How to split a string into an array in Bash?

Question

In a Bash script, I would like to split a line into pieces and store them in an array.

For example, given the line:

Paris, France, Europe

I would like to have the resulting array to look like so:

array[0] = Paris
array[1] = France
array[2] = Europe

A simple implementation is preferable; speed does not matter. How can I do it?

Answer 1

IFS=', ' read -r -a array <<< "$string"

Note that the characters in $IFS are treated individually as separators so that in this case fields may be separated by either a comma or a space rather than the sequence of the two characters. Interestingly though, empty fields aren't created when comma-space appears in the input because the space is treated specially.

To access an individual element:

echo "${array[0]}"

To iterate over the elements:

for element in "${array[@]}"
do
    echo "$element"
done

To get both the index and the value:

for index in "${!array[@]}"
do
    echo "$index ${array[index]}"
done

The last example is useful because Bash arrays are sparse. In other words, you can delete an element or add an element and then the indices are not contiguous.

unset "array[1]"
array[42]=Earth

To get the number of elements in an array:

echo "${#array[@]}"

As mentioned above, arrays can be sparse so you shouldn't use the length to get the last element. Here's how you can in Bash 4.2 and later:

echo "${array[-1]}"

in any version of Bash (from somewhere after 2.05b):

echo "${array[@]: -1:1}"

Larger negative offsets select farther from the end of the array. Note the space before the minus sign in the older form. It is required.