/* cat -- concatenate files and print on the standard output.
   Copyright (C) 1988-2026 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 3 of the License, 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, see <https://www.gnu.org/licenses/>.  */

/* Differences from the Unix cat:
   * Always unbuffered, -u is ignored.
   * Usually much faster than other versions of cat, the difference
   is especially apparent when using the -v option.

   By tege@sics.se, Torbjörn Granlund, advised by rms, Richard Stallman.  */

#include <config.h>

#include <stdio.h>
#include <getopt.h>
#include <sys/types.h>

#if HAVE_STROPTS_H
# include <stropts.h>
#endif
#include <sys/ioctl.h>

#include "system.h"
#include "alignalloc.h"
#include "ioblksize.h"
#include "fadvise.h"
#include "full-write.h"
#include "xbinary-io.h"

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

#define AUTHORS \
  proper_name_lite ("Torbjorn Granlund", "Torbj\303\266rn Granlund"), \
  proper_name ("Richard M. Stallman")

/* Name of input file.  May be "-".  */
static char const *infile;

/* Descriptor on which input file is open.  */
static int input_desc;

/* Buffer for line numbers.
   An 11 digit counter may overflow within an hour on a P2/466,
   an 18 digit counter needs about 1000y */
#define LINE_COUNTER_BUF_LEN 20
static char line_buf[LINE_COUNTER_BUF_LEN] =
  {
    ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ',
    ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', '0',
    '\t', '\0'
  };

/* Position in 'line_buf' where printing starts.  This will not change
   unless the number of lines is larger than 999999.  */
static char *line_num_print = line_buf + LINE_COUNTER_BUF_LEN - 8;

/* Position of the first digit in 'line_buf'.  */
static char *line_num_start = line_buf + LINE_COUNTER_BUF_LEN - 3;

/* Position of the last digit in 'line_buf'.  */
static char *line_num_end = line_buf + LINE_COUNTER_BUF_LEN - 3;

/* Preserves the 'cat' function's local 'newlines' between invocations.  */
static int newlines2 = 0;

/* Whether there is a pending CR to process.  */
static bool pending_cr = false;

void
usage (int status)
{
  if (status != EXIT_SUCCESS)
    emit_try_help ();
  else
    {
      printf (_("\
Usage: %s [OPTION]... [FILE]...\n\
"),
              program_name);
      fputs (_("\
Concatenate FILE(s) to standard output.\n\
"), stdout);

      emit_stdin_note ();

      fputs (_("\
\n\
  -A, --show-all           equivalent to -vET\n\
  -b, --number-nonblank    number nonempty output lines, overrides -n\n\
  -e                       equivalent to -vE\n\
  -E, --show-ends          display $ or ^M$ at end of each line\n\
  -n, --number             number all output lines\n\
  -s, --squeeze-blank      suppress repeated empty output lines\n\
"), stdout);
      fputs (_("\
  -t                       equivalent to -vT\n\
  -T, --show-tabs          display TAB characters as ^I\n\
  -u                       (ignored)\n\
  -v, --show-nonprinting   use ^ and M- notation, except for LFD and TAB\n\
"), stdout);
      fputs (HELP_OPTION_DESCRIPTION, stdout);
      fputs (VERSION_OPTION_DESCRIPTION, stdout);
      printf (_("\
\n\
Examples:\n\
  %s f - g  Output f's contents, then standard input, then g's contents.\n\
  %s        Copy standard input to standard output.\n\
"),
              program_name, program_name);
      emit_ancillary_info (PROGRAM_NAME);
    }
  exit (status);
}

/* Compute the next line number.  */