#!/usr/bin/env compileAndGo
# See http://Yost.com/computers/compileAndGo
compiler = gcc
compileAndGo

/* tac.c -- Author unknown */
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>

/* changed from LENGTH to larger number -dyost 870619 */
/* 2005-08-05 also digest old-style Mac files with \r line endings -dyost */
#define LENGTH (1000 * 1024)

main(argc, argv)
int	argc;
char	**argv;
{
  off_t           off, lseek();
  static char     buffer[ 1 + LENGTH + LENGTH + 1 ];
  char            *buf;
  char            *readerr = "Read error at offset %lu of %s\n";
  int             fd, any;
  void            output(), utcopyn();

  if (argc < 2) {
    (void) fprintf(stderr, "Usage: tac file ...\n");
    exit(1);
  }

  buf = buffer;
  *buf++ = '\n';

  any = 0;
  while (--argc) {
    register int i;

    {
      register char   *filename;

      {
        struct  stat st;

        if (stat(filename = *++argv, &st) == -1) {
          (void) fprintf(stderr , "Bad status for %s\n", filename);
          any++;
          continue;
        }
        if ((off = st.st_size) == 0) continue;
      }
      if ((fd = open(filename, 0)) == -1) {
        (void) fprintf(stderr, "Can't open %s\n", filename);
        any++;
        continue;
      }

      if ((i = off % LENGTH ) == 0) i = LENGTH;
      off -= i;

      if (lseek(fd, off, 0) < 0) {
        (void) fprintf(stderr, "Can't seek to end of %s\n", filename);
        (void) close(fd);
        any++;
        continue;
      }
      if (read(fd, buf, i) != i) {
        (void) fprintf(stderr, readerr, off, filename);
        (void) close(fd);
        any++;
        continue;
      }
    }

    {
      register char *begin;
      register char *end;

      begin = end = buf + i;
      if (*--begin == '\n' || *begin == '\r') end = begin;

      for (;;) {
        while (*--begin != '\n' && *begin != '\r') continue;
        if (begin < buf) {
          if (off == 0) {
            output(begin, end);
            (void) close(fd);
            break;
          }
          (void) lseek(fd, off -= LENGTH, 0);
          if ((i = end - buf) > LENGTH) {
            (void) fprintf(stderr, "Line too long\n");
            any++;
            i = LENGTH;
          }
          utcopyn(begin = buf + LENGTH, buf, i);
          end = begin + i;
          if (read(fd, buf, LENGTH) != LENGTH) {
            (void) fprintf(stderr, readerr, off, *argv);
            any++;
            (void) close(fd);
            break;
          }
          continue;
        }
        output(begin, end);
        end = begin;
      }
    }
  }
  exit(any);
}

void
output(
  register char* begin,
  register char* end
)
{
  register FILE *iop = stdout;

  for (begin++; begin < end; ++begin)
    (void) putc(*begin, iop);
  (void) putc('\n', iop);
  fflush (iop);
}

void
utcopyn(tp, fp, n)
register char *tp, *fp;
register int n;
{
  while (--n >= 0) *tp++ = *fp++;
  return;
}