How to read a space-delimited string into an array in Bash?

Question

I have a variable which contains a space-delimited string:

line="1 1.50 string"

I want to split that string with space as a delimiter and store the result in an array, so that the following:

echo ${arr[0]}
echo ${arr[1]}
echo ${arr[2]}

outputs

1
1.50
string

Somewhere I found a solution which doesn't work:

arr=$(echo ${line})

If I run the echo statements above after this, I get:

1 1.50 string
[empty line]
[empty line]

I also tried

IFS=" "
arr=$(echo ${line})

with the same result. Can someone help, please?

See this answer on Unix & Linux Stack Exchange: Using sed with herestring (<<<) and read -a. set -f; arr=($string); set +f seems to be faster than read -r -a <<< $string. — codeforester
– codeforester, Commented Mar 20, 2018 at 2:23
Related: how to convert a newline-delimited string to a bash array: Convert multiline string to array — Gabriel Staples
– Gabriel Staples, Commented Dec 17, 2021 at 20:51
See also these demonstrations and examples here: shellcheck SC2206: Quote to prevent word splitting/globbing, or split robustly with mapfile or read -a. — Gabriel Staples
– Gabriel Staples, Commented Feb 25, 2022 at 4:10

Gabriel Staples · Accepted Answer · 2022-02-19 00:07:20Z

461

In order to convert a string into an array, create an array from the string, letting the string get split naturally according to the IFS (Internal Field Separator) variable, which is the space char by default:

arr=($line)

or pass the string to the stdin of the read command using the herestring (<<<) operator:

read -a arr <<< "$line"

For the first example, it is crucial not to use quotes around $line since that is what allows the string to get split into multiple elements.

See also: https://github.com/koalaman/shellcheck/wiki/SC2206

edited Feb 19, 2022 at 0:07

Gabriel Staples

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answered Feb 15, 2012 at 13:06

kev

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Sign up to request clarification or add additional context in comments.

14 Comments

Banjer Over a year ago

and to do a sanity check of your beautiful new array: for i in ${arr[@]}; do echo $i; done

Banjer Over a year ago

or just echo ${arr[@]}

Tino Over a year ago

Both ways may fail if $line has globbing characters in it. mkdir x && cd x && touch A B C && line="*" arr=($line); echo ${#arr[@]} gives 3

Dave Over a year ago

declare -a "arr=($line)" will ignore IFS delimiters inside quoted strings

Johnny Wong Over a year ago

@Tino No. When line='*', read -a arr <<<$line always work, but only arr=($line) fails.

|

codeforester · Accepted Answer · 2018-03-19 20:22:09Z

66

In: arr=( $line ). The "split" comes associated with "glob".
Wildcards (*,? and []) will be expanded to matching filenames.

The correct solution is only slightly more complex:

IFS=' ' read -a arr <<< "$line"

No globbing problem; the split character is set in $IFS, variables quoted.

edited Mar 19, 2018 at 20:22

codeforester

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answered Nov 3, 2016 at 6:54

user8017719

5 Comments

codeforester Over a year ago

This should be the accepted answer. The statement arr=($line) in the accepted answer suffers from globbing issues. For example, try: line="twinkling *"; arr=($line); declare -p arr.

codeforester Over a year ago

Quoting is optional for herestring, <<< but it may be a good idea to still use double quotes for consistency and readability.

Gabriel Staples Over a year ago

See also: shellcheck SC2206: Quote to prevent word splitting/globbing, or split robustly with mapfile or read -a.

payne Over a year ago

I get func:read:5: bad option: -a

Charles Duffy Over a year ago

@payne, then your shell wasn't bash -- sh isn't guaranteed to support arrays at all. Be sure your script starts with #!/usr/bin/env bash not #!/bin/sh, and that you don't start it with sh scriptname.

gniourf_gniourf · Accepted Answer · 2013-09-12 20:19:11Z

61

Try this:

arr=(`echo ${line}`);

edited Sep 12, 2013 at 20:19

gniourf_gniourf

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answered Sep 12, 2013 at 20:15

Randy

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7 Comments

Keith Hughitt Over a year ago

Nice -- This solution also works in Z shell where some of the other approaches above fail.

vr3C Over a year ago

Its does the work, could you please explain why it works?

Johnny Wong Over a year ago

Remark: this doesn't work either when the line have '*' in it, like line='*'

artu-hnrq Over a year ago

Looking for a GNU Make 4.2.1 solution, but it doesn't did the job

user8017719 Over a year ago

@artu-hnrq Make use the sh shell. That shell has no arrays. The question is about arrays. Can't give you an answer compatible with both requirements. Unless you claim that the positional arguments are the only array in sh and, then, this: set -- $line; printf '%s\n' "$@" would work. Note that glob characters are still a problem in this case.

|

David Anderson · Accepted Answer · 2018-11-19 06:54:14Z

18

If you need parameter expansion, then try:

eval "arr=($line)"

For example, take the following code.

line='a b "c d" "*" *'
eval "arr=($line)"
for s in "${arr[@]}"; do 
    echo "$s"
done

If the current directory contained the files a.txt, b.txt and c.txt, then executing the code would produce the following output.

a
b
c d
*
a.txt
b.txt
c.txt

edited Nov 19, 2018 at 6:54

answered Nov 19, 2018 at 6:41

David Anderson

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2 Comments

artu-hnrq Over a year ago

Looking for a GNU Make 4.2.1 solution, but is not that

Charles Duffy Over a year ago

@artu-hnrq, why would you be looking for a makefile solution in answers to a question that isn't tagged for make and doesn't otherwise mention make in any way?

ivanleoncz · Accepted Answer · 2023-08-27 15:44:29Z

1

Yet another solution, but using readarray:

readarray -d ' ' arr <<< "argelia china denmark colombia"

Indeed, storing the input in an array of 4 positions:

$ echo ${#arr[@]} ${arr[@]:1:2}
4 china  denmark

answered Aug 27, 2023 at 15:44

ivanleoncz

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1 Comment

SpinUp __ A Davis Over a year ago

I like readarray, but you usually want to use -t with it. This is easier to see if you declare -p arr instead of using echo.

codemania · Accepted Answer · 2014-03-03 09:07:34Z

-9

line="1 1.50 string"

arr=$( $line | tr " " "\n")

for x in $arr
do
echo "> [$x]"
done

edited Mar 3, 2014 at 9:07

codemania

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answered Mar 3, 2014 at 8:50

Hitesh

9

1 Comment

Zorf Over a year ago

The looping is wrong, it splits the array fine and the pipe into tr is superfluous but it should loop over "${arr[@]}" instead, not $arr

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