How to split string by string (multi-character) separator into an array?

Question

Basically I'd like to split a string into an array by a string separator like sep. for example. Is there native bash way to do this without using tools like sed, awk, etc? I know I can split a string into an array by setting IFS and using read -ra but that doesn't work with string separators. And if there is not how you'd do it with tools like sed, awk, etc?

Let's say I have the string This is some sep.string and I'd like to split it into an array with 2 elements: This is some and string.

Answer 1

You could manually iterate through the variable with parameter expansion:

#!/bin/bash
var='This is some sep.string
with
newlines
sep.another line'

a=()
while [[ $var =~ sep\. ]]
do
  e=${var%%sep.*}
  a+=("${e}")
  var=${var#${e}sep.}
done
a+=("${var}")

This loops over the variable (updating it in the process), stripping off the first separator onwards (%% looks for the longest match, so this will track backwards from the end of the string until the first instance of sep.); it adds that remainder into the array then strips that remainder and the separator off from the front of the variable. Iterate until the variable does not contain a separator any more, then add any remainder into the array.

Answer 2

Sort of a native way to do it using both parameter expansion and readarray

string='This is some sep.string'
mapfile -t array < <( echo "${string//sep./$'\n'}" )

${string//sep./$'\n'} - Will replace occurrences of sep. with a newline. mapfile/readarray will create an array with each line in it's own element.