longest-line.c

#include <stdio.h>
// maximum length of input line
#define MAX_LINE_LENGTH 100

// reads character and puts in line[] and returns its length
int get_line(char line[]) {
  int c, i;
  // add character to line string if its valid
  for (i = 0; i < MAX_LINE_LENGTH - 1 && (c = getchar()) != '\n' && c != EOF;
       i++)
    line[i] = c;
  // add new line encountered at the end of the line
  if (c == '\n') {
    line[i] = c;
    i++;
  }
  // put null character at the end of line to make it valid string
  line[i] = '\0';

  return i;
}

// copy string (or array) of characters
void copy(char *from, char *to) {
  while ((*to++ = *from++))
    ;
}
int main() {
  char current_line[MAX_LINE_LENGTH];
  char longest_line[MAX_LINE_LENGTH];
  int longest_length = 0;
  int current_line_length;

  while ((current_line_length = get_line(current_line)) > 0) {
    if (current_line_length > longest_length) {
      longest_length = current_line_length;
      copy(current_line, longest_line);
    }
  }

  // print if any valid longest line is found
  if (longest_length > 0) {
    printf("longest line is given below:\n");
    printf("%s", longest_line);
  } else
    printf("no longest line found");
  return 0;
}