Creating an array from a text file in Bash

arrays bash loops scripting variable-assignment
user2856414 picture user2856414 · Jun 22, 2015 · Viewed 109.9k times · Source

A script takes a URL, parses it for the required fields, and redirects its output to be saved in a file, file.txt. The output is saved on a new line each time a field has been found.

file.txt

A Cat
A Dog
A Mouse 
etc...

I want to take file.txt and create an array from it in a new script, where every line gets to be its own string variable in the array. So far I have tried: 

#!/bin/bash

filename=file.txt
declare -a myArray
myArray=(`cat "$filename"`)

for (( i = 0 ; i < 9 ; i++))
do
  echo "Element [$i]: ${myArray[$i]}"
done

When I run this script, whitespace results in words getting split and instead of getting

Desired output

Element [0]: A Cat 
Element [1]: A Dog 
etc...

I end up getting this:

Actual output

Element [0]: A 
Element [1]: Cat 
Element [2]: A
Element [3]: Dog 
etc...

How can I adjust the loop below such that the entire string on each line will correspond one-to-one with each variable in the array?

Answer

glenn jackman picture glenn jackman · Jun 22, 2015

Use the mapfile command:

mapfile -t myArray < file.txt

The error is using for -- the idiomatic way to loop over lines of a file is:

while IFS= read -r line; do echo ">>$line<<"; done < file.txt

See BashFAQ/005 for more details.

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