Bash reference

${string//substring/replacement}

original_string="Foo bar foo bar foo"
replaced_string=${original_string//foo/***}

echo "$replaced_string"

if [ -z "$variable" ]; then
  echo "The variable is empty"
fi

if [ -n "$variable" ]; then
  echo "The variable is not empty"
fi

array=(
  element1
  element2
  element3
)

declare -A assoc_array
assoc_array[key1]=value1
assoc_array[key2]=value2

array+=("newElement1")
array+=("newElement2")

array[0]="element1"
array[1]="element2"
array[2]="element3"

for name in "${names[@]}"; do
do
  echo "Hello, $name!"
done

if [ -z "$1" ]; then
  echo "No first argument was passed."
else
  echo "The first argument is: $1"
fi