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

Copyright (C) 1987-2009 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 3 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.

$PRODUCES shift.c

#include <config.h>

#if defined (HAVE_UNISTD_H)
#  ifdef _MINIX
#    include <sys/types.h>
#  endif
#  include <unistd.h>
#endif

#include "../bashansi.h"
#include "../bashintl.h"

#include "../shell.h"
#include "common.h"

$BUILTIN shift
$FUNCTION shift_builtin
$SHORT_DOC shift [n]
Shift positional parameters.

Rename the positional parameters $N+1,$N+2 ... to $1,$2 ...  If N is
not given, it is assumed to be 1.

Exit Status:
Returns success unless N is negative or greater than $#.
$END

int print_shift_error;

/* Shift the arguments ``left''.  Shift DOLLAR_VARS down then take one
   off of REST_OF_ARGS and place it into DOLLAR_VARS[9].  If LIST has
   anything in it, it is a number which says where to start the
   shifting.  Return > 0 if `times' > $#, otherwise 0. */
int
shift_builtin (list)
     WORD_LIST *list;
{
  intmax_t times;
  register int count;
  WORD_LIST *temp;

  CHECK_HELPOPT (list);

  if (get_numeric_arg (list, 0, &times) == 0)
    return (EXECUTION_FAILURE);

  if (times == 0)
    return (EXECUTION_SUCCESS);
  else if (times < 0)
    {
      sh_erange (list ? list->word->word : NULL, _("shift count"));
      return (EXECUTION_FAILURE);
    }
  else if (times > number_of_args ())
    {
      if (print_shift_error)
	sh_erange (list ? list->word->word : NULL, _("shift count"));
      return (EXECUTION_FAILURE);
    }

  while (times-- > 0)
    {
      if (dollar_vars[1])
	free (dollar_vars[1]);

      for (count = 1; count < 9; count++)
	dollar_vars[count] = dollar_vars[count + 1];

      if (rest_of_args)
	{
	  temp = rest_of_args;
	  dollar_vars[9] = savestring (temp->word->word);
	  rest_of_args = rest_of_args->next;
	  temp->next = (WORD_LIST *)NULL;
	  dispose_words (temp);
	}
      else
	dollar_vars[9] = (char *)NULL;
    }

  invalidate_cached_quoted_dollar_at ();

  return (EXECUTION_SUCCESS);
}