Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
The array=( element1 element2 ... elementN ) initialization operation, with the help of command
substitution, makes it possible to load the contents of a text file into an array.
#!/bin/bash
filename=sample_file
# cat sample_file
#
# 1 a b c
# 2 d e fg
declare −a array1
array1=( `cat "$filename" | tr '\n' ' '`) # Loads contents
# of $filename into array1.
# list file to stdout.
# change linefeeds in file to spaces.
echo ${array1[@]}
# List the array.
# 1 a b c 2 d e fg
#
# Each whitespace−separated "word" in the file
#+ has been assigned to an element of the array.
element_count=${#array1[*]}
echo $element_count # 8
Clever scripting makes it possible to add array operations.
Example 26−5. Copying and concatenating arrays
#! /bin/bash
# CopyArray.sh
#
# This script written by Michael Zick.
# Used here with permission.
# How−To "Pass by Name & Return by Name"
#+ or "Building your own assignment statement".
CpArray_Mac() {
# Assignment Command Statement Builder
echo −n 'eval '
echo −n "$2"
echo −n '=( ${'
echo −n "$1"
echo −n '[@]} )'
# Destination name
# Source name
# That could all be a single command.
# Matter of style only.
}
declare −f CopyArray
# Function "Pointer"
Chapter 26. Arrays 298