I've got almost the same question as here.
I have an array which contains aa ab aa ac aa ad
, etc.
Now I want to select all unique elements from this array.
Thought, this would be simple with sort | uniq
or with sort -u
as they mentioned in that other question, but nothing changed in the array...
The code is:
echo `echo "${ids[@]}" | sort | uniq`
What am I doing wrong?
A bit hacky, but this should do it:
echo "${ids[@]}" | tr ' ' '\n' | sort -u | tr '\n' ' '
To save the sorted unique results back into an array, do Array assignment:
sorted_unique_ids=($(echo "${ids[@]}" | tr ' ' '\n' | sort -u | tr '\n' ' '))
If your shell supports herestrings (bash
should), you can spare an echo
process by altering it to:
tr ' ' '\n' <<< "${ids[@]}" | sort -u | tr '\n' ' '
Input:
ids=(aa ab aa ac aa ad)
Output:
aa ab ac ad
Explanation:
"${ids[@]}"
- Syntax for working with shell arrays, whether used as part of echo
or a herestring. The @
part means "all elements in the array"tr ' ' '\n'
- Convert all spaces to newlines. Because your array is seen by shell as elements on a single line, separated by spaces; and because sort expects input to be on separate lines.sort -u
- sort and retain only unique elementstr '\n' ' '
- convert the newlines we added in earlier back to spaces.$(...)
- Command Substitutiontr ' ' '\n' <<< "${ids[@]}"
is a more efficient way of doing: echo "${ids[@]}" | tr ' ' '\n'