How to assign a multiple line value to a bash variable

Question

I have a variable FOO with me that needs to be assigned with a value that will be multiple lines. Something like this,

FOO="This is line 1
     This is line 2
     This is line 3"

So when I print the value of FOO it should give the following output.

echo $FOO
output:
This is line 1
This is line 2
This is line 3

Furthermore, the number of lines will be decided dynamically as I will initialize it using a loop.

The answers that have been shown in the other question using mainly read -d is not suitable for me as I am doing intensive string operations and the code format is also important.

Remove leading whitespaces in line 2 and 3 and use: echo "$FOO" — Cyrus
– Cyrus, Commented Jun 29, 2016 at 4:52

John Kugelman · Accepted Answer · 2016-06-29 04:59:51Z

36

Don't indent the lines or you'll get extra spaces. Use quotes when you expand "$FOO" to ensure the newlines are preserved.

$ FOO="This is line 1 
This is line 2   
This is line 3"
$ echo "$FOO"
This is line 1
This is line 2
This is line 3

Another way is to use \n escape sequences. They're interpreted inside of $'...' strings.

$ FOO=$'This is line 1\nThis is line 2\nThis is line 3'
$ echo "$FOO"

A third way is to store the characters \ and n, and then have echo -e interpret the escape sequences. It's a subtle difference. The important part is that \n isn't interpreted inside of regular quotes.

$ FOO='This is line 1\nThis is line 2\nThis is line 3'
$ echo -e "$FOO"
This is line 1
This is line 2
This is line 3

You can see the distinction I'm making if you remove the -e option and have echo print the raw string without interpreting anything.

$ echo "$FOO"
This is line 1\nThis is line 2\nThis is line 3

answered Jun 29, 2016 at 4:59

John Kugelman

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2 Comments

yaobin Over a year ago

Hi John, your example code works for me! However, in the first example above, when I echo the variable with echo $FOO without putting $FOO between the quotation marks, the output is on the same line. Do you know why? I'm using GNU bash, version 4.3.11(1)-release on Ubuntu 14.04.

John Kugelman Over a year ago

That's what happens when you don't have quotes. The value is subject to word splitting and glob expansion. Instead of echo being told to print one argument with embedded newlines, each word of $FOO becomes a separate argument with no newlines. It's as if you wrote echo This is line 1 This is line 2 This is line 3. Bottom line: always quote variable expansions unless you actually want it to be subject to word splitting and globbing (rare).

Community · Accepted Answer · 2017-05-23 11:33:24Z

5

When you initialize FOO you should use line breaks: \n.

FOO="This is line 1\nThis is line 2\nThis is line 3"

Then use echo -e to output FOO.

It is important to note that \n inside "..." is NOT a line break, but literal \ , followed by literal n. It is only when interpreted by echo -e that this literal sequence is converted to a newline character. — wise words from mklement0

#!/bin/bash

FOO="This is line 1\nThis is line 2\nThis is line 3"
echo -e $FOO

Output:
This is line 1
This is line 2
This is line 3

edited May 23, 2017 at 11:33

CommunityBot

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answered Jun 29, 2016 at 4:53

Jonny Henly

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5 Comments

Juned Over a year ago

Its giving output as -e This is line 1 This is line 2 This is line 3

John Kugelman Over a year ago

@juned You need a version of echo which supports -e. Bash's built-in echo command does, as does GNU's /bin/echo binary.

Juned Over a year ago

No that worked when I ran script with ./script.sh but with sh scripname it ddin't

John Kugelman Over a year ago

Don't run scripts with sh script.sh. It overrides the interpreter the script wants, instead using plain sh. Type ./script.sh to ensure the correct interpreter is used.

Jonny Henly Over a year ago

Hope you don't mind that I added your comment to my answer @mklement0 , feel free to edit it to your liking.

eQ19 · Accepted Answer · 2019-08-12 13:13:48Z

0

You could also store the lines to a variable using read lines:

$ read -r -d '' FOO << EOF
This is line 1
This is line 2
This is line 3
EOF

To see the newline on printing use quotes around the variable: (echo "$FOO" not echo $FOO)

$ echo "$FOO"
This is line 1
This is line 2
This is line 3

answered Aug 12, 2019 at 13:13

eQ19

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