Advanced Bash−Scripting Guide
8.2. Numerical Constants
A shell script interprets a number as decimal (base 10), unless that number has a special prefix or notation. A number preceded by a 0 is octal (base 8). A number preceded by 0x is hexadecimal (base 16). A number with an embedded # is evaluated as BASE#NUMBER (this option is of limited usefulness because of range restrictions).
Example 8−3. Representation of numerical constants:
#!/bin/bash
#numbers.sh: Representation of numbers.
#Decimal
let "d = 32" echo "d = $d"
#Nothing out of the ordinary here.
#Octal: numbers preceded by '0' (zero) let "o = 071"
echo "o = $o"
#Expresses result in decimal.
#Hexadecimal: numbers preceded by '0x' or '0X' let "h = 0x7a"
echo "h = $h"
#Expresses result in decimal.
#Other bases: BASE#NUMBER
#BASE between 2 and 36.
let "b = 32#77" echo "b = $b"
#
# This notation only works for a limited range (2 − 36)
# ... 10 digits + 26 alpha characters = 36. let "c = 2#47" # Out of range error:
# numbers.sh: let: c = 2#47: value too great for base (error token is "2#47") echo "c = $c"
echo
echo $((36#zz)) $((2#10101010)) $((16#AF16))
exit 0
# Thanks, S.C., for clarification.
Part 3. Beyond the Basics
Table of Contents
9.Variables Revisited
9.1.Internal Variables
9.2.Manipulating Strings
9.3.Parameter Substitution
9.4.Typing variables: declare or typeset
9.5.Indirect References to Variables
8.2. Numerical Constants |
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Advanced Bash−Scripting Guide
9.6.$RANDOM: generate random integer
9.7.The Double Parentheses Construct
10.Loops and Branches
10.1.Loops
10.2.Nested Loops
10.3.Loop Control
10.4.Testing and Branching
11.Internal Commands and Builtins
11.1.Job Control Commands
12.External Filters, Programs and Commands
12.1.Basic Commands
12.2.Complex Commands
12.3.Time / Date Commands
12.4.Text Processing Commands
12.5.File and Archiving Commands
12.6.Communications Commands
12.7.Terminal Control Commands
12.8.Math Commands
12.9.Miscellaneous Commands
13.System and Administrative Commands
14.Command Substitution
15.Arithmetic Expansion
16.I/O Redirection
16.1.Using exec
16.2.Redirecting Code Blocks
16.3.Applications
17.Here Documents
18.Recess Time
8.2. Numerical Constants |
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