(do_link): Produce the same sort of one-line output for

[coreutils.git] / src / sort.c

/* sort - sort lines of text (with all kinds of options).
   Copyright (C) 88, 1991-1999 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.

   Written December 1988 by Mike Haertel.
   The author may be reached (Email) at the address mike@gnu.ai.mit.edu,
   or (US mail) as Mike Haertel c/o Free Software Foundation.

   Ørn E. Hansen added NLS support in 1997.  */

#include <config.h>

#include <sys/types.h>
#include <signal.h>
#include <stdio.h>
#include <assert.h>
#include "system.h"
#include "long-options.h"
#include "error.h"
#include "hard-locale.h"
#include "memcoll.h"
#include "xalloc.h"

/* The official name of this program (e.g., no `g' prefix).  */
#define PROGRAM_NAME "sort"

#define AUTHORS "Mike Haertel"

#if defined ENABLE_NLS && HAVE_LANGINFO_H
# include <langinfo.h>
#endif

#if HAVE_PATHCONF && defined _PC_NAME_MAX
# define NAME_MAX_IN_DIR(Dir) pathconf (Dir, _PC_NAME_MAX)
#else
# define NAME_MAX_IN_DIR(Dir) 255
#endif

#ifndef STDC_HEADERS
double strtod ();
#endif

/* Undefine, to avoid warning about redefinition on some systems.  */
#undef min
#define min(a, b) ((a) < (b) ? (a) : (b))
#undef max
#define max(a, b) ((a) > (b) ? (a) : (b))

#define UCHAR_LIM (UCHAR_MAX + 1)
#define UCHAR(c) ((unsigned char) (c))

#ifndef DEFAULT_TMPDIR
# define DEFAULT_TMPDIR "/tmp"
#endif

/* Use this as exit status in case of error, not EXIT_FAILURE.  This
   is necessary because EXIT_FAILURE is usually 1 and POSIX requires
   that sort exit with status 1 IFF invoked with -c and the input is
   not properly sorted.  Any other irregular exit must exit with a
   status code greater than 1.  */
#define SORT_FAILURE 2

#define C_DECIMAL_POINT '.'
#define NEGATION_SIGN   '-'
#define NUMERIC_ZERO    '0'

#ifdef ENABLE_NLS

static char decimal_point;
static int th_sep; /* if CHAR_MAX + 1, then there is no thousands separator */

/* Nonzero if the corresponding locales are hard.  */
static int hard_LC_COLLATE;
static int hard_LC_CTYPE;
# if HAVE_NL_LANGINFO
static int hard_LC_TIME;
# endif

# define IS_THOUSANDS_SEP(x) ((x) == th_sep)

#else

# define decimal_point C_DECIMAL_POINT
# define IS_THOUSANDS_SEP(x) 0

#endif

/* The kind of blanks for '-b' to skip in various options. */
enum blanktype { bl_start, bl_end, bl_both };

/* The character marking end of line. Default to \n. */
int eolchar = '\n';

/* Lines are held in core as counted strings. */
struct line
{
  char *text;                   /* Text of the line. */
  int length;                   /* Length including final newline. */
  char *keybeg;                 /* Start of first key. */
  char *keylim;                 /* Limit of first key. */
};

/* Arrays of lines. */
struct lines
{
  struct line *lines;           /* Dynamically allocated array of lines. */
  int used;                     /* Number of slots used. */
  int alloc;                    /* Number of slots allocated. */
  int limit;                    /* Max number of slots to allocate.  */
};

/* Input buffers. */
struct buffer
{
  char *buf;                    /* Dynamically allocated buffer. */
  int used;                     /* Number of bytes used. */
  int alloc;                    /* Number of bytes allocated. */
  int left;                     /* Number of bytes left after line parsing. */
};

struct keyfield
{
  int sword;                    /* Zero-origin 'word' to start at. */
  int schar;                    /* Additional characters to skip. */
  int skipsblanks;              /* Skip leading white space at start. */
  int eword;                    /* Zero-origin first word after field. */
  int echar;                    /* Additional characters in field. */
  int skipeblanks;              /* Skip trailing white space at finish. */
  int *ignore;                  /* Boolean array of characters to ignore. */
  char *translate;              /* Translation applied to characters. */
  int numeric;                  /* Flag for numeric comparison.  Handle
                                   strings of digits with optional decimal
                                   point, but no exponential notation. */
  int general_numeric;          /* Flag for general, numeric comparison.
                                   Handle numbers in exponential notation. */
  int month;                    /* Flag for comparison by month name. */
  int reverse;                  /* Reverse the sense of comparison. */
  struct keyfield *next;        /* Next keyfield to try. */
};

struct month
{
  char *name;
  int val;
};

/* The name this program was run with. */
char *program_name;

/* Table of white space. */
static int blanks[UCHAR_LIM];

/* Table of non-printing characters. */
static int nonprinting[UCHAR_LIM];

/* Table of non-dictionary characters (not letters, digits, or blanks). */
static int nondictionary[UCHAR_LIM];

/* Translation table folding lower case to upper.
   FIXME: This doesn't work with multibyte character sets.  */
static char fold_toupper[UCHAR_LIM];

#define MONTHS_PER_YEAR 12

#if defined ENABLE_NLS && HAVE_NL_LANGINFO
# define MONTHTAB_CONST /* empty */
#else
# define MONTHTAB_CONST const
#endif

/* Table mapping month names to integers.
   Alphabetic order allows binary search. */
static MONTHTAB_CONST struct month monthtab[] =
{
  {"APR", 4},
  {"AUG", 8},
  {"DEC", 12},
  {"FEB", 2},
  {"JAN", 1},
  {"JUL", 7},
  {"JUN", 6},
  {"MAR", 3},
  {"MAY", 5},
  {"NOV", 11},
  {"OCT", 10},
  {"SEP", 9}
};

/* During the merge phase, the number of files to merge at once. */
#define NMERGE 16

/* Initial buffer size for in-core sorting.  The buffer will grow only
   if a line longer than this is seen. */
#define SORTALLOC (8 * 1024 * 1024)
static int const sortalloc = SORTALLOC;

/* Initial buffer size for in core merge buffers.  Bear in mind that
   up to NMERGE * mergealloc bytes may be allocated for merge buffers. */
static int const mergealloc = SORTALLOC / NMERGE / 2;

/* Guess of average line length. */
static int const linelength = 30;

/* Maximum number of elements for the array(s) of struct line's, in bytes.  */
#define LINEALLOC (SORTALLOC / 2)

/* Directory in which any temporary files are to be created. */
static char *temp_dir;

/* Flag to reverse the order of all comparisons. */
static int reverse;

/* Flag for stable sort.  This turns off the last ditch bytewise
   comparison of lines, and instead leaves lines in the same order
   they were read if all keys compare equal.  */
static int stable;

/* Tab character separating fields.  If NUL, then fields are separated
   by the empty string between a non-whitespace character and a whitespace
   character. */
static char tab;

/* Flag to remove consecutive duplicate lines from the output.
   Only the last of a sequence of equal lines will be output. */
static int unique;

/* Nonzero if any of the input files are the standard input. */
static int have_read_stdin;

/* Lists of key field comparisons to be tried. */
static struct keyfield keyhead;

void
usage (int status)
{
  if (status != 0)
    fprintf (stderr, _("Try `%s --help' for more information.\n"),
             program_name);
  else
    {
      printf (_("\
Usage: %s [OPTION]... [FILE]...\n\
"),
              program_name);
      printf (_("\
Write sorted concatenation of all FILE(s) to standard output.\n\
\n\
  +POS1 [-POS2]    start a key at POS1, end it *before* POS2 (obsolescent)\n\
                     field numbers and character offsets are numbered\n\
                     starting with zero (contrast with the -k option)\n\
  -b               ignore leading blanks in sort fields or keys\n\
  -c               check if given files already sorted, do not sort\n\
  -d               consider only [a-zA-Z0-9 ] characters in keys\n\
  -f               fold lower case to upper case characters in keys\n\
  -g               compare according to general numerical value, imply -b\n\
  -i               consider only [\\040-\\0176] characters in keys\n\
  -k POS1[,POS2]   start a key at POS1, end it *at* POS2\n\
                     field numbers and character offsets are numbered\n\
                     starting with one (contrast with zero-based +POS form)\n\
  -m               merge already sorted files, do not sort\n\
  -M               compare (unknown) < `JAN' < ... < `DEC', imply -b\n\
  -n               compare according to string numerical value, imply -b\n\
  -o FILE          write result on FILE instead of standard output\n\
  -r               reverse the result of comparisons\n\
  -s               stabilize sort by disabling last resort comparison\n\
  -t SEP           use SEParator instead of non- to whitespace transition\n\
  -T DIRECTORY     use DIRECTORY for temporary files, not $TMPDIR or %s\n\
  -u               with -c, check for strict ordering;\n\
                   with -m, only output the first of an equal sequence\n\
  -z               end lines with 0 byte, not newline, for find -print0\n\
      --help       display this help and exit\n\
      --version    output version information and exit\n\
\n\
"),
              DEFAULT_TMPDIR);
      printf (_("\
POS is F[.C][OPTS], where F is the field number and C the character position\n\
in the field, both counted from one with -k, from zero with the obsolescent\n\
form.  OPTS is made up of one or more of Mbdfinr; this effectively disables\n\
global -Mbdfinr settings for that key.  If no key is given, use the entire\n\
line as the key.  With no FILE, or when FILE is -, read standard input.\n\
")
              );
      puts (_("\nReport bugs to <bug-textutils@gnu.org>."));
    }
  /* Don't use EXIT_FAILURE here in case it is defined to be 1.
     POSIX requires that sort return 1 IFF invoked with -c and
     the input is not properly sorted.  */
  assert (status == 0 || status == SORT_FAILURE);
  exit (status);
}

/* The list of temporary files. */
static struct tempnode
{
  char *name;
  struct tempnode *next;
} temphead;

/* Clean up any remaining temporary files. */

static void
cleanup (void)
{
  struct tempnode *node;

  for (node = temphead.next; node; node = node->next)
    unlink (node->name);
}

static FILE *
xtmpfopen (const char *file)
{
  FILE *fp;
  int fd;

  /*  Open temporary file exclusively, to foil a common
      denial-of-service attack.  */
  fd = open (file, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL, 0600);
  if (fd < 0 || (fp = fdopen (fd, "w")) == NULL)
    {
      error (0, errno, "%s", file);
      cleanup ();
      exit (SORT_FAILURE);
    }

  return fp;
}

static FILE *
xfopen (const char *file, const char *how)
{
  FILE *fp;

  if (STREQ (file, "-"))
    {
      fp = stdin;
    }
  else
    {
      if ((fp = fopen (file, how)) == NULL)
        {
          error (0, errno, "%s", file);
          cleanup ();
          exit (SORT_FAILURE);
        }
    }

  if (fp == stdin)
    have_read_stdin = 1;
  return fp;
}

static void
xfclose (FILE *fp)
{
  if (fp == stdin)
    {
      /* Allow reading stdin from tty more than once. */
      if (feof (fp))
        clearerr (fp);
    }
  else if (fp == stdout)
    {
      if (fflush (fp) != 0)
        {
          error (0, errno, _("flushing file"));
          cleanup ();
          exit (SORT_FAILURE);
        }
    }
  else
    {
      if (fclose (fp) != 0)
        {
          error (0, errno, _("error closing file"));
          cleanup ();
          exit (SORT_FAILURE);
        }
    }
}

static void
write_bytes (const char *buf, size_t n_bytes, FILE *fp, const char *output_file)
{
  if (fwrite (buf, 1, n_bytes, fp) != n_bytes)
    {
      error (0, errno, _("%s: write error"), output_file);
      cleanup ();
      exit (SORT_FAILURE);
    }
}

/* Return a name for a temporary file. */

static char *
tempname (void)
{
  static unsigned int seq;
  int len = strlen (temp_dir);
  char *name = xmalloc (len + 1 + sizeof ("sort") - 1 + 5 + 5 + 1);
  int long_file_names = NAME_MAX_IN_DIR (temp_dir) > 12;
  struct tempnode *node;

  /* If long filenames aren't supported, we cannot use filenames
     longer than 8+3 and still assume they are unique.  */
  if (long_file_names)
    sprintf (name,
             "%s%ssort%5.5d%5.5d",
             temp_dir,
             (len && temp_dir[len - 1] != '/') ? "/" : "",
             (unsigned int) getpid () & 0xffff, seq);
  else
    sprintf (name, "%s%ss%5.5d%2.2d.%3.3d",
             temp_dir,
             (len && temp_dir[len - 1] != '/') ? "/" : "",
             (unsigned int) getpid () & 0xffff, seq / 1000, seq % 1000);

  ++seq;

  /* Make sure that SEQ's value fits in 5 digits if temp_dir is on
     an 8.3 filesystem.  */
  if (!long_file_names && seq >= 100000)
    seq = 0;

  node = (struct tempnode *) xmalloc (sizeof (struct tempnode));
  node->name = name;
  node->next = temphead.next;
  temphead.next = node;
  return name;
}

/* Search through the list of temporary files for NAME;
   remove it if it is found on the list. */

static void
zaptemp (const char *name)
{
  struct tempnode *node, *temp;

  for (node = &temphead; node->next; node = node->next)
    if (STREQ (name, node->next->name))
      break;
  if (node->next)
    {
      temp = node->next;
      unlink (temp->name);
      free (temp->name);
      node->next = temp->next;
      free ((char *) temp);
    }
}

#ifdef ENABLE_NLS

static int
struct_month_cmp (const void *m1, const void *m2)
{
  return strcmp (((const struct month *) m1)->name,
                 ((const struct month *) m2)->name);
}

#endif /* NLS */

/* Initialize the character class tables. */

static void
inittables (void)
{
  int i;

  for (i = 0; i < UCHAR_LIM; ++i)
    {
      if (ISBLANK (i))
        blanks[i] = 1;
      if (!ISPRINT (i))
        nonprinting[i] = 1;
      if (!ISALNUM (i) && !ISBLANK (i))
        nondictionary[i] = 1;
      if (ISLOWER (i))
        fold_toupper[i] = toupper (i);
      else
        fold_toupper[i] = i;
    }

#if defined ENABLE_NLS && HAVE_NL_LANGINFO
  /* If we're not in the "C" locale, read different names for months.  */
  if (hard_LC_TIME)
    {
      for (i = 0; i < MONTHS_PER_YEAR; i++)
        {
          char *s;
          size_t s_len;
          size_t j;
          char *name;

          s = (char *) nl_langinfo (ABMON_1 + i);
          s_len = strlen (s);
          monthtab[i].name = name = (char *) xmalloc (s_len + 1);
          monthtab[i].val = i + 1;

          for (j = 0; j < s_len; j++)
            name[j] = fold_toupper[UCHAR (s[j])];
          name[j] = '\0';
        }
      qsort ((void *) monthtab, MONTHS_PER_YEAR,
             sizeof (struct month), struct_month_cmp);
    }
#endif /* NLS */
}

/* Initialize BUF, allocating ALLOC bytes initially. */

static void
initbuf (struct buffer *buf, int alloc)
{
  buf->alloc = alloc;
  buf->buf = xmalloc (buf->alloc);
  buf->used = buf->left = 0;
}

/* Fill BUF reading from FP, moving buf->left bytes from the end
   of buf->buf to the beginning first.  If EOF is reached and the
   file wasn't terminated by a newline, supply one.  Return a count
   of bytes buffered. */

static int
fillbuf (struct buffer *buf, FILE *fp)
{
  int cc;

  memmove (buf->buf, buf->buf + buf->used - buf->left, buf->left);
  buf->used = buf->left;

  while (!feof (fp) && (buf->used == 0
                        || !memchr (buf->buf, eolchar, buf->used)))
    {
      if (buf->used == buf->alloc)
        {
          buf->alloc *= 2;
          buf->buf = xrealloc (buf->buf, buf->alloc);
        }
      cc = fread (buf->buf + buf->used, 1, buf->alloc - buf->used, fp);
      if (ferror (fp))
        {
          error (0, errno, _("read error"));
          cleanup ();
          exit (SORT_FAILURE);
        }
      buf->used += cc;
    }

  if (feof (fp) && buf->used && buf->buf[buf->used - 1] != eolchar)
    {
      if (buf->used == buf->alloc)
        {
          buf->alloc *= 2;
          buf->buf = xrealloc (buf->buf, buf->alloc);
        }
      buf->buf[buf->used++] = eolchar;
    }

  return buf->used;
}

/* Initialize LINES, allocating space for ALLOC lines initially.
   LIMIT is the maximum possible number of lines to allocate space
   for, ever.  */

static void
initlines (struct lines *lines, int alloc, int limit)
{
  lines->alloc = alloc;
  lines->lines = (struct line *) xmalloc (lines->alloc * sizeof (struct line));
  lines->used = 0;
  lines->limit = limit;
}

/* Return a pointer to the first character of the field specified
   by KEY in LINE. */

static char *
begfield (const struct line *line, const struct keyfield *key)
{
  register char *ptr = line->text, *lim = ptr + line->length - 1;
  register int sword = key->sword, schar = key->schar;

  if (tab)
    while (ptr < lim && sword--)
      {
        while (ptr < lim && *ptr != tab)
          ++ptr;
        if (ptr < lim)
          ++ptr;
      }
  else
    while (ptr < lim && sword--)
      {
        while (ptr < lim && blanks[UCHAR (*ptr)])
          ++ptr;
        while (ptr < lim && !blanks[UCHAR (*ptr)])
          ++ptr;
      }

  if (key->skipsblanks)
    while (ptr < lim && blanks[UCHAR (*ptr)])
      ++ptr;

  if (ptr + schar <= lim)
    ptr += schar;
  else
    ptr = lim;

  return ptr;
}

/* Return the limit of (a pointer to the first character after) the field
   in LINE specified by KEY. */

static char *
limfield (const struct line *line, const struct keyfield *key)
{
  register char *ptr = line->text, *lim = ptr + line->length - 1;
  register int eword = key->eword, echar = key->echar;

  /* Note: from the POSIX spec:
     The leading field separator itself is included in
     a field when -t is not used.  FIXME: move this comment up... */

  /* Move PTR past EWORD fields or to one past the last byte on LINE,
     whichever comes first.  If there are more than EWORD fields, leave
     PTR pointing at the beginning of the field having zero-based index,
     EWORD.  If a delimiter character was specified (via -t), then that
     `beginning' is the first character following the delimiting TAB.
     Otherwise, leave PTR pointing at the first `blank' character after
     the preceding field.  */
  if (tab)
    while (ptr < lim && eword--)
      {
        while (ptr < lim && *ptr != tab)
          ++ptr;
        if (ptr < lim && (eword || echar > 0))
          ++ptr;
      }
  else
    while (ptr < lim && eword--)
      {
        while (ptr < lim && blanks[UCHAR (*ptr)])
          ++ptr;
        while (ptr < lim && !blanks[UCHAR (*ptr)])
          ++ptr;
      }

#ifdef POSIX_UNSPECIFIED
  /* The following block of code makes GNU sort incompatible with
     standard Unix sort, so it's ifdef'd out for now.
     The POSIX spec isn't clear on how to interpret this.
     FIXME: request clarification.

     From: kwzh@gnu.ai.mit.edu (Karl Heuer)
     Date: Thu, 30 May 96 12:20:41 -0400

     [...]I believe I've found another bug in `sort'.

     $ cat /tmp/sort.in
     a b c 2 d
     pq rs 1 t
     $ textutils-1.15/src/sort +0.6 -0.7 </tmp/sort.in
     a b c 2 d
     pq rs 1 t
     $ /bin/sort +0.6 -0.7 </tmp/sort.in
     pq rs 1 t
     a b c 2 d

     Unix sort produced the answer I expected: sort on the single character
     in column 6.  GNU sort produced different results, because it disagrees
     on the interpretation of the key-end spec "-M.N".  Unix sort reads this
     as "skip M fields, then N characters"; but GNU sort wants it to mean
     "skip M fields, then either N characters or the rest of the current
     field, whichever comes first".  This extra clause applies only to
     key-ends, not key-starts.
     */

  /* Make LIM point to the end of (one byte past) the current field.  */
  if (tab)
    {
      char *newlim;
      newlim = memchr (ptr, tab, lim - ptr);
      if (newlim)
        lim = newlim;
    }
  else
    {
      char *newlim;
      newlim = ptr;
      while (newlim < lim && blanks[UCHAR (*newlim)])
        ++newlim;
      while (newlim < lim && !blanks[UCHAR (*newlim)])
        ++newlim;
      lim = newlim;
    }
#endif

  /* If we're skipping leading blanks, don't start counting characters
     until after skipping past any leading blanks.  */
  if (key->skipsblanks)
    while (ptr < lim && blanks[UCHAR (*ptr)])
      ++ptr;

  /* Advance PTR by ECHAR (if possible), but no further than LIM.  */
  if (ptr + echar <= lim)
    ptr += echar;
  else
    ptr = lim;

  return ptr;
}

/* FIXME */

void
trim_trailing_blanks (const char *a_start, char **a_end)
{
  while (*a_end > a_start && blanks[UCHAR (*(*a_end - 1))])
    --(*a_end);
}

/* Find the lines in BUF, storing pointers and lengths in LINES.  */

static void
findlines (struct buffer *buf, struct lines *lines)
{
  register char *beg = buf->buf, *lim = buf->buf + buf->used, *ptr;
  struct keyfield *key = keyhead.next;

  lines->used = 0;

  while (beg < lim && (ptr = memchr (beg, eolchar, lim - beg))
         && lines->used < lines->limit)
    {
      if (lines->used == lines->alloc)
        {
          lines->alloc *= 2;
          lines->lines = (struct line *)
            xrealloc ((char *) lines->lines,
                      lines->alloc * sizeof (struct line));
        }

      lines->lines[lines->used].text = beg;
      lines->lines[lines->used].length = ptr + 1 - beg;

      /* Precompute the position of the first key for efficiency. */
      if (key)
        {
          if (key->eword >= 0)
            lines->lines[lines->used].keylim =
              limfield (&lines->lines[lines->used], key);
          else
            lines->lines[lines->used].keylim = ptr;

          if (key->sword >= 0)
            lines->lines[lines->used].keybeg =
              begfield (&lines->lines[lines->used], key);
          else
            {
              if (key->skipsblanks)
                while (blanks[UCHAR (*beg)])
                  ++beg;
              lines->lines[lines->used].keybeg = beg;
            }
          if (key->skipeblanks)
            {
              trim_trailing_blanks (lines->lines[lines->used].keybeg,
                                    &lines->lines[lines->used].keylim);
            }
        }
      else
        {
          lines->lines[lines->used].keybeg = 0;
          lines->lines[lines->used].keylim = 0;
        }

      ++lines->used;
      beg = ptr + 1;
    }

  buf->left = lim - beg;
}

/* Compare strings A and B containing decimal fractions < 1.  Each string
   should begin with a decimal point followed immediately by the digits
   of the fraction.  Strings not of this form are considered to be zero. */

/* The goal here, is to take two numbers a and b... compare these
   in parallel.  Instead of converting each, and then comparing the
   outcome.  Most likely stopping the comparison before the conversion
   is complete.  The algorithm used, in the old sort:

   Algorithm: fraccompare
   Action   : compare two decimal fractions
   accepts  : char *a, char *b
   returns  : -1 if a<b, 0 if a=b, 1 if a>b.
   implement:

   if *a == decimal_point AND *b == decimal_point
     find first character different in a and b.
     if both are digits, return the difference *a - *b.
     if *a is a digit
       skip past zeros
       if digit return 1, else 0
     if *b is a digit
       skip past zeros
       if digit return -1, else 0
   if *a is a decimal_point
     skip past decimal_point and zeros
     if digit return 1, else 0
   if *b is a decimal_point
     skip past decimal_point and zeros
     if digit return -1, else 0
   return 0 */

static int
fraccompare (register const char *a, register const char *b)
{
  if (*a == decimal_point && *b == decimal_point)
    {
      while (*++a == *++b)
        if (! ISDIGIT (*a))
          return 0;
      if (ISDIGIT (*a) && ISDIGIT (*b))
        return *a - *b;
      if (ISDIGIT (*a))
        goto a_trailing_nonzero;
      if (ISDIGIT (*b))
        goto b_trailing_nonzero;
      return 0;
    }
  else if (*a++ == decimal_point)
    {
    a_trailing_nonzero:
      while (*a == NUMERIC_ZERO)
        a++;
      return ISDIGIT (*a);
    }
  else if (*b++ == decimal_point)
    {
    b_trailing_nonzero:
      while (*b == NUMERIC_ZERO)
        b++;
      return - ISDIGIT (*b);
    }
  return 0;
}

/* Compare strings A and B as numbers without explicitly converting them to
   machine numbers.  Comparatively slow for short strings, but asymptotically
   hideously fast. */

static int
numcompare (register const char *a, register const char *b)
{
  register int tmpa, tmpb, loga, logb, tmp;

  tmpa = *a;
  tmpb = *b;

  while (blanks[UCHAR (tmpa)])
    tmpa = *++a;
  while (blanks[UCHAR (tmpb)])
    tmpb = *++b;

  if (tmpa == NEGATION_SIGN)
    {
      do
        tmpa = *++a;
      while (tmpa == NUMERIC_ZERO || IS_THOUSANDS_SEP (tmpa));
      if (tmpb != NEGATION_SIGN)
        {
          if (tmpa == decimal_point)
            do
              tmpa = *++a;
            while (tmpa == NUMERIC_ZERO);
          if (ISDIGIT (tmpa))
            return -1;
          while (tmpb == NUMERIC_ZERO || IS_THOUSANDS_SEP (tmpb))
            tmpb = *++b;
          if (tmpb == decimal_point)
            do
              tmpb = *++b;
            while (tmpb == NUMERIC_ZERO);
          if (ISDIGIT (tmpb))
            return -1;
          return 0;
        }
      do
        tmpb = *++b;
      while (tmpb == NUMERIC_ZERO || IS_THOUSANDS_SEP (tmpb));

      while (tmpa == tmpb && ISDIGIT (tmpa))
        {
          do
            tmpa = *++a;
          while (IS_THOUSANDS_SEP (tmpa));
          do
            tmpb = *++b;
          while (IS_THOUSANDS_SEP (tmpb));
        }

      if ((tmpa == decimal_point && !ISDIGIT (tmpb))
          || (tmpb == decimal_point && !ISDIGIT (tmpa)))
        return -fraccompare (a, b);

      tmp = tmpb - tmpa;

      for (loga = 0; ISDIGIT (tmpa); ++loga)
        do
          tmpa = *++a;
        while (IS_THOUSANDS_SEP (tmpa));

      for (logb = 0; ISDIGIT (tmpb); ++logb)
        do
          tmpb = *++b;
        while (IS_THOUSANDS_SEP (tmpb));

      if (logb - loga != 0)
        return logb - loga;

      if (!loga)
        return 0;

      return tmp;
    }
  else if (tmpb == NEGATION_SIGN)
    {
      do
        tmpb = *++b;
      while (tmpb == NUMERIC_ZERO || IS_THOUSANDS_SEP (tmpb));
      if (tmpb == decimal_point)
        do
          tmpb = *++b;
        while (tmpb == NUMERIC_ZERO);
      if (ISDIGIT (tmpb))
        return 1;
      while (tmpa == NUMERIC_ZERO || IS_THOUSANDS_SEP (tmpa))
        tmpa = *++a;
      if (tmpa == decimal_point)
        do
          tmpa = *++a;
        while (tmpa == NUMERIC_ZERO);
      if (ISDIGIT (tmpa))
        return 1;
      return 0;
    }
  else
    {
      while (tmpa == NUMERIC_ZERO || IS_THOUSANDS_SEP (tmpa))
        tmpa = *++a;
      while (tmpb == NUMERIC_ZERO || IS_THOUSANDS_SEP (tmpb))
        tmpb = *++b;

      while (tmpa == tmpb && ISDIGIT (tmpa))
        {
          do
            tmpa = *++a;
          while (IS_THOUSANDS_SEP (tmpa));
          do
            tmpb = *++b;
          while (IS_THOUSANDS_SEP (tmpb));
        }

      if ((tmpa == decimal_point && !ISDIGIT (tmpb))
          || (tmpb == decimal_point && !ISDIGIT (tmpa)))
        return fraccompare (a, b);

      tmp = tmpa - tmpb;

      for (loga = 0; ISDIGIT (tmpa); ++loga)
        do
          tmpa = *++a;
        while (IS_THOUSANDS_SEP (tmpa));

      for (logb = 0; ISDIGIT (tmpb); ++logb)
        do
          tmpb = *++b;
        while (IS_THOUSANDS_SEP (tmpb));

      if (loga - logb != 0)
        return loga - logb;

      if (!loga)
        return 0;

      return tmp;
    }
}

static int
general_numcompare (const char *sa, const char *sb)
{
  /* FIXME: add option to warn about failed conversions.  */
  /* FIXME: maybe add option to try expensive FP conversion
     only if A and B can't be compared more cheaply/accurately.  */

  char *ea;
  char *eb;
  double a = strtod (sa, &ea);
  double b = strtod (sb, &eb);

  /* Put conversion errors at the start of the collating sequence.  */
  if (sa == ea)
    return sb == eb ? 0 : -1;
  if (sb == eb)
    return 1;

  /* Sort numbers in the usual way, where -0 == +0.  Put NaNs after
     conversion errors but before numbers; sort them by internal
     bit-pattern, for lack of a more portable alternative.  */
  return (a < b ? -1
          : a > b ? 1
          : a == b ? 0
          : b == b ? -1
          : a == a ? 1
          : memcmp ((char *) &a, (char *) &b, sizeof a));
}

/* Return an integer in 1..12 of the month name S with length LEN.
   Return 0 if the name in S is not recognized.  */

static int
getmonth (const char *s, int len)
{
  char *month;
  register int i, lo = 0, hi = MONTHS_PER_YEAR, result;

  while (len > 0 && blanks[UCHAR (*s)])
    {
      ++s;
      --len;
    }

  if (len == 0)
    return 0;

  month = (char *) alloca (len + 1);
  for (i = 0; i < len; ++i)
    month[i] = fold_toupper[UCHAR (s[i])];
  while (blanks[UCHAR (month[i - 1])])
    --i;
  month[i] = '\0';

  do
    {
      int ix = (lo + hi) / 2;

      if (strncmp (month, monthtab[ix].name, strlen (monthtab[ix].name)) < 0)
        hi = ix;
      else
        lo = ix;
    }
  while (hi - lo > 1);

  result = (!strncmp (month, monthtab[lo].name, strlen (monthtab[lo].name))
            ? monthtab[lo].val : 0);

  return result;
}

/* Compare two lines A and B trying every key in sequence until there
   are no more keys or a difference is found. */

static int
keycompare (const struct line *a, const struct line *b)
{
  register char *texta, *textb, *lima, *limb;
  register unsigned char *translate;
  register int *ignore;
  struct keyfield *key;
  int diff = 0, iter = 0, lena, lenb;

  for (key = keyhead.next; key; key = key->next, ++iter)
    {
      int comparable_lengths = 1;

      ignore = key->ignore;
      translate = (unsigned char *) key->translate;

      /* Find the beginning and limit of each field. */
      if (iter || a->keybeg == NULL || b->keybeg == NULL)
        {
          if (key->eword >= 0)
            lima = limfield (a, key), limb = limfield (b, key);
          else
            lima = a->text + a->length - 1, limb = b->text + b->length - 1;

          if (key->sword >= 0)
            texta = begfield (a, key), textb = begfield (b, key);
          else
            {
              texta = a->text, textb = b->text;
              if (key->skipsblanks)
                {
                  while (texta < lima && blanks[UCHAR (*texta)])
                    ++texta;
                  while (textb < limb && blanks[UCHAR (*textb)])
                    ++textb;
                }
            }
        }
      else
        {
          /* For the first iteration only, the key positions have
             been precomputed for us. */
          texta = a->keybeg, lima = a->keylim;
          textb = b->keybeg, limb = b->keylim;
        }

      /* Find the lengths. */
      lena = lima - texta, lenb = limb - textb;
      if (lena < 0)
        lena = 0;
      if (lenb < 0)
        lenb = 0;

      if (key->skipeblanks)
        {
          char *a_end = texta + lena;
          char *b_end = textb + lenb;
          trim_trailing_blanks (texta, &a_end);
          trim_trailing_blanks (textb, &b_end);
          lena = a_end - texta;
          lenb = b_end - textb;
        }

      /* Actually compare the fields. */
      if (key->numeric | key->general_numeric)
        {
          char savea = *lima, saveb = *limb;

          *lima = *limb = '\0';
          diff = ((key->numeric ? numcompare : general_numcompare)
                  (texta, textb));
          *lima = savea, *limb = saveb;
          if (diff)
            return key->reverse ? -diff : diff;
          continue;
        }
      else if (key->month)
        {
          diff = getmonth (texta, lena) - getmonth (textb, lenb);
          if (diff)
            return key->reverse ? -diff : diff;
          continue;
        }
#ifdef ENABLE_NLS

      /* Sorting like this may become slow, so in a simple locale the user
         can select a faster sort that is similar to ascii sort  */
      else if (hard_LC_COLLATE | hard_LC_CTYPE)
        {
          if (ignore || translate)
            {
              char *copy_a = (char *) alloca (lena + 1);
              char *copy_b = (char *) alloca (lenb + 1);
              int new_len_a, new_len_b, i;

              /* Ignore and/or translate chars before comparing.  */
              for (new_len_a = new_len_b = i = 0; i < max (lena, lenb); i++)
                {
                  if (i < lena)
                    {
                      copy_a[new_len_a] = (translate
                                           ? translate[UCHAR (texta[i])]
                                           : texta[i]);
                      if (!ignore || !ignore[UCHAR (texta[i])])
                        ++new_len_a;
                    }
                  if (i < lenb)
                    {
                      copy_b[new_len_b] = (translate
                                           ? translate[UCHAR (textb[i])]
                                           : textb [i]);
                      if (!ignore || !ignore[UCHAR (textb[i])])
                        ++new_len_b;
                    }
                }

              diff = memcoll (copy_a, new_len_a, copy_b, new_len_b);
            }
          else
            {
              diff = memcoll (texta, lena, textb, lenb);
            }

          if (diff)
            return key->reverse ? -diff : diff;

          continue;
        }
#endif
      else if (ignore && translate)

#define CMP_WITH_IGNORE(A, B)                                           \
  do                                                                    \
    {                                                                   \
          while (texta < lima && textb < limb)                          \
            {                                                           \
              while (texta < lima && ignore[UCHAR (*texta)])            \
                ++texta;                                                \
              while (textb < limb && ignore[UCHAR (*textb)])            \
                ++textb;                                                \
              if (texta < lima && textb < limb)                         \
                {                                                       \
                  if ((A) != (B))                                       \
                    {                                                   \
                      diff = UCHAR (A) - UCHAR (B);                     \
                      break;                                            \
                    }                                                   \
                  ++texta;                                              \
                  ++textb;                                              \
                }                                                       \
                                                                        \
              if (texta == lima && textb < limb && !ignore[UCHAR (*textb)]) \
                diff = -1;                                              \
              else if (texta < lima && textb == limb                    \
                       && !ignore[UCHAR (*texta)])                      \
                diff = 1;                                               \
            }                                                           \
                                                                        \
          if (diff == 0)                                                \
            {                                                           \
              while (texta < lima && ignore[UCHAR (*texta)])            \
                ++texta;                                                \
              while (textb < limb && ignore[UCHAR (*textb)])            \
                ++textb;                                                \
                                                                        \
              if (texta == lima && textb < limb)                        \
                diff = -1;                                              \
              else if (texta < lima && textb == limb)                   \
                diff = 1;                                               \
            }                                                           \
          /* Relative lengths are meaningless if characters were ignored.  \
             Handling this case here avoids what might be an invalid length  \
             comparison below.  */                                      \
          if (diff == 0 && texta == lima && textb == limb)              \
            comparable_lengths = 0;                                     \
    }                                                                   \
  while (0)

        CMP_WITH_IGNORE (translate[UCHAR (*texta)], translate[UCHAR (*textb)]);
      else if (ignore)
        CMP_WITH_IGNORE (UCHAR (*texta), UCHAR (*textb));
      else if (translate)
        while (texta < lima && textb < limb)
          {
            if (translate[UCHAR (*texta++)] != translate[UCHAR (*textb++)])
              {
                diff = (UCHAR (translate[UCHAR (*--texta)])
                        - UCHAR (translate[UCHAR (*--textb)]));
                break;
              }
          }
      else
        {
#ifdef ENABLE_NLS
          if (hard_LC_COLLATE)
            {
              /* Ignore any length difference if the localized comparison
                 says the strings are equal.  */
              comparable_lengths = 0;
              diff = memcoll (texta, lena, textb, lenb);
            }
          else
#endif
            {
              diff = memcmp (texta, textb, min (lena, lenb));
            }
        }

      if (diff)
        return key->reverse ? -diff : diff;
      if (comparable_lengths && (diff = lena - lenb) != 0)
        return key->reverse ? -diff : diff;
    }

  return 0;
}

/* Compare two lines A and B, returning negative, zero, or positive
   depending on whether A compares less than, equal to, or greater than B. */

static int
compare (register const struct line *a, register const struct line *b)
{
  int diff, alen, blen, minlen;

  /* First try to compare on the specified keys (if any).
     The only two cases with no key at all are unadorned sort,
     and unadorned sort -r. */
  if (keyhead.next)
    {
      diff = keycompare (a, b);
      if (diff != 0 || unique || stable)
        {
          alloca (0);
          return diff;
        }
    }

  /* If the keys all compare equal (or no keys were specified)
     fall through to the default byte-by-byte comparison. */
  alen = a->length - 1, blen = b->length - 1;

#ifdef ENABLE_NLS
  if (hard_LC_COLLATE)
    {
      diff = memcoll (a->text, alen, b->text, blen);
      alloca (0);
      return reverse ? -diff : diff;
    }
#endif

  minlen = min (alen, blen);
  if (minlen == 0
      || (! (diff = UCHAR (a->text[0]) - UCHAR (b->text[0]))
          && ! (diff = memcmp (a->text, b->text, minlen))))
    diff = alen - blen;

  return reverse ? -diff : diff;
}

/* Check that the lines read from the given FP come in order.  Print a
   diagnostic (FILE_NAME, line number, contents of line) to stderr and return
   the line number of the first out-of-order line (counting from 1) if they
   are not in order.  Otherwise, print no diagnostic and return zero.  */

static int
checkfp (FILE *fp, const char *file_name)
{
  struct buffer buf;            /* Input buffer. */
  struct lines lines;           /* Lines scanned from the buffer. */
  struct line temp;             /* Copy of previous line. */
  int cc;                       /* Character count. */
  int alloc;
  int line_number = 1;
  struct line *disorder_line IF_LINT (= NULL);
  int disorder_line_number = 0;

  initbuf (&buf, mergealloc);
  initlines (&lines, mergealloc / linelength + 1,
             LINEALLOC / ((NMERGE + NMERGE) * sizeof (struct line)));
  alloc = linelength;
  temp.text = xmalloc (alloc);

  cc = fillbuf (&buf, fp);
  if (cc == 0)
    goto finish;

  findlines (&buf, &lines);

  while (1)
    {
      struct line *prev_line;   /* Pointer to previous line. */
      int cmp;                  /* Result of calling compare. */
      int i;

      /* Compare each line in the buffer with its successor. */
      for (i = 0; i < lines.used - 1; ++i)
        {
          cmp = compare (&lines.lines[i], &lines.lines[i + 1]);
          if ((unique && cmp >= 0) || (cmp > 0))
            {
              disorder_line = &lines.lines[i + 1];
              disorder_line_number = line_number + i + 1;
              goto finish;
            }
        }

      line_number += lines.used;

      /* Save the last line of the buffer and refill the buffer. */
      prev_line = lines.lines + (lines.used - 1);
      if (alloc < prev_line->length)
        {
          do
            {
              alloc *= 2;
            }
          while (alloc < prev_line->length);
          temp.text = xrealloc (temp.text, alloc);
        }
      assert (prev_line->length <= alloc);
      memcpy (temp.text, prev_line->text, prev_line->length);
      temp.length = prev_line->length;
      temp.keybeg = temp.text + (prev_line->keybeg - prev_line->text);
      temp.keylim = temp.text + (prev_line->keylim - prev_line->text);

      cc = fillbuf (&buf, fp);
      if (cc == 0)
        break;

      findlines (&buf, &lines);
      /* Make sure the line saved from the old buffer contents is
         less than or equal to the first line of the new buffer. */
      cmp = compare (&temp, &lines.lines[0]);
      if ((unique && cmp >= 0) || (cmp > 0))
        {
          disorder_line = &lines.lines[0];
          disorder_line_number = line_number;
          break;
        }
    }

finish:
  xfclose (fp);

  if (disorder_line_number)
    {
      fprintf (stderr, _("%s: %s:%d: disorder: "), program_name, file_name,
               disorder_line_number);
      write_bytes (disorder_line->text, disorder_line->length, stderr,
                   _("standard error"));
    }

  free (buf.buf);
  free ((char *) lines.lines);
  free (temp.text);
  return disorder_line_number;
}

/* Merge lines from FPS onto OFP.  NFPS cannot be greater than NMERGE.
   Close FPS before returning. */

static void
mergefps (FILE **fps, register int nfps, FILE *ofp, const char *output_file)
{
  struct buffer buffer[NMERGE]; /* Input buffers for each file. */
  struct lines lines[NMERGE];   /* Line tables for each buffer. */
  struct line saved;            /* Saved line for unique check. */
  int savedflag = 0;            /* True if there is a saved line. */
  int savealloc IF_LINT (= 0);  /* Size allocated for the saved line. */
  int cur[NMERGE];              /* Current line in each line table. */
  int ord[NMERGE];              /* Table representing a permutation of fps,
                                   such that lines[ord[0]].lines[cur[ord[0]]]
                                   is the smallest line and will be next
                                   output. */
  register int i, j, t;

  /* Allocate space for a saved line if necessary. */
  if (unique)
    {
      savealloc = linelength;
      saved.text = xmalloc (savealloc);
    }

  /* Read initial lines from each input file. */
  for (i = 0; i < nfps; ++i)
    {
      initbuf (&buffer[i], mergealloc);
      /* If a file is empty, eliminate it from future consideration. */
      while (i < nfps && !fillbuf (&buffer[i], fps[i]))
        {
          xfclose (fps[i]);
          --nfps;
          for (j = i; j < nfps; ++j)
            fps[j] = fps[j + 1];
        }
      if (i == nfps)
        free (buffer[i].buf);
      else
        {
          initlines (&lines[i], mergealloc / linelength + 1,
                     LINEALLOC / ((NMERGE + NMERGE) * sizeof (struct line)));
          findlines (&buffer[i], &lines[i]);
          cur[i] = 0;
        }
    }

  /* Set up the ord table according to comparisons among input lines.
     Since this only reorders two items if one is strictly greater than
     the other, it is stable. */
  for (i = 0; i < nfps; ++i)
    ord[i] = i;
  for (i = 1; i < nfps; ++i)
    if (compare (&lines[ord[i - 1]].lines[cur[ord[i - 1]]],
                 &lines[ord[i]].lines[cur[ord[i]]]) > 0)
      t = ord[i - 1], ord[i - 1] = ord[i], ord[i] = t, i = 0;

  /* Repeatedly output the smallest line until no input remains. */
  while (nfps)
    {
      /* If uniquified output is turned on, output only the first of
         an identical series of lines. */
      if (unique)
        {
          if (savedflag && compare (&saved, &lines[ord[0]].lines[cur[ord[0]]]))
            {
              write_bytes (saved.text, saved.length, ofp, output_file);
              savedflag = 0;
            }
          if (!savedflag)
            {
              if (savealloc < lines[ord[0]].lines[cur[ord[0]]].length)
                {
                  while (savealloc < lines[ord[0]].lines[cur[ord[0]]].length)
                    savealloc *= 2;
                  saved.text = xrealloc (saved.text, savealloc);
                }
              saved.length = lines[ord[0]].lines[cur[ord[0]]].length;
              memcpy (saved.text, lines[ord[0]].lines[cur[ord[0]]].text,
                      saved.length);
              if (lines[ord[0]].lines[cur[ord[0]]].keybeg != NULL)
                {
                  saved.keybeg = saved.text +
                    (lines[ord[0]].lines[cur[ord[0]]].keybeg
                     - lines[ord[0]].lines[cur[ord[0]]].text);
                }
              if (lines[ord[0]].lines[cur[ord[0]]].keylim != NULL)
                {
                  saved.keylim = saved.text +
                    (lines[ord[0]].lines[cur[ord[0]]].keylim
                     - lines[ord[0]].lines[cur[ord[0]]].text);
                }
              savedflag = 1;
            }
        }
      else
        write_bytes (lines[ord[0]].lines[cur[ord[0]]].text,
                     lines[ord[0]].lines[cur[ord[0]]].length, ofp, output_file);

      /* Check if we need to read more lines into core. */
      if (++cur[ord[0]] == lines[ord[0]].used)
        {
          if (fillbuf (&buffer[ord[0]], fps[ord[0]]))
            {
              findlines (&buffer[ord[0]], &lines[ord[0]]);
              cur[ord[0]] = 0;
            }
          else
            {
              /* We reached EOF on fps[ord[0]]. */
              for (i = 1; i < nfps; ++i)
                if (ord[i] > ord[0])
                  --ord[i];
              --nfps;
              xfclose (fps[ord[0]]);
              free (buffer[ord[0]].buf);
              free ((char *) lines[ord[0]].lines);
              for (i = ord[0]; i < nfps; ++i)
                {
                  fps[i] = fps[i + 1];
                  buffer[i] = buffer[i + 1];
                  lines[i] = lines[i + 1];
                  cur[i] = cur[i + 1];
                }
              for (i = 0; i < nfps; ++i)
                ord[i] = ord[i + 1];
              continue;
            }
        }

      /* The new line just read in may be larger than other lines
         already in core; push it back in the queue until we encounter
         a line larger than it. */
      for (i = 1; i < nfps; ++i)
        {
          t = compare (&lines[ord[0]].lines[cur[ord[0]]],
                       &lines[ord[i]].lines[cur[ord[i]]]);
          if (!t)
            t = ord[0] - ord[i];
          if (t < 0)
            break;
        }
      t = ord[0];
      for (j = 1; j < i; ++j)
        ord[j - 1] = ord[j];
      ord[i - 1] = t;
    }

  if (unique && savedflag)
    {
      write_bytes (saved.text, saved.length, ofp, output_file);
      free (saved.text);
    }
}

/* Sort the array LINES with NLINES members, using TEMP for temporary space. */

static void
sortlines (struct line *lines, int nlines, struct line *temp)
{
  register struct line *lo, *hi, *t;
  register int nlo, nhi;

  if (nlines == 2)
    {
      if (compare (&lines[0], &lines[1]) > 0)
        {
          *temp = lines[0];
          lines[0] = lines[1];
          lines[1] = *temp;
        }
      return;
    }

  nlo = nlines / 2;
  lo = lines;
  nhi = nlines - nlo;
  hi = lines + nlo;

  if (nlo > 1)
    sortlines (lo, nlo, temp);

  if (nhi > 1)
    sortlines (hi, nhi, temp);

  t = temp;

  while (nlo && nhi)
    if (compare (lo, hi) <= 0)
      *t++ = *lo++, --nlo;
    else
      *t++ = *hi++, --nhi;
  while (nlo--)
    *t++ = *lo++;

  for (lo = lines, nlo = nlines - nhi, t = temp; nlo; --nlo)
    *lo++ = *t++;
}

/* Check that each of the NFILES FILES is ordered.
   Return a count of disordered files. */

static int
check (char **files, int nfiles)
{
  int i, disorders = 0;
  FILE *fp;

  for (i = 0; i < nfiles; ++i)
    {
      fp = xfopen (files[i], "r");
      if (checkfp (fp, files[i]))
        {
          ++disorders;
        }
    }
  return disorders;
}

/* Merge NFILES FILES onto OFP. */

static void
merge (char **files, int nfiles, FILE *ofp, const char *output_file)
{
  int i, j, t;
  char *temp;
  FILE *fps[NMERGE], *tfp;

  while (nfiles > NMERGE)
    {
      t = 0;
      for (i = 0; i < nfiles / NMERGE; ++i)
        {
          for (j = 0; j < NMERGE; ++j)
            fps[j] = xfopen (files[i * NMERGE + j], "r");
          tfp = xtmpfopen (temp = tempname ());
          mergefps (fps, NMERGE, tfp, temp);
          xfclose (tfp);
          for (j = 0; j < NMERGE; ++j)
            zaptemp (files[i * NMERGE + j]);
          files[t++] = temp;
        }
      for (j = 0; j < nfiles % NMERGE; ++j)
        fps[j] = xfopen (files[i * NMERGE + j], "r");
      tfp = xtmpfopen (temp = tempname ());
      mergefps (fps, nfiles % NMERGE, tfp, temp);
      xfclose (tfp);
      for (j = 0; j < nfiles % NMERGE; ++j)
        zaptemp (files[i * NMERGE + j]);
      files[t++] = temp;
      nfiles = t;
    }

  for (i = 0; i < nfiles; ++i)
    fps[i] = xfopen (files[i], "r");
  mergefps (fps, i, ofp, output_file);
  for (i = 0; i < nfiles; ++i)
    zaptemp (files[i]);
}

/* Sort NFILES FILES onto OFP. */

static void
sort (char **files, int nfiles, FILE *ofp, const char *output_file)
{
  struct buffer buf;
  struct lines lines;
  struct line *tmp;
  int i, ntmp;
  FILE *fp, *tfp;
  struct tempnode *node;
  int n_temp_files = 0;
  char **tempfiles;

  initbuf (&buf, sortalloc);
  initlines (&lines, sortalloc / linelength + 1,
             LINEALLOC / sizeof (struct line));
  ntmp = lines.alloc;
  tmp = (struct line *) xmalloc (ntmp * sizeof (struct line));

  while (nfiles--)
    {
      const char *temp_output;

      fp = xfopen (*files++, "r");
      while (fillbuf (&buf, fp))
        {
          findlines (&buf, &lines);
          if (lines.used > ntmp)
            {
              while (lines.used > ntmp)
                ntmp *= 2;
              tmp = (struct line *)
                xrealloc ((char *) tmp, ntmp * sizeof (struct line));
            }
          sortlines (lines.lines, lines.used, tmp);
          if (feof (fp) && !nfiles && !n_temp_files && !buf.left)
            {
              tfp = ofp;
              temp_output = output_file;
            }
          else
            {
              ++n_temp_files;
              tfp = xtmpfopen (temp_output = tempname ());
            }
          for (i = 0; i < lines.used; ++i)
            if (!unique || i == 0
                || compare (&lines.lines[i], &lines.lines[i - 1]))
              write_bytes (lines.lines[i].text, lines.lines[i].length, tfp,
                           temp_output);
          if (tfp != ofp)
            xfclose (tfp);
        }
      xfclose (fp);
    }

  free (buf.buf);
  free ((char *) lines.lines);
  free ((char *) tmp);

  if (n_temp_files)
    {
      tempfiles = (char **) xmalloc (n_temp_files * sizeof (char *));
      i = n_temp_files;
      for (node = temphead.next; i > 0; node = node->next)
        tempfiles[--i] = node->name;
      merge (tempfiles, n_temp_files, ofp, output_file);
      free ((char *) tempfiles);
    }
}

/* Insert key KEY at the end of the list (`keyhead'). */

static void
insertkey (struct keyfield *key)
{
  struct keyfield *k = &keyhead;

  while (k->next)
    k = k->next;
  k->next = key;
  key->next = NULL;
}

static void
badfieldspec (const char *s)
{
  error (SORT_FAILURE, 0, _("invalid field specification `%s'"), s);
}

/* Handle interrupts and hangups. */

static void
sighandler (int sig)
{
#ifdef SA_INTERRUPT
  struct sigaction sigact;

  sigact.sa_handler = SIG_DFL;
  sigemptyset (&sigact.sa_mask);
  sigact.sa_flags = 0;
  sigaction (sig, &sigact, NULL);
#else                           /* !SA_INTERRUPT */
  signal (sig, SIG_DFL);
#endif                          /* SA_INTERRUPT */
  cleanup ();
  kill (getpid (), sig);
}

/* Set the ordering options for KEY specified in S.
   Return the address of the first character in S that
   is not a valid ordering option.
   BLANKTYPE is the kind of blanks that 'b' should skip. */

static char *
set_ordering (register const char *s, struct keyfield *key,
              enum blanktype blanktype)
{
  while (*s)
    {
      switch (*s)
        {
        case 'b':
          if (blanktype == bl_start || blanktype == bl_both)
            key->skipsblanks = 1;
          if (blanktype == bl_end || blanktype == bl_both)
            key->skipeblanks = 1;
          break;
        case 'd':
          key->ignore = nondictionary;
          break;
        case 'f':
          key->translate = fold_toupper;
          break;
        case 'g':
          key->general_numeric = 1;
          break;
        case 'i':
          key->ignore = nonprinting;
          break;
        case 'M':
          key->month = 1;
          break;
        case 'n':
          key->numeric = 1;
          break;
        case 'r':
          key->reverse = 1;
          break;
        default:
          return (char *) s;
        }
      ++s;
    }
  return (char *) s;
}

static void
key_init (struct keyfield *key)
{
  memset (key, 0, sizeof (*key));
  key->eword = -1;
}

int
main (int argc, char **argv)
{
  struct keyfield *key = NULL, gkey;
  char *s;
  int i, t, t2;
  int checkonly = 0, mergeonly = 0, nfiles = 0;
  char *minus = "-", *outfile = minus, **files, *tmp;
  FILE *ofp;
#ifdef SA_INTERRUPT
  struct sigaction oldact, newact;
#endif                          /* SA_INTERRUPT */

  program_name = argv[0];
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

#ifdef ENABLE_NLS

  hard_LC_COLLATE = hard_locale (LC_COLLATE);
  hard_LC_CTYPE = hard_locale (LC_CTYPE);
# if HAVE_NL_LANGINFO
  hard_LC_TIME = hard_locale (LC_TIME);
# endif

  /* Let's get locale's representation of the decimal point */
  {
    struct lconv *lconvp = localeconv ();

    /* If the locale doesn't define a decimal point, or if the decimal
       point is multibyte, use the C decimal point.  We don't support
       multibyte decimal points yet.  */
    decimal_point = *lconvp->decimal_point;
    if (! decimal_point || lconvp->decimal_point[1])
      decimal_point = C_DECIMAL_POINT;

    /* We don't support multibyte thousands separators yet.  */
    th_sep = *lconvp->thousands_sep;
    if (! th_sep || lconvp->thousands_sep[1])
      th_sep = CHAR_MAX + 1;
  }

#endif /* NLS */

  parse_long_options (argc, argv, PROGRAM_NAME, GNU_PACKAGE, VERSION,
                      AUTHORS, usage);

  have_read_stdin = 0;
  inittables ();

  temp_dir = getenv ("TMPDIR");
  if (temp_dir == NULL)
    temp_dir = DEFAULT_TMPDIR;

  /* Change the way xmalloc and xrealloc fail.  */
  xalloc_exit_failure = SORT_FAILURE;
  xalloc_fail_func = cleanup;

#ifdef SA_INTERRUPT
  newact.sa_handler = sighandler;
  sigemptyset (&newact.sa_mask);
  newact.sa_flags = 0;

  sigaction (SIGINT, NULL, &oldact);
  if (oldact.sa_handler != SIG_IGN)
    sigaction (SIGINT, &newact, NULL);
  sigaction (SIGHUP, NULL, &oldact);
  if (oldact.sa_handler != SIG_IGN)
    sigaction (SIGHUP, &newact, NULL);
  sigaction (SIGPIPE, NULL, &oldact);
  if (oldact.sa_handler != SIG_IGN)
    sigaction (SIGPIPE, &newact, NULL);
  sigaction (SIGTERM, NULL, &oldact);
  if (oldact.sa_handler != SIG_IGN)
    sigaction (SIGTERM, &newact, NULL);
#else                           /* !SA_INTERRUPT */
  if (signal (SIGINT, SIG_IGN) != SIG_IGN)
    signal (SIGINT, sighandler);
  if (signal (SIGHUP, SIG_IGN) != SIG_IGN)
    signal (SIGHUP, sighandler);
  if (signal (SIGPIPE, SIG_IGN) != SIG_IGN)
    signal (SIGPIPE, sighandler);
  if (signal (SIGTERM, SIG_IGN) != SIG_IGN)
    signal (SIGTERM, sighandler);
#endif                          /* !SA_INTERRUPT */

  gkey.sword = gkey.eword = -1;
  gkey.ignore = NULL;
  gkey.translate = NULL;
  gkey.numeric = gkey.general_numeric = gkey.month = gkey.reverse = 0;
  gkey.skipsblanks = gkey.skipeblanks = 0;

  files = (char **) xmalloc (sizeof (char *) * argc);

  for (i = 1; i < argc; ++i)
    {
      if (argv[i][0] == '+')
        {
          if (key)
            insertkey (key);
          key = (struct keyfield *) xmalloc (sizeof (struct keyfield));
          key_init (key);
          s = argv[i] + 1;
          if (! (ISDIGIT (*s) || (*s == '.' && ISDIGIT (s[1]))))
            badfieldspec (argv[i]);
          for (t = 0; ISDIGIT (*s); ++s)
            t = 10 * t + *s - '0';
          t2 = 0;
          if (*s == '.')
            for (++s; ISDIGIT (*s); ++s)
              t2 = 10 * t2 + *s - '0';
          if (t2 || t)
            {
              key->sword = t;
              key->schar = t2;
            }
          else
            key->sword = -1;
          s = set_ordering (s, key, bl_start);
          if (*s)
            badfieldspec (argv[i]);
        }
      else if (argv[i][0] == '-' && argv[i][1])
        {
          s = argv[i] + 1;
          if (ISDIGIT (*s) || (*s == '.' && ISDIGIT (s[1])))
            {
              if (!key)
                {
                  /* Provoke with `sort -9'.  */
                  error (0, 0, _("when using the old-style +POS and -POS \
key specifiers,\nthe +POS specifier must come first"));
                  usage (SORT_FAILURE);
                }
              for (t = 0; ISDIGIT (*s); ++s)
                t = t * 10 + *s - '0';
              t2 = 0;
              if (*s == '.')
                for (++s; ISDIGIT (*s); ++s)
                  t2 = t2 * 10 + *s - '0';
              key->eword = t;
              key->echar = t2;
              s = set_ordering (s, key, bl_end);
              if (*s)
                badfieldspec (argv[i]);
              insertkey (key);
              key = NULL;
            }
          else
            while (*s)
              {
                s = set_ordering (s, &gkey, bl_both);
                switch (*s)
                  {
                  case '\0':
                    break;
                  case 'c':
                    checkonly = 1;
                    break;
                  case 'k':
                    if (s[1])
                      ++s;
                    else
                      {
                        if (i == argc - 1)
                          error (SORT_FAILURE, 0,
                                 _("option `-k' requires an argument"));
                        else
                          s = argv[++i];
                      }
                    if (key)
                      insertkey (key);
                    key = (struct keyfield *)
                      xmalloc (sizeof (struct keyfield));
                    key_init (key);
                    /* Get POS1. */
                    if (!ISDIGIT (*s))
                      badfieldspec (argv[i]);
                    for (t = 0; ISDIGIT (*s); ++s)
                      t = 10 * t + *s - '0';
                    if (t == 0)
                      {
                        /* Provoke with `sort -k0' */
                        error (0, 0, _("the starting field number argument \
to the `-k' option must be positive"));
                        badfieldspec (argv[i]);
                      }
                    --t;
                    t2 = 0;
                    if (*s == '.')
                      {
                        if (!ISDIGIT (s[1]))
                          {
                            /* Provoke with `sort -k1.' */
                            error (0, 0, _("starting field spec has `.' but \
lacks following character offset"));
                            badfieldspec (argv[i]);
                          }
                        for (++s; ISDIGIT (*s); ++s)
                          t2 = 10 * t2 + *s - '0';
                        if (t2 == 0)
                          {
                            /* Provoke with `sort -k1.0' */
                            error (0, 0, _("starting field character offset \
argument to the `-k' option\nmust be positive"));
                            badfieldspec (argv[i]);
                          }
                        --t2;
                      }
                    if (t2 || t)
                      {
                        key->sword = t;
                        key->schar = t2;
                      }
                    else
                      key->sword = -1;
                    s = set_ordering (s, key, bl_start);
                    if (*s == 0)
                      {
                        key->eword = -1;
                        key->echar = 0;
                      }
                    else if (*s != ',')
                      badfieldspec (argv[i]);
                    else if (*s == ',')
                      {
                        /* Skip over comma.  */
                        ++s;
                        if (*s == 0)
                          {
                            /* Provoke with `sort -k1,' */
                            error (0, 0, _("field specification has `,' but \
lacks following field spec"));
                            badfieldspec (argv[i]);
                          }
                        /* Get POS2. */
                        for (t = 0; ISDIGIT (*s); ++s)
                          t = t * 10 + *s - '0';
                        if (t == 0)
                          {
                            /* Provoke with `sort -k1,0' */
                            error (0, 0, _("ending field number argument \
to the `-k' option must be positive"));
                            badfieldspec (argv[i]);
                          }
                        --t;
                        t2 = 0;
                        if (*s == '.')
                          {
                            if (!ISDIGIT (s[1]))
                              {
                                /* Provoke with `sort -k1,1.' */
                                error (0, 0, _("ending field spec has `.' \
but lacks following character offset"));
                                badfieldspec (argv[i]);
                              }
                            for (++s; ISDIGIT (*s); ++s)
                              t2 = t2 * 10 + *s - '0';
                          }
                        else
                          {
                            /* `-k 2,3' is equivalent to `+1 -3'.  */
                            ++t;
                          }
                        key->eword = t;
                        key->echar = t2;
                        s = set_ordering (s, key, bl_end);
                        if (*s)
                          badfieldspec (argv[i]);
                      }
                    insertkey (key);
                    key = NULL;
                    goto outer;
                  case 'm':
                    mergeonly = 1;
                    break;
                  case 'o':
                    if (s[1])
                      outfile = s + 1;
                    else
                      {
                        if (i == argc - 1)
                          error (SORT_FAILURE, 0,
                                 _("option `-o' requires an argument"));
                        else
                          outfile = argv[++i];
                      }
                    goto outer;
                  case 's':
                    stable = 1;
                    break;
                  case 't':
                    if (s[1])
                      tab = *++s;
                    else if (i < argc - 1)
                      {
                        tab = *argv[++i];
                        goto outer;
                      }
                    else
                      error (SORT_FAILURE, 0,
                             _("option `-t' requires an argument"));
                    break;
                  case 'T':
                    if (s[1])
                      temp_dir = ++s;
                    else
                      {
                        if (i < argc - 1)
                          temp_dir = argv[++i];
                        else
                          error (SORT_FAILURE, 0,
                                 _("option `-T' requires an argument"));
                      }
                    goto outer;
                    /* break; */
                  case 'u':
                    unique = 1;
                    break;
                  case 'z':
                    eolchar = 0;
                    break;
                  case 'y':
                    /* Accept and ignore e.g. -y0 for compatibility with
                       Solaris 2.  */
                    goto outer;
                  default:
                    fprintf (stderr, _("%s: unrecognized option `-%c'\n"),
                             argv[0], *s);
                    usage (SORT_FAILURE);
                  }
                if (*s)
                  ++s;
              }
        }
      else                      /* Not an option. */
        {
          files[nfiles++] = argv[i];
        }
    outer:;
    }

  if (key)
    insertkey (key);

  /* Inheritance of global options to individual keys. */
  for (key = keyhead.next; key; key = key->next)
    if (!key->ignore && !key->translate && !key->skipsblanks && !key->reverse
        && !key->skipeblanks && !key->month && !key->numeric
        && !key->general_numeric)
      {
        key->ignore = gkey.ignore;
        key->translate = gkey.translate;
        key->skipsblanks = gkey.skipsblanks;
        key->skipeblanks = gkey.skipeblanks;
        key->month = gkey.month;
        key->numeric = gkey.numeric;
        key->general_numeric = gkey.general_numeric;
        key->reverse = gkey.reverse;
      }

  if (!keyhead.next && (gkey.ignore || gkey.translate || gkey.skipsblanks
                        || gkey.skipeblanks || gkey.month || gkey.numeric
                        || gkey.general_numeric))
    insertkey (&gkey);
  reverse = gkey.reverse;

  if (nfiles == 0)
    {
      nfiles = 1;
      files = &minus;
    }

  if (checkonly)
    {
      /* POSIX requires that sort return 1 IFF invoked with -c and the
         input is not properly sorted.  */
      exit (check (files, nfiles) == 0 ? 0 : 1);
    }

  if (!STREQ (outfile, "-"))
    {
      struct stat outstat;
      if (stat (outfile, &outstat) == 0)
        {
          /* The following code prevents a race condition when
             people use the brain dead shell programming idiom:
                  cat file | sort -o file
             This feature is provided for historical compatibility,
             but we strongly discourage ever relying on this in
             new shell programs. */

          /* Temporarily copy each input file that might be another name
             for the output file.  When in doubt (e.g. a pipe), copy.  */
          for (i = 0; i < nfiles; ++i)
            {
              char buf[8192];
              FILE *in_fp;
              FILE *out_fp;
              int cc;

              if (S_ISREG (outstat.st_mode) && !STREQ (outfile, files[i]))
                {
                  struct stat instat;
                  if ((STREQ (files[i], "-")
                       ? fstat (STDIN_FILENO, &instat)
                       : stat (files[i], &instat)) != 0)
                    {
                      error (0, errno, "%s", files[i]);
                      cleanup ();
                      exit (SORT_FAILURE);
                    }
                  if (S_ISREG (instat.st_mode) && !SAME_INODE (instat, outstat))
                    {
                      /* We know the files are distinct.  */
                      continue;
                    }
                }

              in_fp = xfopen (files[i], "r");
              tmp = tempname ();
              out_fp = xtmpfopen (tmp);
              /* FIXME: maybe use copy.c(copy) here. */
              while ((cc = fread (buf, 1, sizeof buf, in_fp)) > 0)
                write_bytes (buf, cc, out_fp, tmp);
              if (ferror (in_fp))
                {
                  error (0, errno, "%s", files[i]);
                  cleanup ();
                  exit (SORT_FAILURE);
                }
              xfclose (out_fp);
              xfclose (in_fp);
              files[i] = tmp;
            }
          ofp = xfopen (outfile, "w");
        }
      else
        {
          /* A non-`-' outfile was specified, but the file doesn't yet exist.
             Before opening it for writing (thus creating it), make sure all
             of the input files exist.  Otherwise, creating the output file
             could create an otherwise missing input file, making sort succeed
             when it should fail.  */
          for (i = 0; i < nfiles; ++i)
            {
              struct stat sb;
              if (STREQ (files[i], "-"))
                continue;
              if (stat (files[i], &sb))
                {
                  error (0, errno, "%s", files[i]);
                  cleanup ();
                  exit (SORT_FAILURE);
                }
            }

          ofp = xfopen (outfile, "w");
        }
    }
  else
    {
      ofp = stdout;
    }

  if (mergeonly)
    merge (files, nfiles, ofp, outfile);
  else
    sort (files, nfiles, ofp, outfile);
  cleanup ();

  /* If we wait for the implicit flush on exit, and the parent process
     has closed stdout (e.g., exec >&- in a shell), then the output file
     winds up empty.  I don't understand why.  This is under SunOS,
     Solaris, Ultrix, and Irix.  This premature fflush makes the output
     reappear. --karl@cs.umb.edu  */
  if (fflush (ofp) < 0)
    error (SORT_FAILURE, errno, _("%s: write error"), outfile);

  if (have_read_stdin && fclose (stdin) == EOF)
    error (SORT_FAILURE, errno, "%s", outfile);
  if (ferror (stdout) || fclose (stdout) == EOF)
    error (SORT_FAILURE, errno, _("%s: write error"), outfile);

  exit (EXIT_SUCCESS);
}