/* echo.c, derived from code echo.c in Bash.
   Copyright (C) 87,89, 1991-1997, 1999-2005, 2007-2008 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 <http://www.gnu.org/licenses/>.  */

#include <config.h>
#include <stdio.h>
#include <sys/types.h>
#include "system.h"
#include "long-options.h"

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

#define AUTHORS \
  proper_name ("Brian Fox"), \
  proper_name ("Chet Ramey")

/* If true, interpret backslash escapes by default.  */
#ifndef DEFAULT_ECHO_TO_XPG
enum { DEFAULT_ECHO_TO_XPG = false };
#endif

void
usage (int status)
{
  if (status != EXIT_SUCCESS)
    fprintf (stderr, _("Try `%s --help' for more information.\n"),
	     program_name);
  else
    {
      printf (_("Usage: %s [OPTION]... [STRING]...\n"), program_name);
      fputs (_("\
Echo the STRING(s) to standard output.\n\
\n\
  -n             do not output the trailing newline\n\
"), stdout);
      fputs (_(DEFAULT_ECHO_TO_XPG
	       ? N_("\
  -e             enable interpretation of backslash escapes (default)\n\
  -E             disable interpretation of backslash escapes\n")
	       : N_("\
  -e             enable interpretation of backslash escapes\n\
  -E             disable interpretation of backslash escapes (default)\n")),
	     stdout);
      fputs (HELP_OPTION_DESCRIPTION, stdout);
      fputs (VERSION_OPTION_DESCRIPTION, stdout);
      fputs (_("\
\n\
If -e is in effect, the following sequences are recognized:\n\
\n\
  \\0NNN   the character whose ASCII code is NNN (octal)\n\
  \\\\     backslash\n\
  \\a     alert (BEL)\n\
  \\b     backspace\n\
"), stdout);
      fputs (_("\
  \\c     produce no further output\n\
  \\f     form feed\n\
  \\n     new line\n\
  \\r     carriage return\n\
  \\t     horizontal tab\n\
  \\v     vertical tab\n\
"), stdout);
      printf (USAGE_BUILTIN_WARNING, PROGRAM_NAME);
      emit_bug_reporting_address ();
    }
  exit (status);
}

/* Convert C from hexadecimal character to integer.  */
static int
hextobin (unsigned char c)
{
  switch (c)
    {
    default: return c - '0';
    case 'a': case 'A': return 10;
    case 'b': case 'B': return 11;
    case 'c': case 'C': return 12;
    case 'd': case 'D': return 13;
    case 'e': case 'E': return 14;
    case 'f': case 'F': return 15;
    }
}

/* Print the words in LIST to standard output.  If the first word is
   `-n', then don't print a trailing newline.  We also support the
   echo syntax from Version 9 unix systems. */

int
main (int argc, char **argv)
{
  bool display_return = true;
  bool allow_options =
    (! getenv ("POSIXLY_CORRECT")
     || (! DEFAULT_ECHO_TO_XPG && 1 < argc && STREQ (argv[1], "-n")));

  /* System V machines already have a /bin/sh with a v9 behavior.
     Use the identical behavior for these machines so that the
     existing system shell scripts won't barf.  */
  bool do_v9 = DEFAULT_ECHO_TO_XPG;

  initialize_main (&argc, &argv);
  set_program_name (argv[0]);
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

  atexit (close_stdout);

  if (allow_options)
    parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, Version,
			usage, AUTHORS, (char const *) NULL);

  --argc;
  ++argv;

  if (allow_options)
    while (argc > 0 && *argv[0] == '-')
      {
	char const *temp = argv[0] + 1;
	size_t i;

	/* If it appears that we are handling options, then make sure that
	   all of the options specified are actually valid.  Otherwise, the
	   string should just be echoed.  */

	for (i = 0; temp[i]; i++)
	  switch (temp[i])
	    {
	    case 'e': case 'E': case 'n':
	      break;
	    default:
	      goto just_echo;
	    }

	if (i == 0)
	  goto just_echo;

	/* All of the options in TEMP are valid options to ECHO.
	   Handle them. */
	while (*temp)
	  switch (*temp++)
	    {
	    case 'e':
	      do_v9 = true;
	      break;

	    case 'E':
	      do_v9 = false;
	      break;

	    case 'n':
	      display_return = false;
	      break;
	    }

	argc--;
	argv++;
      }

just_echo:

  if (do_v9)
    {
      while (argc > 0)
	{
	  char const *s = argv[0];
	  unsigned char c;

	  while ((c = *s++))
	    {
	      if (c == '\\' && *s)
		{
		  switch (c = *s++)
		    {
		    case 'a': c = '\a'; break;
		    case 'b': c = '\b'; break;
		    case 'c': exit (EXIT_SUCCESS);
		    case 'f': c = '\f'; break;
		    case 'n': c = '\n'; break;
		    case 'r': c = '\r'; break;
		    case 't': c = '\t'; break;
		    case 'v': c = '\v'; break;
		    case 'x':
		      {
			unsigned char ch = *s;
			if (! isxdigit (ch))
			  goto not_an_escape;
			s++;
			c = hextobin (ch);
			ch = *s;
			if (isxdigit (ch))
			  {
			    s++;
			    c = c * 16 + hextobin (ch);
			  }
		      }
		      break;
		    case '0':
		      c = 0;
		      if (! ('0' <= *s && *s <= '7'))
			break;
		      c = *s++;
		      /* Fall through.  */
		    case '1': case '2': case '3':
		    case '4': case '5': case '6': case '7':
		      c -= '0';
		      if ('0' <= *s && *s <= '7')
			c = c * 8 + (*s++ - '0');
		      if ('0' <= *s && *s <= '7')
			c = c * 8 + (*s++ - '0');
		      break;
		    case '\\': break;

		    not_an_escape:
		    default:  putchar ('\\'); break;
		    }
		}
	      putchar (c);
	    }
	  argc--;
	  argv++;
	  if (argc > 0)
	    putchar (' ');
	}
    }
  else
    {
      while (argc > 0)
	{
	  fputs (argv[0], stdout);
	  argc--;
	  argv++;
	  if (argc > 0)
	    putchar (' ');
	}
    }

  if (display_return)
    putchar ('\n');
  exit (EXIT_SUCCESS);
}