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Bash Scripting

Sorting Arrays

First we need to declare an array:

declare -a MyArray

This does not produce any output but note the small 'a' to distinguish this from an ordinary variable.

To populate the array, we can do this manually if we know the values already. We'll use a simple CD list for example.

declare -a MyTunes
Title="2CELLOS - In2ition (2013)"
MyTunes=(
"13 Benedictus.flac"
"01 Oh, Well.flac"
"02 We Found Love.flac"
"04 Every Breath You Take.flac"
"05 Supermassive Black Hole.flac"
"06 Technical Difficulties.flac"
"08 Bang Bang.flac"
"09 Voodoo People.flac"
"10 Candle in the Wind.flac"
"07 Clocks.flac"
"11 Orient Express.flac"
"12 Il Libro Dell'Amore.flac"
"03 Highway to Hell.flac"
)

Note they are NOT in the correct track order, so how do we sort that?

First we try echo, piping the result to sort:

clear
echo "Using 'echo' ..."
echo "$Title"
echo "${MyTunes[@]}" | sort

Hmmm. Not so good. Try printf:

clear
echo "Using 'printf' ..."
echo "$Title"
printf "%s\n" "${MyTunes[@]}" | sort

Much better, and correct to boot!

Using the example array from here.

declare -a SQLBooks=(
"Definitive Guide to SQLite 2E (The)"
"Practical SQL Handbook 4E (The)"
"Joe Celko's SQL For Smarties: Advanced SQL Programming 2E"
"Joe Celko's Data & Databases: Concepts In Practice"
"Database Design for Mere Mortals"
"SQL Queries for Mere Mortals"
"Using SQLite"
"Joe Celko's SQL Puzzles and Answers 2E"
)
printf "%s\n" "${SQLBooks[@]}" | sort

Again, just what we wanted:

Sort Numbers

If your array elements are integers, we can tell sort to accommodate that using -n option.

echo "Sorting numbers"
declare -a MyNumbs=(12 5 78 1 8 0 42)
IFS=$'\n' # Internal Field Separator
MyNumbsSorted=($(sort -n <<< "${MyNumbs[*]}"))
unset IFS
echo "${MyNumbsSorted[@]}"

Surprisingly ...

There are a couple of bashisms in that bit of code:

echo "Number looping ..."
for n in ${MyNumbsSorted[*]}; do
	echo $n
done