coreutils/src/echo.c

/* 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")

/* echo [-neE] [arg ...]
Output the ARGs.  If -n is specified, the trailing newline is
suppressed.  If the -e option is given, interpretation of the
following backslash-escaped characters is turned on:
	\a	alert (bell)
	\b	backspace
	\c	suppress trailing newline
	\f	form feed
	\n	new line
	\r	carriage return
	\t	horizontal tab
	\v	vertical tab
	\\	backslash
	\0NNN	the character whose ASCII code is NNN (octal).

You can explicitly turn off the interpretation of the above characters
on System V systems with the -E option.
*/

/* 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
	       ? "\
  -e             enable interpretation of backslash escapes (default)\n\
  -E             disable interpretation of backslash escapes\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     suppress trailing newline\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);
}