Bash array usage cheatsheet.

README.md

Bash array usage cheatsheet

• Creation
• Get elements
• Append element
• Array length
• Iteration
• Pass array to function
• Reference

Creation

# empty
myArray=()

# with elements
myArray=("first" "second" "third item" "fourth")

myArray=(
  "first"
  "second"
  "third item"
  "fourth"
)

Get elements

# all elements - space delimited
$ echo ${myArray[@]}

# all elements - separate words
$ echo "${myArray[@]}"

# all elements - single word, separated by first character of IFS
$ IFS="-"
$ echo "${myArray[*]}"

# specific element
$ echo "${myArray[1]}"

# two elements, starting at second item
$ echo "${myArray[@]:1:2}"

# keys (indicies) of an array
$ echo "${!myArray[@]}"

Append element

myArray=()
myArray+=("item")

Array length

# element count
$ echo "${#myArray[@]}"

# length of specific element (string length)
$ echo "${#myArray[1]}"

Iteration

for arrayItem in "${myArray[@]}"; do
  echo "$arrayItem"
done

Pass array to function

Note

Named reference to another variable (local -n) only supported with Bash 4.3.x or above.

function myFunction {
  local -n givenList=$1
  echo "${givenList[@]}"
}

itemList=("first" "second" "third")
myFunction itemList

Reference

• https://tldp.org/LDP/Bash-Beginners-Guide/html/sect_10_02.html
• https://www.thegeekstuff.com/2010/06/bash-array-tutorial
• https://www.tecmint.com/working-with-arrays-in-linux-shell-scripting/
• https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Arrays

Note: namerefs only work in bash 4.3.x... I've updated on my fork: https://gist.github.com/pstephens/7d7cfcdcf9f1e0a26f7ffba1e9399ef7/revisions

Thank you @pstephens - have updated 👍