tail -1

tail.c

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

#define BUF 4096

int main(int argc, char **argv)
{
    FILE *f;
    int i, n, nl;
    long o1, o2;
    char buf[BUF];
    if (argc != 2)
        return 1;

    f = fopen(argv[1], "rb");
    fseek(f, 0, SEEK_END);
    o1 = (o1 = ftell(f)) < BUF ? o1 : BUF;

    for (o2 = 0;;) {
        fseek(f, o2 -= o1, SEEK_END);
        fread(buf, 1, o1, f);
        for (i = 0, n = -1; i < o1; ++i)
            if (buf[i] == '\n')
                nl = n, n = i;
        if (n != -1)
            break;
    }

out:
    {
        char *l = malloc(n = -(o2 + nl) + 1);
        fseek(f, (o2 + nl) + 1, SEEK_END);
        fread(l, 1, n - 1, f);
        l[n-1] = '\0';
        printf("%s", l);
    }


    return 0;
}