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>8.2. Numerical Constants</H1
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NAME="NUMCONSTANTS"
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>A shell script interprets a number
	as decimal (base 10), unless that number has a
	special prefix or notation. A number preceded by a
	<TT
CLASS="REPLACEABLE"
><I
>0</I
></TT
> is <TT
CLASS="REPLACEABLE"
><I
>octal</I
></TT
>
	(base 8). A number preceded by <TT
CLASS="REPLACEABLE"
><I
>0x</I
></TT
>
	is <TT
CLASS="REPLACEABLE"
><I
>hexadecimal</I
></TT
> (base 16). A number
	with an embedded <TT
CLASS="REPLACEABLE"
><I
>#</I
></TT
> evaluates as
	<TT
CLASS="REPLACEABLE"
><I
>BASE#NUMBER</I
></TT
> (with range and notational
	restrictions).</P
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>Example 8-4. Representation of numerical constants</B
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>   1&nbsp;#!/bin/bash
   2&nbsp;# numbers.sh: Representation of numbers in different bases.
   3&nbsp;
   4&nbsp;# Decimal: the default
   5&nbsp;let "dec = 32"
   6&nbsp;echo "decimal number = $dec"             # 32
   7&nbsp;# Nothing out of the ordinary here.
   8&nbsp;
   9&nbsp;
  10&nbsp;# Octal: numbers preceded by '0' (zero)
  11&nbsp;let "oct = 032"
  12&nbsp;echo "octal number = $oct"               # 26
  13&nbsp;# Expresses result in decimal.
  14&nbsp;# --------- ------ -- -------
  15&nbsp;
  16&nbsp;
  17&nbsp;# Hexadecimal: numbers preceded by '0x' or '0X'
  18&nbsp;let "hex = 0x32"
  19&nbsp;echo "hexadecimal number = $hex"         # 50
  20&nbsp;
  21&nbsp;echo $((0x9abc))                         # 39612
  22&nbsp;#     ^^      ^^   double-parentheses arithmetic expansion/evaluation
  23&nbsp;# Expresses result in decimal.
  24&nbsp;
  25&nbsp;
  26&nbsp;
  27&nbsp;# Other bases: BASE#NUMBER
  28&nbsp;# BASE between 2 and 64.
  29&nbsp;# NUMBER must use symbols within the BASE range, see below.
  30&nbsp;
  31&nbsp;
  32&nbsp;let "bin = 2#111100111001101"
  33&nbsp;echo "binary number = $bin"              # 31181
  34&nbsp;
  35&nbsp;let "b32 = 32#77"
  36&nbsp;echo "base-32 number = $b32"             # 231
  37&nbsp;
  38&nbsp;let "b64 = 64#@_"
  39&nbsp;echo "base-64 number = $b64"             # 4031
  40&nbsp;# This notation only works for a limited range (2 - 64) of ASCII characters.
  41&nbsp;# 10 digits + 26 lowercase characters + 26 uppercase characters + @ + _
  42&nbsp;
  43&nbsp;
  44&nbsp;echo
  45&nbsp;
  46&nbsp;echo $((36#zz)) $((2#10101010)) $((16#AF16)) $((53#1aA))
  47&nbsp;                                         # 1295 170 44822 3375
  48&nbsp;
  49&nbsp;
  50&nbsp;#  Important note:
  51&nbsp;#  --------------
  52&nbsp;#  Using a digit out of range of the specified base notation
  53&nbsp;#+ gives an error message.
  54&nbsp;
  55&nbsp;let "bad_oct = 081"
  56&nbsp;# (Partial) error message output:
  57&nbsp;#  bad_oct = 081: value too great for base (error token is "081")
  58&nbsp;#              Octal numbers use only digits in the range 0 - 7.
  59&nbsp;
  60&nbsp;exit $?   # Exit value = 1 (error)
  61&nbsp;
  62&nbsp;# Thanks, Rich Bartell and Stephane Chazelas, for clarification.</PRE
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