builtins/let.def

   1 This file is let.def, from which is created let.c.
   2 It implements the builtin "let" in Bash.
   3
   4 Copyright (C) 1987, 1989, 1991 Free Software Foundation, Inc.
   5
   6 This file is part of GNU Bash, the Bourne Again SHell.
   7
   8 Bash is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 1, or (at your option) any later
  11 version.
  12
  13 Bash is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 You should have received a copy of the GNU General Public License along
  19 with Bash; see the file COPYING.  If not, write to the Free Software
  20 Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  21
  22 $BUILTIN let
  23 $FUNCTION let_builtin
  24 $PRODUCES let.c
  25 $SHORT_DOC let arg [arg ...]
  26 Each ARG is an arithmetic expression to be evaluated.  Evaluation
  27 is done in long integers with no check for overflow, though division
  28 by 0 is trapped and flagged as an error.  The following list of
  29 operators is grouped into levels of equal-precedence operators.
  30 The levels are listed in order of decreasing precedence.
  31
  32         -, +            unary minus, plus
  33         !, ~            logical and bitwise negation
  34         *, /, %         multiplication, division, remainder
  35         +, -            addition, subtraction
  36         <<, >>          left and right bitwise shifts
  37         <=, >=, <, >    comparison
  38         ==, !=          equality, inequality
  39         &               bitwise AND
  40         ^               bitwise XOR
  41         |               bitwise OR
  42         &&              logical AND
  43         ||              logical OR
  44         expr ? expr : expr
  45                         conditional expression
  46         =, *=, /=, %=,
  47         +=, -=, <<=, >>=,
  48         &=, ^=, |=      assignment
  49
  50 Shell variables are allowed as operands.  The name of the variable
  51 is replaced by its value (coerced to a long integer) within
  52 an expression.  The variable need not have its integer attribute
  53 turned on to be used in an expression.
  54
  55 Operators are evaluated in order of precedence.  Sub-expressions in
  56 parentheses are evaluated first and may override the precedence
  57 rules above.
  58
  59 If the last ARG evaluates to 0, let returns 1; 0 is returned
  60 otherwise.
  61 $END
  62
  63 #include <config.h>
  64
  65 #if defined (HAVE_UNISTD_H)
  66 #  ifdef _MINIX
  67 #    include <sys/types.h>
  68 #  endif
  69 #  include <unistd.h>
  70 #endif
  71
  72 #include "../shell.h"
  73 #include "common.h"
  74
  75 /* Arithmetic LET function. */
  76 int
  77 let_builtin (list)
  78      WORD_LIST *list;
  79 {
  80   long ret;
  81   int expok;
  82
  83   if (list == 0)
  84     {
  85       builtin_error ("expression expected");
  86       return (EXECUTION_FAILURE);
  87     }
  88
  89   for (; list; list = list->next)
  90     {
  91       ret = evalexp (list->word->word, &expok);
  92       if (expok == 0)
  93         return (EXECUTION_FAILURE);
  94     }
  95
  96   return ((ret == 0L) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
  97 }
  98
  99 #ifdef INCLUDE_UNUSED
 100 int
 101 exp_builtin (list)
 102      WORD_LIST *list;
 103 {
 104   char *exp;
 105   int ret, expok;
 106
 107   if (list == 0)
 108     {
 109       builtin_error ("expression expected");
 110       return (EXECUTION_FAILURE);
 111     }
 112
 113   exp = string_list (list);
 114   ret = evalexp (exp, &expok);
 115   (void)free (exp);
 116   return (((ret == 0L) || (expok == 0)) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
 117 }
 118 #endif