1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
|
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
|
