source: vendor/bash/3.1-p17/builtins/echo.def

This file is echo.def, from which is created echo.c.
It implements the builtin "echo" in Bash.

Copyright (C) 1987-2002 Free Software Foundation, Inc.

This file is part of GNU Bash, the Bourne Again SHell.

Bash 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.

Bash 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 Bash; see the file COPYING.  If not, write to the Free Software
Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA.

$PRODUCES echo.c
#include <config.h>

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#include "../bashansi.h"

#include <stdio.h>
#include "../shell.h"

$BUILTIN echo
$FUNCTION echo_builtin
$DEPENDS_ON V9_ECHO
$SHORT_DOC 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
        \E      escape character
        \f      form feed
        \n      new line
        \r      carriage return
        \t      horizontal tab
        \v      vertical tab
        \\      backslash
        \num    the character whose ASCII code is NUM (octal).

You can explicitly turn off the interpretation of the above characters
with the -E option.
$END

$BUILTIN echo
$FUNCTION echo_builtin
$DEPENDS_ON !V9_ECHO
$SHORT_DOC echo [-n] [arg ...]
Output the ARGs.  If -n is specified, the trailing newline is suppressed.
$END

#if defined (V9_ECHO)
#  define VALID_ECHO_OPTIONS "neE"
#else /* !V9_ECHO */
#  define VALID_ECHO_OPTIONS "n"
#endif /* !V9_ECHO */

/* System V machines already have a /bin/sh with a v9 behaviour.  We
   give Bash the identical behaviour for these machines so that the
   existing system shells won't barf.  Regrettably, the SUS v2 has
   standardized the Sys V echo behavior.  This variable is external
   so that we can have a `shopt' variable to control it at runtime. */
#if defined (DEFAULT_ECHO_TO_XPG) || defined (STRICT_POSIX)
int xpg_echo = 1;
#else
int xpg_echo = 0;
#endif /* DEFAULT_ECHO_TO_XPG */

extern int posixly_correct;

/* 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
echo_builtin (list)
     WORD_LIST *list;
{
  int display_return, do_v9, i, len;
  char *temp, *s;

  do_v9 = xpg_echo;
  display_return = 1;

  if (posixly_correct && xpg_echo)
    goto just_echo;

  for (; list && (temp = list->word->word) && *temp == '-'; list = list->next)
    {
      /* 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. */
      temp++;

      for (i = 0; temp[i]; i++)
        {
          if (strchr (VALID_ECHO_OPTIONS, temp[i]) == 0)
            break;
        }

      /* echo - and echo -<nonopt> both mean to just echo the arguments. */
      if (*temp == 0 || temp[i])
        break;

      /* All of the options in TEMP are valid options to ECHO.
         Handle them. */
      while (i = *temp++)
        {
          switch (i)
            {
            case 'n':
              display_return = 0;
              break;
#if defined (V9_ECHO)
            case 'e':
              do_v9 = 1;
              break;
            case 'E':
              do_v9 = 0;
              break;
#endif /* V9_ECHO */
            default:
              goto just_echo;   /* XXX */
            }
        }
    }

just_echo:

  clearerr (stdout);    /* clear error before writing and testing success */

  while (list)
    {
      i = len = 0;
      temp = do_v9 ? ansicstr (list->word->word, STRLEN (list->word->word), 1, &i, &len)
                   : list->word->word;
      if (temp)
        {
          if (do_v9)
            {
              for (s = temp; len > 0; len--)
                putchar (*s++);
            }
          else      
            printf ("%s", temp);
#if defined (SunOS5)
          fflush (stdout);      /* Fix for bug in SunOS 5.5 printf(3) */
#endif
        }
      if (do_v9 && temp)
        free (temp);
      list = list->next;
      if (i)
        {
          display_return = 0;
          break;
        }
      if (list)
        putchar(' ');
    }

  if (display_return)
    putchar ('\n');
  fflush (stdout);
  if (ferror (stdout))
    {
      sh_wrerror ();
      clearerr (stdout);
      return (EXECUTION_FAILURE);
    }
  return (EXECUTION_SUCCESS);
}