if (len > max) {
      max = len;
      copy();
    }

  if (max > 0)
    printf("%s", longest);

  return 0;
}

int getLine(void)
{
  int c, i;
  extern char line[];

  for (i = 0; i < MAXLINE - 1
      && (c = getchar()) != EOF && c!= '\n'; i++)
    line[i] = c;

  if (c == '\n') {
    line[i] = c;
    i++;
  }

  line[i] = '\0';

  return i;
}

void copy(void)
{
  int i;
  extern char line[], longest[];

  i = 0;
  while((longest[i] = line[i]) != '\0')
    i++;
}