source: trunk/essentials/app-shells/bash/builtins/let.def@ 3263

This file is let.def, from which is created let.c.
It implements the builtin "let" 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.

$BUILTIN let
$FUNCTION let_builtin
$PRODUCES let.c
$SHORT_DOC let arg [arg ...]
Each ARG is an arithmetic expression to be evaluated.  Evaluation
is done in fixed-width integers with no check for overflow, though
division by 0 is trapped and flagged as an error.  The following
list of operators is grouped into levels of equal-precedence operators.
The levels are listed in order of decreasing precedence.

        id++, id--      variable post-increment, post-decrement
        ++id, --id      variable pre-increment, pre-decrement
        -, +            unary minus, plus
        !, ~            logical and bitwise negation
        **              exponentiation
        *, /, %         multiplication, division, remainder
        +, -            addition, subtraction
        <<, >>          left and right bitwise shifts
        <=, >=, <, >    comparison
        ==, !=          equality, inequality
        &               bitwise AND
        ^               bitwise XOR
        |               bitwise OR
        &&              logical AND
        ||              logical OR
        expr ? expr : expr
                        conditional operator
        =, *=, /=, %=,
        +=, -=, <<=, >>=,
        &=, ^=, |=      assignment

Shell variables are allowed as operands.  The name of the variable
is replaced by its value (coerced to a fixed-width integer) within
an expression.  The variable need not have its integer attribute
turned on to be used in an expression.

Operators are evaluated in order of precedence.  Sub-expressions in
parentheses are evaluated first and may override the precedence
rules above.

If the last ARG evaluates to 0, let returns 1; 0 is returned
otherwise.
$END

#include <config.h>

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

#include "../bashintl.h"

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

/* Arithmetic LET function. */
int
let_builtin (list)
     WORD_LIST *list;
{
  intmax_t ret;
  int expok;

  /* Skip over leading `--' argument. */
  if (list && list->word && ISOPTION (list->word->word, '-'))
    list = list->next;

  if (list == 0)
    {
      builtin_error (_("expression expected"));
      return (EXECUTION_FAILURE);
    }

  for (; list; list = list->next)
    {
      ret = evalexp (list->word->word, &expok);
      if (expok == 0)
        return (EXECUTION_FAILURE);
    }

  return ((ret == 0) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
}

#ifdef INCLUDE_UNUSED
int
exp_builtin (list)
     WORD_LIST *list;
{
  char *exp;
  intmax_t ret;
  int expok;

  if (list == 0)
    {
      builtin_error (_("expression expected"));
      return (EXECUTION_FAILURE);
    }

  exp = string_list (list);
  ret = evalexp (exp, &expok);
  (void)free (exp);
  return (((ret == 0) || (expok == 0)) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
}
#endif