Bash - convert array to lines (for using sort & uniq)

Question

let's say I have an array that goes like this (a a b b b c c d) I want the array to have only one each character/string (a b c d) is there any way converting the array into lines so I can use sort & uniq without temp file?

thanks !

possible duplicate of [How can I get unique values from an array in linux bash?](http://stackoverflow.com/questions/13648410/how-can-i-get-unique-values-from-an-array-in-linux-bash) — dsemi, Aug 12 '14 at 18:53

chepner · Answer 1 · 2014-08-12T18:57:33.973

5

You can use the printf command.

printf "%s\n" "${array[@]}" | sort | uniq

This will print each element of array followed by a newline to standard output.

To repopulate the array, you might use

readarray -t array < <(printf "%s\n" "${array[@]}" | sort | uniq)

However, you might instead simply use an associative array to filter out the duplicates.

declare -A aa
for x in "${array[@]}"; do
    aa[$x]=1
done
array=()
for x in "${!aa[@]}"; do
    array+=("$x")
done

edited Aug 12 '14 at 18:57

answered Aug 12 '14 at 18:51

chepner

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2

You can also combine the `... | sort | uniq` into `... | sort -u` – Keith Thompson Aug 12 '14 at 19:02
2

Or `array=("${!aa[@]}")`. – konsolebox Aug 12 '14 at 19:25
Why on earth did I write that second `for` loop? – chepner Aug 12 '14 at 19:32

score 1 · Accepted Answer · answered Aug 12 '14 at 19:21

1

As a curiosity, the:

arr=(a a b b b c c d)
echo "${arr[@]}" | xargs -n1 | sort -u

prints

a
b
c
d

and the

echo "${arr[@]}" | xargs -n1 | sort -u | xargs

prints

a b c d

answered Aug 12 '14 at 19:21

clt60

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score -2 · Answer 3 · answered Aug 12 '14 at 18:52

-2

 for x in a a b b b c c d; do echo -e $x; done | sort | uniq

answered Aug 12 '14 at 18:52

leogtzr

480
4
7

Bash - convert array to lines (for using sort & uniq)

3 Answers3