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If I have a list in bash

L="11 22 11 33 22 44"

Is there a clean way to get to "11 22 33 44" ?

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2 Answers 2

up vote 3 down vote accepted

One way:

$ L="11 22 11 33 22 44"
$ L=$(echo $L | tr ' ' '\n' | sort -nu)    
$ echo $L
11 22 33 44

Using tr, the numbers are split to individual lines, and sort is used to sort the numbers(-n) and remove the duplicate ones(-u).

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You can leave off the | xargs. Because of the way the shell handles multi-line output from a $(…) command, L=$(echo $L | tr ' ' '\n' | sort –u) is enough. –  Scott Dec 1 '12 at 1:42
@Scott : thanks scott for pointing it out, updated the solution.... –  Guru Dec 1 '12 at 1:45
Clean and easy. 'tr' was the the part I was missing. –  Travis Bear Dec 1 '12 at 1:49

A common pattern in some other programming languages is to store each value as a 'key' in a hash or dictionary or associative array, and rely on the implementation to keep hash keys unique.

declare -A items=()
for item in $L; do

(Unfortunately, the bash implementation is about 2× slower than sort -u.)

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+1..its always a pleasure looking at pure shell solutions.. –  Guru Dec 1 '12 at 2:04

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