How to split a multi-line string containing the characters "\n" into an array of strings in bash? [duplicate]

Question

I have a string in the following format:

I'm\nNed\nNederlander
I'm\nLucky\nDay
I'm\nDusty\nBottoms

I would like to move this to an array of strings line by line such that:

$ echo "${ARRAY[0]}"
I'm\nNed\nNederlander

$ echo "${ARRAY[1]}"
I'm\nLucky\nDay

$ echo "${ARRAY[2]}"
I'm\nDusty\nBottoms

However, I'm running into problems with the "\n" characters within the string itself. They are represented in the string as two separate characters, the backslash and the 'n', but when I try to do the array split they get interpreted as newlines. Thus typical string splitting with IFS does not work.

For example:

$ read -a ARRAY <<< "$STRING"
$ echo "${#ARRAY[@]}"   # print number of elements
2

$ echo "${ARRAY[0]}"
I'mnNednNederla

$ echo "${ARRAY[1]}"
der

BTW, does anybody know how to fix SE's terrible formatting of the code above? — Cory Klein
– Cory Klein, Commented Jul 31, 2012 at 17:51
The "terrible formatting" is due to the apostrophes being interpreted as single quotes (which it expects to be balanced). Use the "block quote" tags instead of "code" tags. — twalberg
– twalberg, Commented Jul 31, 2012 at 17:59

jordanm · Accepted Answer · 2012-07-31 17:56:13Z

41

By default, the read builtin allows \ to escape characters. To turn off this behavior, use the -r option. It is not often you will find a case where you do not want to use -r.

string="I'm\nNed\nNederlander
I'm\nLucky\nDay
I'm\nDusty\nBottoms"

arr=()
while read -r line; do
   arr+=("$line")
done <<< "$string"

In order to do this in one-line (like you were attempting with read -a), actually requires mapfile in bash v4 or higher:

mapfile -t arr <<< "$string"

answered Jul 31, 2012 at 17:56

jordanm

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1 Comment

electronix384128 Over a year ago

yeah for mapfile oneliner :)

chepner · Accepted Answer · 2012-08-23 02:06:01Z

17

mapfile is more elegant, but it is possible to do this in one (ugly) line with read (useful if you're using a version of bash older than 4):

IFS=$'\n' read -d '' -r -a arr <<< "$string"

answered Aug 23, 2012 at 2:06

chepner

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2 Comments

Vic Seedoubleyew Over a year ago

Indeed, and -d option seems crucial to make it work

chepner Over a year ago

One caveat I did not know about when I posted this: the exit status will be non-zero, since a here string will never end with a null character like read -d '' will expect.

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