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) 1987-2009 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
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation, either version 3 of the License, or
  11 (at your option) any later version.
  12
  13 Bash is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with Bash.  If not, see <http://www.gnu.org/licenses/>.
  20
  21 $BUILTIN let
  22 $FUNCTION let_builtin
  23 $PRODUCES let.c
  24 $SHORT_DOC let arg [arg ...]
  25 Evaluate arithmetic expressions.
  26
  27 Evaluate each ARG as an arithmetic expression.  Evaluation is done in
  28 fixed-width integers with no check for overflow, though division by 0
  29 is trapped and flagged as an error.  The following list of operators is
  30 grouped into levels of equal-precedence operators.  The levels are listed
  31 in order of decreasing precedence.
  32
  33         id++, id--      variable post-increment, post-decrement
  34         ++id, --id      variable pre-increment, pre-decrement
  35         -, +            unary minus, plus
  36         !, ~            logical and bitwise negation
  37         **              exponentiation
  38         *, /, %         multiplication, division, remainder
  39         +, -            addition, subtraction
  40         <<, >>          left and right bitwise shifts
  41         <=, >=, <, >    comparison
  42         ==, !=          equality, inequality
  43         &               bitwise AND
  44         ^               bitwise XOR
  45         |               bitwise OR
  46         &&              logical AND
  47         ||              logical OR
  48         expr ? expr : expr
  49                         conditional operator
  50         =, *=, /=, %=,
  51         +=, -=, <<=, >>=,
  52         &=, ^=, |=      assignment
  53
  54 Shell variables are allowed as operands.  The name of the variable
  55 is replaced by its value (coerced to a fixed-width integer) within
  56 an expression.  The variable need not have its integer attribute
  57 turned on to be used in an expression.
  58
  59 Operators are evaluated in order of precedence.  Sub-expressions in
  60 parentheses are evaluated first and may override the precedence
  61 rules above.
  62
  63 Exit Status:
  64 If the last ARG evaluates to 0, let returns 1; let returns 0 otherwise.
  65 $END
  66
  67 #include <config.h>
  68
  69 #if defined (HAVE_UNISTD_H)
  70 #  ifdef _MINIX
  71 #    include <sys/types.h>
  72 #  endif
  73 #  include <unistd.h>
  74 #endif
  75
  76 #include "../bashintl.h"
  77
  78 #include "../shell.h"
  79 #include "common.h"
  80
  81 /* Arithmetic LET function. */
  82 int
  83 let_builtin (list)
  84      WORD_LIST *list;
  85 {
  86   intmax_t ret;
  87   int expok;
  88
  89   CHECK_HELPOPT (list);
  90
  91   /* Skip over leading `--' argument. */
  92   if (list && list->word && ISOPTION (list->word->word, '-'))
  93     list = list->next;
  94
  95   if (list == 0)
  96     {
  97       builtin_error (_("expression expected"));
  98       return (EXECUTION_FAILURE);
  99     }
 100
 101   for (; list; list = list->next)
 102     {
 103       ret = evalexp (list->word->word, EXP_EXPANDED, &expok);
 104       if (expok == 0)
 105         return (EXECUTION_FAILURE);
 106     }
 107
 108   return ((ret == 0) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
 109 }
 110
 111 #ifdef INCLUDE_UNUSED
 112 int
 113 exp_builtin (list)
 114      WORD_LIST *list;
 115 {
 116   char *exp;
 117   intmax_t ret;
 118   int expok;
 119
 120   if (list == 0)
 121     {
 122       builtin_error (_("expression expected"));
 123       return (EXECUTION_FAILURE);
 124     }
 125
 126   exp = string_list (list);
 127   ret = evalexp (exp, EXP_EXPANDED, &expok);
 128   (void)free (exp);
 129   return (((ret == 0) || (expok == 0)) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
 130 }
 131 #endif