 |  |
B.8. Arithmetic
Starting with ksh93m, the built-in arithmetic facility understands a large percentage of the C language's expressions. This makes the shell more attractive as a full-blown programming language. The following features are available:
- Trailing type suffixes
- Integer constants can have a trailing U or L suffix to indicate that they are unsigned or long, respectively. While the lowercase versions may also be used, this is not recommended, since it is easy to confuse an l (letter ell) with a 1 (digit one).
- C character constants
-
C single-quoted character constants are recognized.
As in C, they act like integer constants. For example:
$ typeset -i c $ for ((c = 'a'; c <= 'z'; c++)) > do print $c > done 97 98 99 100 ...
- Octal and hexadecimal constants
-
You can use the C format for octal (base 8) and hexadecimal
(base 16) constants. Octal constants start with a leading 0,
and hexadecimal constants start with a leading 0x
or 0X.
For example:
$ print $((010 + 1)) Octal 10 is decimal 8 9 $ print $((0x10 + 1)) Hexadecimal 10 is decimal 16 17
- Unsigned integer arithmetic
-
By using typeset -ui, you can create
unsigned integers. Regular integers represent both positive
and negative numbers. Unsigned integers start at 0, go up
to some implementation-dependent value, and then "wrap"
around again to 0. Similarly, subtracting 1 from 0
wraps around the other way, yielding the largest unsigned number:
$ typeset -ui u=0 $ let u-- $ print $u 4294967295
- C operators and precedence
- ksh supports the full set of C operators, with the same precedence and associativity. The operators were presented in detail in Chapter 6 and are summarized again below.
| Operator | Meaning | Associativity |
|---|---|---|
| ++ -- | Increment and decrement, prefix and postfix | Left to right |
| + - ! ~ | Unary plus and minus; logical and bitwise negation | Right to left |
| ** | Exponentiation[157] |
Right to left |
| * / % | Multiplication, division, and remainder | Left to right |
| + - | Addition and subtraction | Left to right |
| << >> | Bit-shift left and right | Left to right |
| < <= > >= | Comparisons | Left to right |
| == != | Equal and not equal | Left to right |
| & | Bitwise and | Left to right |
| ^ | Bitwise exclusive-or | Left to right |
| | | Bitwise or | Left to right |
| && | Logical and (short circuit) | Left to right |
| || | Logical or (short circuit) | Left to right |
| ?: | Conditional expression | Right to left |
= += -= *= /= %= &= ^= <<= >>= |
Assignment operators | Right to left |
| , | Sequential evaluation | Left to right |
[157] ksh93m and newer. The ** operator is not in the C language.
|  | |
| B.7. Typeset Options |  | B.9. Emacs Mode Commands |
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