printLongestLine.c

#include <stdio.h>

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

/* In the book, this function is called 'getline' but due to
   conflicts with the 'getline' function in stdio.h, we
   prepend an underscore here. */
int _getline(char line[], int maxline);
void copy(char to[], char from[]);

/* print 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("length: %d, line: %s", max, 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';

    /* If it was the line limit that stopped previous iteration,
       then keep counting until it is an EOF or newline. */
    if (c != EOF && c != '\n')
        i++;
    while ((c = getchar()) != EOF && c != '\n')
        i++;

    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;
}