Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
Attrib[2]="\"Thirteen Ways of Looking at a Blackbird\""
for index in 1 2 3 4 5 # Five lines.
do
printf " %s\n" "${Line[index]}"
done
for index in 1 2
do
printf "
done
# Two attribution lines.
%s\n" "${Attrib[index]}"
exit 0
Array variables have a syntax all their own, and even standard Bash commands and operators have special
options adapted for array use.
array=( zero one two three four five )
echo ${array[0]}
echo ${array:0}
echo ${array:1}
# zero
# zero
# Parameter expansion of first element.
# ero
# Parameter expansion of first element,
#+ starting at position #1 (2nd character).
echo ${#array} # 4
# Length of first element of array.
In an array context, some Bash builtins have a slightly altered meaning. For example, unset deletes array
elements, or even an entire array.
Example 26−3. Some special properties of arrays
#!/bin/bash
declare −a colors
# Permits declaring an array without specifying its size.
echo "Enter your favorite colors (separated from each other by a space)."
read −a colors # Enter at least 3 colors to demonstrate features below.
# Special option to 'read' command,
#+ allowing assignment of elements in an array.
echo
element_count=${#colors[@]}
# Special syntax to extract number of elements in array.
# element_count=${#colors[*]} works also.
#
# The "@" variable allows word splitting within quotes
#+ (extracts variables separated by whitespace).
index=0
while [ "$index" −lt "$element_count" ]
do # List all the elements in the array.
Chapter 26. Arrays 294