Latest and greatest

1 files changed, 955 insertions, 0 deletions

diff --git a/coreutils/tail.c b/coreutils/tail.c
new file mode 100644
index 000000000..058d462a5
--- /dev/null
+++ b/coreutils/tail.c
@@ -0,0 +1,955 @@
+/* tail -- output the last part of file(s)
+   Copyright (C) 89, 90, 91, 95, 1996 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* Can display any amount of data, unlike the Unix version, which uses
+   a fixed size buffer and therefore can only deliver a limited number
+   of lines.
+
+   Options:
+   -b			Tail by N 512-byte blocks.
+   -c, --bytes=N[bkm]	Tail by N bytes
+			[or 512-byte blocks, kilobytes, or megabytes].
+   -f, --follow		Loop forever trying to read more characters at the
+			end of the file, on the assumption that the file
+			is growing.  Ignored if reading from a pipe.
+   -n, --lines=N	Tail by N lines.
+   -q, --quiet, --silent	Never print filename headers.
+   -v, --verbose		Always print filename headers.
+
+   If a number (N) starts with a `+', begin printing with the Nth item
+   from the start of each file, instead of from the end.
+
+   Reads from standard input if no files are given or when a filename of
+   ``-'' is encountered.
+   By default, filename headers are printed only more than one file
+   is given.
+   By default, prints the last 10 lines (tail -n 10).
+
+   Original version by Paul Rubin <phr@ocf.berkeley.edu>.
+   Extensions by David MacKenzie <djm@gnu.ai.mit.edu>.
+   tail -f for multiple files by Ian Lance Taylor <ian@airs.com>.  */
+
+#include "internal.h"
+
+#include <stdio.h>
+#include <assert.h>
+#include <errno.h>
+#include <sys/types.h>
+
+
+/* Disable assertions.  Some systems have broken assert macros.  */
+#define NDEBUG 1
+
+
+static void error(int i, int errnum, char* fmt, const char *msg)
+{
+    fprintf(stderr, fmt, msg);
+    perror( errnum);
+    exit(i);
+}
+
+
+#define XWRITE(fd, buffer, n_bytes)					\
+  do									\
+    {									\
+      assert ((fd) == 1);						\
+      assert ((n_bytes) >= 0);						\
+      if (n_bytes > 0 && fwrite ((buffer), 1, (n_bytes), stdout) == 0)	\
+	error (EXIT_FAILURE, errno, "write error", NULL);			\
+    }									\
+  while (0)
+
+/* Number of items to tail.  */
+#define DEFAULT_N_LINES 10
+
+/* Size of atomic reads.  */
+#ifndef BUFSIZ
+#define BUFSIZ (512 * 8)
+#endif
+
+/* If nonzero, interpret the numeric argument as the number of lines.
+   Otherwise, interpret it as the number of bytes.  */
+static int count_lines;
+
+/* If nonzero, read from the end of one file until killed.  */
+static int forever;
+
+/* If nonzero, read from the end of multiple files until killed.  */
+static int forever_multiple;
+
+/* Array of file descriptors if forever_multiple is 1.  */
+static int *file_descs;
+
+/* Array of file sizes if forever_multiple is 1.  */
+static off_t *file_sizes;
+
+/* If nonzero, count from start of file instead of end.  */
+static int from_start;
+
+/* If nonzero, print filename headers.  */
+static int print_headers;
+
+/* When to print the filename banners.  */
+enum header_mode
+{
+  multiple_files, always, never
+};
+
+char *xmalloc ();
+int safe_read ();
+
+/* The name this program was run with.  */
+char *program_name;
+
+/* Nonzero if we have ever read standard input.  */
+static int have_read_stdin;
+
+/* If nonzero, display usage information and exit.  */
+static int show_help;
+
+/* If nonzero, print the version on standard output then exit.  */
+static int show_version;
+
+static const char tail_usage[] = 
+"tail [OPTION]... [FILE]...\n\
+Print last 10 lines of each FILE to standard output.\n\
+With more than one FILE, precede each with a header giving the file name.\n\
+With no FILE, or when FILE is -, read standard input.\n\
+\n\
+  -c, --bytes=N            output the last N bytes\n\
+  -f, --follow             output appended data as the file grows\n\
+  -n, --lines=N            output the last N lines, instead of last 10\n\
+  -q, --quiet, --silent    never output headers giving file names\n\
+  -v, --verbose            always output headers giving file names\n\
+      --help               display this help and exit\n\
+      --version            output version information and exit\n\
+\n\
+If the first character of N (the number of bytes or lines) is a `+',\n\
+print beginning with the Nth item from the start of each file, otherwise,\n\
+print the last N items in the file.  N may have a multiplier suffix:\n\
+b for 512, k for 1024, m for 1048576 (1 Meg).  A first OPTION of -VALUE\n\
+or +VALUE is treated like -n VALUE or -n +VALUE unless VALUE has one of\n\
+the [bkm] suffix multipliers, in which case it is treated like -c VALUE\n\
+or -c +VALUE.\n";
+
+static void
+write_header (const char *filename, const char *comment)
+{
+  static int first_file = 1;
+
+  printf ("%s==> %s%s%s <==\n", (first_file ? "" : "\n"), filename,
+	  (comment ? ": " : ""),
+	  (comment ? comment : ""));
+  first_file = 0;
+}
+
+/* Print the last N_LINES lines from the end of file FD.
+   Go backward through the file, reading `BUFSIZ' bytes at a time (except
+   probably the first), until we hit the start of the file or have
+   read NUMBER newlines.
+   POS starts out as the length of the file (the offset of the last
+   byte of the file + 1).
+   Return 0 if successful, 1 if an error occurred.  */
+
+static int
+file_lines (const char *filename, int fd, long int n_lines, off_t pos)
+{
+  char buffer[BUFSIZ];
+  int bytes_read;
+  int i;			/* Index into `buffer' for scanning.  */
+
+  if (n_lines == 0)
+    return 0;
+
+  /* Set `bytes_read' to the size of the last, probably partial, buffer;
+     0 < `bytes_read' <= `BUFSIZ'.  */
+  bytes_read = pos % BUFSIZ;
+  if (bytes_read == 0)
+    bytes_read = BUFSIZ;
+  /* Make `pos' a multiple of `BUFSIZ' (0 if the file is short), so that all
+     reads will be on block boundaries, which might increase efficiency.  */
+  pos -= bytes_read;
+  lseek (fd, pos, SEEK_SET);
+  bytes_read = safe_read (fd, buffer, bytes_read);
+  if (bytes_read == -1)
+    {
+      error (0, errno, "%s", filename);
+      return 1;
+    }
+
+  /* Count the incomplete line on files that don't end with a newline.  */
+  if (bytes_read && buffer[bytes_read - 1] != '\n')
+    --n_lines;
+
+  do
+    {
+      /* Scan backward, counting the newlines in this bufferfull.  */
+      for (i = bytes_read - 1; i >= 0; i--)
+	{
+	  /* Have we counted the requested number of newlines yet?  */
+	  if (buffer[i] == '\n' && n_lines-- == 0)
+	    {
+	      /* If this newline wasn't the last character in the buffer,
+	         print the text after it.  */
+	      if (i != bytes_read - 1)
+		XWRITE (STDOUT_FILENO, &buffer[i + 1], bytes_read - (i + 1));
+	      return 0;
+	    }
+	}
+      /* Not enough newlines in that bufferfull.  */
+      if (pos == 0)
+	{
+	  /* Not enough lines in the file; print the entire file.  */
+	  lseek (fd, (off_t) 0, SEEK_SET);
+	  return 0;
+	}
+      pos -= BUFSIZ;
+      lseek (fd, pos, SEEK_SET);
+    }
+  while ((bytes_read = safe_read (fd, buffer, BUFSIZ)) > 0);
+  if (bytes_read == -1)
+    {
+      error (0, errno, "%s", filename);
+      return 1;
+    }
+  return 0;
+}
+
+/* Print the last N_LINES lines from the end of the standard input,
+   open for reading as pipe FD.
+   Buffer the text as a linked list of LBUFFERs, adding them as needed.
+   Return 0 if successful, 1 if an error occured.  */
+
+static int
+pipe_lines (const char *filename, int fd, long int n_lines)
+{
+  struct linebuffer
+  {
+    int nbytes, nlines;
+    char buffer[BUFSIZ];
+    struct linebuffer *next;
+  };
+  typedef struct linebuffer LBUFFER;
+  LBUFFER *first, *last, *tmp;
+  int i;			/* Index into buffers.  */
+  int total_lines = 0;		/* Total number of newlines in all buffers.  */
+  int errors = 0;
+
+  first = last = (LBUFFER *) xmalloc (sizeof (LBUFFER));
+  first->nbytes = first->nlines = 0;
+  first->next = NULL;
+  tmp = (LBUFFER *) xmalloc (sizeof (LBUFFER));
+
+  /* Input is always read into a fresh buffer.  */
+  while ((tmp->nbytes = safe_read (fd, tmp->buffer, BUFSIZ)) > 0)
+    {
+      tmp->nlines = 0;
+      tmp->next = NULL;
+
+      /* Count the number of newlines just read.  */
+      for (i = 0; i < tmp->nbytes; i++)
+	if (tmp->buffer[i] == '\n')
+	  ++tmp->nlines;
+      total_lines += tmp->nlines;
+
+      /* If there is enough room in the last buffer read, just append the new
+         one to it.  This is because when reading from a pipe, `nbytes' can
+         often be very small.  */
+      if (tmp->nbytes + last->nbytes < BUFSIZ)
+	{
+	  memcpy (&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes);
+	  last->nbytes += tmp->nbytes;
+	  last->nlines += tmp->nlines;
+	}
+      else
+	{
+	  /* If there's not enough room, link the new buffer onto the end of
+	     the list, then either free up the oldest buffer for the next
+	     read if that would leave enough lines, or else malloc a new one.
+	     Some compaction mechanism is possible but probably not
+	     worthwhile.  */
+	  last = last->next = tmp;
+	  if (total_lines - first->nlines > n_lines)
+	    {
+	      tmp = first;
+	      total_lines -= first->nlines;
+	      first = first->next;
+	    }
+	  else
+	    tmp = (LBUFFER *) xmalloc (sizeof (LBUFFER));
+	}
+    }
+  if (tmp->nbytes == -1)
+    {
+      error (0, errno, "%s", filename);
+      errors = 1;
+      free ((char *) tmp);
+      goto free_lbuffers;
+    }
+
+  free ((char *) tmp);
+
+  /* This prevents a core dump when the pipe contains no newlines.  */
+  if (n_lines == 0)
+    goto free_lbuffers;
+
+  /* Count the incomplete line on files that don't end with a newline.  */
+  if (last->buffer[last->nbytes - 1] != '\n')
+    {
+      ++last->nlines;
+      ++total_lines;
+    }
+
+  /* Run through the list, printing lines.  First, skip over unneeded
+     buffers.  */
+  for (tmp = first; total_lines - tmp->nlines > n_lines; tmp = tmp->next)
+    total_lines -= tmp->nlines;
+
+  /* Find the correct beginning, then print the rest of the file.  */
+  if (total_lines > n_lines)
+    {
+      char *cp;
+
+      /* Skip `total_lines' - `n_lines' newlines.  We made sure that
+         `total_lines' - `n_lines' <= `tmp->nlines'.  */
+      cp = tmp->buffer;
+      for (i = total_lines - n_lines; i; --i)
+	while (*cp++ != '\n')
+	  /* Do nothing.  */ ;
+      i = cp - tmp->buffer;
+    }
+  else
+    i = 0;
+  XWRITE (STDOUT_FILENO, &tmp->buffer[i], tmp->nbytes - i);
+
+  for (tmp = tmp->next; tmp; tmp = tmp->next)
+    XWRITE (STDOUT_FILENO, tmp->buffer, tmp->nbytes);
+
+free_lbuffers:
+  while (first)
+    {
+      tmp = first->next;
+      free ((char *) first);
+      first = tmp;
+    }
+  return errors;
+}
+
+/* Print the last N_BYTES characters from the end of pipe FD.
+   This is a stripped down version of pipe_lines.
+   Return 0 if successful, 1 if an error occurred.  */
+
+static int
+pipe_bytes (const char *filename, int fd, off_t n_bytes)
+{
+  struct charbuffer
+  {
+    int nbytes;
+    char buffer[BUFSIZ];
+    struct charbuffer *next;
+  };
+  typedef struct charbuffer CBUFFER;
+  CBUFFER *first, *last, *tmp;
+  int i;			/* Index into buffers.  */
+  int total_bytes = 0;		/* Total characters in all buffers.  */
+  int errors = 0;
+
+  first = last = (CBUFFER *) xmalloc (sizeof (CBUFFER));
+  first->nbytes = 0;
+  first->next = NULL;
+  tmp = (CBUFFER *) xmalloc (sizeof (CBUFFER));
+
+  /* Input is always read into a fresh buffer.  */
+  while ((tmp->nbytes = safe_read (fd, tmp->buffer, BUFSIZ)) > 0)
+    {
+      tmp->next = NULL;
+
+      total_bytes += tmp->nbytes;
+      /* If there is enough room in the last buffer read, just append the new
+         one to it.  This is because when reading from a pipe, `nbytes' can
+         often be very small.  */
+      if (tmp->nbytes + last->nbytes < BUFSIZ)
+	{
+	  memcpy (&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes);
+	  last->nbytes += tmp->nbytes;
+	}
+      else
+	{
+	  /* If there's not enough room, link the new buffer onto the end of
+	     the list, then either free up the oldest buffer for the next
+	     read if that would leave enough characters, or else malloc a new
+	     one.  Some compaction mechanism is possible but probably not
+	     worthwhile.  */
+	  last = last->next = tmp;
+	  if (total_bytes - first->nbytes > n_bytes)
+	    {
+	      tmp = first;
+	      total_bytes -= first->nbytes;
+	      first = first->next;
+	    }
+	  else
+	    {
+	      tmp = (CBUFFER *) xmalloc (sizeof (CBUFFER));
+	    }
+	}
+    }
+  if (tmp->nbytes == -1)
+    {
+      error (0, errno, "%s", filename);
+      errors = 1;
+      free ((char *) tmp);
+      goto free_cbuffers;
+    }
+
+  free ((char *) tmp);
+
+  /* Run through the list, printing characters.  First, skip over unneeded
+     buffers.  */
+  for (tmp = first; total_bytes - tmp->nbytes > n_bytes; tmp = tmp->next)
+    total_bytes -= tmp->nbytes;
+
+  /* Find the correct beginning, then print the rest of the file.
+     We made sure that `total_bytes' - `n_bytes' <= `tmp->nbytes'.  */
+  if (total_bytes > n_bytes)
+    i = total_bytes - n_bytes;
+  else
+    i = 0;
+  XWRITE (STDOUT_FILENO, &tmp->buffer[i], tmp->nbytes - i);
+
+  for (tmp = tmp->next; tmp; tmp = tmp->next)
+    XWRITE (STDOUT_FILENO, tmp->buffer, tmp->nbytes);
+
+free_cbuffers:
+  while (first)
+    {
+      tmp = first->next;
+      free ((char *) first);
+      first = tmp;
+    }
+  return errors;
+}
+
+/* Skip N_BYTES characters from the start of pipe FD, and print
+   any extra characters that were read beyond that.
+   Return 1 on error, 0 if ok.  */
+
+static int
+start_bytes (const char *filename, int fd, off_t n_bytes)
+{
+  char buffer[BUFSIZ];
+  int bytes_read = 0;
+
+  while (n_bytes > 0 && (bytes_read = safe_read (fd, buffer, BUFSIZ)) > 0)
+    n_bytes -= bytes_read;
+  if (bytes_read == -1)
+    {
+      error (0, errno, "%s", filename);
+      return 1;
+    }
+  else if (n_bytes < 0)
+    XWRITE (STDOUT_FILENO, &buffer[bytes_read + n_bytes], -n_bytes);
+  return 0;
+}
+
+/* Skip N_LINES lines at the start of file or pipe FD, and print
+   any extra characters that were read beyond that.
+   Return 1 on error, 0 if ok.  */
+
+static int
+start_lines (const char *filename, int fd, long int n_lines)
+{
+  char buffer[BUFSIZ];
+  int bytes_read = 0;
+  int bytes_to_skip = 0;
+
+  while (n_lines && (bytes_read = safe_read (fd, buffer, BUFSIZ)) > 0)
+    {
+      bytes_to_skip = 0;
+      while (bytes_to_skip < bytes_read)
+	if (buffer[bytes_to_skip++] == '\n' && --n_lines == 0)
+	  break;
+    }
+  if (bytes_read == -1)
+    {
+      error (0, errno, "%s", filename);
+      return 1;
+    }
+  else if (bytes_to_skip < bytes_read)
+    {
+      XWRITE (STDOUT_FILENO, &buffer[bytes_to_skip],
+	      bytes_read - bytes_to_skip);
+    }
+  return 0;
+}
+
+/* Display file FILENAME from the current position in FD to the end.
+   If `forever' is nonzero, keep reading from the end of the file
+   until killed.  Return the number of bytes read from the file.  */
+
+static long
+dump_remainder (const char *filename, int fd)
+{
+  char buffer[BUFSIZ];
+  int bytes_read;
+  long total;
+
+  total = 0;
+output:
+  while ((bytes_read = safe_read (fd, buffer, BUFSIZ)) > 0)
+    {
+      XWRITE (STDOUT_FILENO, buffer, bytes_read);
+      total += bytes_read;
+    }
+  if (bytes_read == -1)
+    error (EXIT_FAILURE, errno, "%s", filename);
+  if (forever)
+    {
+      fflush (stdout);
+      sleep (1);
+      goto output;
+    }
+  else
+    {
+      if (forever_multiple)
+	fflush (stdout);
+    }
+
+  return total;
+}
+
+/* Tail NFILES (>1) files forever until killed.  The file names are in
+   NAMES.  The open file descriptors are in `file_descs', and the size
+   at which we stopped tailing them is in `file_sizes'.  We loop over
+   each of them, doing an fstat to see if they have changed size.  If
+   none of them have changed size in one iteration, we sleep for a
+   second and try again.  We do this until the user interrupts us.  */
+
+static void
+tail_forever (char **names, int nfiles)
+{
+  int last;
+
+  last = -1;
+
+  while (1)
+    {
+      int i;
+      int changed;
+
+      changed = 0;
+      for (i = 0; i < nfiles; i++)
+	{
+	  struct stat stats;
+
+	  if (file_descs[i] < 0)
+	    continue;
+	  if (fstat (file_descs[i], &stats) < 0)
+	    {
+	      error (0, errno, "%s", names[i]);
+	      file_descs[i] = -1;
+	      continue;
+	    }
+	  if (stats.st_size == file_sizes[i])
+	    continue;
+
+	  /* This file has changed size.  Print out what we can, and
+	     then keep looping.  */
+
+	  changed = 1;
+
+	  if (stats.st_size < file_sizes[i])
+	    {
+	      write_header (names[i], "file truncated");
+	      last = i;
+	      lseek (file_descs[i], stats.st_size, SEEK_SET);
+	      file_sizes[i] = stats.st_size;
+	      continue;
+	    }
+
+	  if (i != last)
+	    {
+	      if (print_headers)
+		write_header (names[i], NULL);
+	      last = i;
+	    }
+	  file_sizes[i] += dump_remainder (names[i], file_descs[i]);
+	}
+
+      /* If none of the files changed size, sleep.  */
+      if (! changed)
+	sleep (1);
+    }
+}
+
+/* Output the last N_BYTES bytes of file FILENAME open for reading in FD.
+   Return 0 if successful, 1 if an error occurred.  */
+
+static int
+tail_bytes (const char *filename, int fd, off_t n_bytes)
+{
+  struct stat stats;
+
+  /* FIXME: resolve this like in dd.c.  */
+  /* Use fstat instead of checking for errno == ESPIPE because
+     lseek doesn't work on some special files but doesn't return an
+     error, either.  */
+  if (fstat (fd, &stats))
+    {
+      error (0, errno, "%s", filename);
+      return 1;
+    }
+
+  if (from_start)
+    {
+      if (S_ISREG (stats.st_mode))
+	lseek (fd, n_bytes, SEEK_CUR);
+      else if (start_bytes (filename, fd, n_bytes))
+	return 1;
+      dump_remainder (filename, fd);
+    }
+  else
+    {
+      if (S_ISREG (stats.st_mode))
+	{
+	  off_t current_pos, end_pos;
+	  size_t bytes_remaining;
+
+	  if ((current_pos = lseek (fd, (off_t) 0, SEEK_CUR)) != -1
+	      && (end_pos = lseek (fd, (off_t) 0, SEEK_END)) != -1)
+	    {
+	      off_t diff;
+	      /* Be careful here.  The current position may actually be
+		 beyond the end of the file.  */
+	      bytes_remaining = (diff = end_pos - current_pos) < 0 ? 0 : diff;
+	    }
+	  else
+	    {
+	      error (0, errno, "%s", filename);
+	      return 1;
+	    }
+
+	  if (bytes_remaining <= n_bytes)
+	    {
+	      /* From the current position to end of file, there are no
+		 more bytes than have been requested.  So reposition the
+		 file pointer to the incoming current position and print
+		 everything after that.  */
+	      lseek (fd, current_pos, SEEK_SET);
+	    }
+	  else
+	    {
+	      /* There are more bytes remaining than were requested.
+		 Back up.  */
+	      lseek (fd, -n_bytes, SEEK_END);
+	    }
+	  dump_remainder (filename, fd);
+	}
+      else
+	return pipe_bytes (filename, fd, n_bytes);
+    }
+  return 0;
+}
+
+/* Output the last N_LINES lines of file FILENAME open for reading in FD.
+   Return 0 if successful, 1 if an error occurred.  */
+
+static int
+tail_lines (const char *filename, int fd, long int n_lines)
+{
+  struct stat stats;
+  off_t length;
+
+  if (fstat (fd, &stats))
+    {
+      error (0, errno, "%s", filename);
+      return 1;
+    }
+
+  if (from_start)
+    {
+      if (start_lines (filename, fd, n_lines))
+	return 1;
+      dump_remainder (filename, fd);
+    }
+  else
+    {
+      /* Use file_lines only if FD refers to a regular file with
+         its file pointer positioned at beginning of file.  */
+      /* FIXME: adding the lseek conjunct is a kludge.
+	 Once there's a reasonable test suite, fix the true culprit:
+	 file_lines.  file_lines shouldn't presume that the input
+	 file pointer is initially positioned to beginning of file.  */
+      if (S_ISREG (stats.st_mode)
+	  && lseek (fd, (off_t) 0, SEEK_CUR) == (off_t) 0)
+	{
+	  length = lseek (fd, (off_t) 0, SEEK_END);
+	  if (length != 0 && file_lines (filename, fd, n_lines, length))
+	    return 1;
+	  dump_remainder (filename, fd);
+	}
+      else
+	return pipe_lines (filename, fd, n_lines);
+    }
+  return 0;
+}
+
+/* Display the last N_UNITS units of file FILENAME, open for reading
+   in FD.
+   Return 0 if successful, 1 if an error occurred.  */
+
+static int
+tail (const char *filename, int fd, off_t n_units)
+{
+  if (count_lines)
+    return tail_lines (filename, fd, (long) n_units);
+  else
+    return tail_bytes (filename, fd, n_units);
+}
+
+/* Display the last N_UNITS units of file FILENAME.
+   "-" for FILENAME means the standard input.
+   FILENUM is this file's index in the list of files the user gave.
+   Return 0 if successful, 1 if an error occurred.  */
+
+static int
+tail_file (const char *filename, off_t n_units, int filenum)
+{
+  int fd, errors;
+  struct stat stats;
+
+  if (!strcmp (filename, "-")
+    {
+      have_read_stdin = 1;
+      filename = "standard input";
+      if (print_headers)
+	write_header (filename, NULL);
+      errors = tail (filename, 0, n_units);
+      if (forever_multiple)
+	{
+	  if (fstat (0, &stats) < 0)
+	    {
+	      error (0, errno, "standard input");
+	      errors = 1;
+	    }
+	  else if (!S_ISREG (stats.st_mode))
+	    {
+	      error (0, 0,
+		     "standard input: cannot follow end of non-regular file");
+	      errors = 1;
+	    }
+	  if (errors)
+	    file_descs[filenum] = -1;
+	  else
+	    {
+	      file_descs[filenum] = 0;
+	      file_sizes[filenum] = stats.st_size;
+	    }
+	}
+    }
+  else
+    {
+      /* Not standard input.  */
+      fd = open (filename, O_RDONLY);
+      if (fd == -1)
+	{
+	  if (forever_multiple)
+	    file_descs[filenum] = -1;
+	  error (0, errno, "%s", filename);
+	  errors = 1;
+	}
+      else
+	{
+	  if (print_headers)
+	    write_header (filename, NULL);
+	  errors = tail (filename, fd, n_units);
+	  if (forever_multiple)
+	    {
+	      if (fstat (fd, &stats) < 0)
+		{
+		  error (0, errno, "%s", filename);
+		  errors = 1;
+		}
+	      else if (!S_ISREG (stats.st_mode))
+		{
+		  error (0, 0, "%s: cannot follow end of non-regular file",
+			 filename);
+		  errors = 1;
+		}
+	      if (errors)
+		{
+		  close (fd);
+		  file_descs[filenum] = -1;
+		}
+	      else
+		{
+		  file_descs[filenum] = fd;
+		  file_sizes[filenum] = stats.st_size;
+		}
+	    }
+	  else
+	    {
+	      if (close (fd))
+		{
+		  error (0, errno, "%s", filename);
+		  errors = 1;
+		}
+	    }
+	}
+    }
+
+  return errors;
+}
+
+extern int
+tai_main (int argc, char **argv)
+{
+  enum header_mode header_mode = multiple_files;
+  int exit_status = 0;
+  /* If from_start, the number of items to skip before printing; otherwise,
+     the number of items at the end of the file to print.  Initially, -1
+     means the value has not been set.  */
+  off_t n_units = -1;
+  long int tmp_long;
+  int c;			/* Option character.  */
+  int n_files;
+  char **file;
+
+  program_name = argv[0];
+  have_read_stdin = 0;
+  count_lines = 1;
+  forever = forever_multiple = from_start = print_headers = 0;
+
+  if (argc > 1
+      && ((argv[1][0] == '-' && ISDIGIT (argv[1][1]))
+	  || (argv[1][0] == '+' && (ISDIGIT (argv[1][1])
+				    || argv[1][1] == 0))))
+    {
+      /* Old option syntax: a dash or plus, one or more digits (zero digits
+	 are acceptable with a plus), and one or more option letters.  */
+      if (argv[1][0] == '+')
+	from_start = 1;
+      if (argv[1][1] != '\0')
+	{
+	  strtol_error s_err;
+	  char *p;
+
+	  s_err = xstrtol (++argv[1], &p, 0, &tmp_long, "bkm");
+	  n_units = tmp_long;
+	  if (s_err == LONGINT_OVERFLOW)
+	    {
+	      STRTOL_FATAL_ERROR (argv[1], "argument", s_err);
+	    }
+
+	  /* If a [bkm] suffix was given then count bytes, not lines.  */
+	  if (p[-1] == 'b' || p[-1] == 'k' || p[-1] == 'm')
+	    count_lines = 0;
+
+	  /* Parse any appended option letters.  */
+	  while (*p)
+	    {
+	      switch (*p)
+		{
+		case 'c':
+		  /* Interpret N_UNITS as # of bytes.  */
+		  count_lines = 0;
+		  break;
+
+		case 'f':
+		  forever = 1;
+		  break;
+
+		case 'l':
+		  count_lines = 1;
+		  break;
+
+		case 'q':
+		  header_mode = never;
+		  break;
+
+		case 'v':
+		  header_mode = always;
+		  break;
+
+		default:
+		  error (0, 0, "unrecognized option '%c'", *p);
+		  usage (tail_usage);
+		}
+	      ++p;
+	    }
+	}
+      /* Make the options we just parsed invisible to getopt.  */
+      argv[1] = argv[0];
+      argv++;
+      argc--;
+    }
+
+  if (show_version)
+    {
+      printf ("tail - %s\n", PACKAGE_VERSION);
+      exit (EXIT_SUCCESS);
+    }
+
+  if (show_help)
+    usage (tail_usage);
+
+  if (n_units == -1)
+    n_units = DEFAULT_N_LINES;
+
+  /* To start printing with item N_UNITS from the start of the file, skip
+     N_UNITS - 1 items.  `tail +0' is actually meaningless, but for Unix
+     compatibility it's treated the same as `tail +1'.  */
+  if (from_start)
+    {
+      if (n_units)
+	--n_units;
+    }
+
+  n_files = argc - optind;
+  file = argv + optind;
+
+  if (n_files > 1 && forever)
+    {
+      forever_multiple = 1;
+      forever = 0;
+      file_descs = (int *) xmalloc (n_files * sizeof (int));
+      file_sizes = (off_t *) xmalloc (n_files * sizeof (off_t));
+    }
+
+  if (header_mode == always
+      || (header_mode == multiple_files && n_files > 1))
+    print_headers = 1;
+
+  if (n_files == 0)
+    {
+      exit_status |= tail_file ("-", n_units, 0);
+    }
+  else
+    {
+      int i;
+      for (i = 0; i < n_files; i++)
+	exit_status |= tail_file (file[i], n_units, i);
+
+      if (forever_multiple)
+	tail_forever (file, n_files);
+    }
+
+  if (have_read_stdin && close (0) < 0)
+    error (EXIT_FAILURE, errno, "-");
+  if (fclose (stdout) == EOF)
+    error (EXIT_FAILURE, errno, "write error");
+  exit (exit_status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
+}