1 This file is let.def, from which is created let.c.
2 It implements the builtin "let" in Bash.
4 Copyright (C) 1987-2002 Free Software Foundation, Inc.
6 This file is part of GNU Bash, the Bourne Again SHell.
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 2, or (at your option) any later
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
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, 59 Temple Place, Suite 330, Boston, MA 02111 USA.
25 $SHORT_DOC let arg [arg ...]
26 Each ARG is an arithmetic expression to be evaluated. Evaluation
27 is done in fixed-width integers with no check for overflow, though
28 division by 0 is trapped and flagged as an error. The following
29 list of operators is grouped into levels of equal-precedence operators.
30 The levels are listed in order of decreasing precedence.
32 id++, id-- variable post-increment, post-decrement
33 ++id, --id variable pre-increment, pre-decrement
34 -, + unary minus, plus
35 !, ~ logical and bitwise negation
37 *, /, % multiplication, division, remainder
38 +, - addition, subtraction
39 <<, >> left and right bitwise shifts
40 <=, >=, <, > comparison
41 ==, != equality, inequality
48 conditional expression
53 Shell variables are allowed as operands. The name of the variable
54 is replaced by its value (coerced to a fixed-width integer) within
55 an expression. The variable need not have its integer attribute
56 turned on to be used in an expression.
58 Operators are evaluated in order of precedence. Sub-expressions in
59 parentheses are evaluated first and may override the precedence
62 If the last ARG evaluates to 0, let returns 1; 0 is returned
68 #if defined (HAVE_UNISTD_H)
70 # include <sys/types.h>
78 /* Arithmetic LET function. */
86 /* Skip over leading `--' argument. */
87 if (list && list->word && ISOPTION (list->word->word, '-'))
92 builtin_error ("expression expected");
93 return (EXECUTION_FAILURE);
96 for (; list; list = list->next)
98 ret = evalexp (list->word->word, &expok);
100 return (EXECUTION_FAILURE);
103 return ((ret == 0) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
106 #ifdef INCLUDE_UNUSED
117 builtin_error ("expression expected");
118 return (EXECUTION_FAILURE);
121 exp = string_list (list);
122 ret = evalexp (exp, &expok);
124 return (((ret == 0) || (expok == 0)) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);