maxline.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int mkdstr(char **, int (*)(void));

int main() {
    int no = 0;
    int len;
    int max_no;
    int max_len = 0;
    char *line, *max;

    max = (char *) malloc(0);
    while (mkdstr(&line, &getchar)) {
        no++;
        len = strlen(line);
        if (len > max_len) {
            max = (char *) realloc(max, len);
            strcpy(max, line);
            max_no = no;
            max_len = len;
        }
    }

    printf("%d %s\n", max_no, max);

    return 0;
}

#define DSTR_INIT 10

int mkdstr(char **res, int (*get)(void)) {
    char c, *r;
    int size = DSTR_INIT;
    int count = 0;

    free(*res);
    *res = (char *) malloc(size);
    r = *res;
    while ((c = (*get)()) != EOF && c != '\n') {
        if (count == size) {
            size *= 2;
            *res = (char *) realloc(*res, size);
            r = *res + count;
        }
        *r++ = c;
        count++;
    }
    *r = '\0';
    if (c == '\n') {

        return 1;
    }
    else {

        return 0;
    }
}