BASH Iterating into an array from a file [duplicate] - bash

Question

This question already has answers here:
Creating an array from a text file in Bash
(7 answers)
Closed 2 years ago.
If I have document and want to iterate the second column of the document into an array, would there be a simple way to do this. At present I am trying by using:
cat file.txt | awk -F'\t' '{print $2}' | sort -u
This lists all the unique items in the second column to standard out.
The question is ...how do I now add these items to an array, considering some of these items have whitespace.
I have been trying to declare an array
arr=()
and then tried
${arr}<<cat file.txt | awk -F'\t' '{print $2}' | sort -u

Answer 1

Bash4+ has mapfile aka readarray plus a Process Substituion.
mapfile -t array < <(awk -F'\t' '{print $2}' file.txt | sort -u)
If you don't have bash4+
while IFS= read -r line; do
array+=("$line")
done < <(awk -F'\t' '{print $2}' file.txt | sort -u)
To see the structure in the array
declare -p array
By default read strips leading and trailing white space so to work around that you need to use IFS= to preserve the default line structure.
The -t option from mapfile -t Remove a trailing DELIM from each line read (default newline)

Answer 2

Bash 3 has read -a to read IFS delimited fields from a file stream to an array.
The -d '' switch tells read, the record delimiter is null, so it reads fields until it reaches the end of the file stream EOF or a null character.
declare -a my_array
IFS=$'\n' read -r -d '' -a my_array < <(cut -f2 < file.txt | sort -u)