Select unique or distinct values from a list in UNIX shell script

Question

I have a ksh script that returns a long list of values, newline separated, and I want to see only the unique/distinct values. It is possible to do this?

For example, say my output is file suffixes in a directory:

tar
gz
java
gz
java
tar
class
class

I want to see a list like:

tar
gz
java
class

Answer 1

You might want to look at the uniq and sort applications.

./yourscript.ksh | sort | uniq

(FYI, yes, the sort is necessary in this command line, uniq only strips duplicate lines that are immediately after each other)

EDIT:

Contrary to what has been posted by Aaron Digulla in relation to uniq's commandline options:

Given the following input:

class
jar
jar
jar
bin
bin
java

uniq will output all lines exactly once:

class
jar
bin
java

uniq -d will output all lines that appear more than once, and it will print them once:

jar
bin

uniq -u will output all lines that appear exactly once, and it will print them once:

class
java

Answer 2

Pipe them through sort and "uniq". This removes all duplicates.

"uniq -d" gives only the duplicates, "uniq -u" gives only the unique ones (strips single items).

Answer 3

For larger data sets where sorting may not be desirable, you can also use the following perl script:

./yourscript.ksh | perl -ne 'if (!defined $x{$_}) { print $_; $x{$_} = 1; }'

This basically just remembers every line output so that it doesn't output it again.

It has the advantage over the "sort | uniq" solution in that there's no sorting required up front.

Answer 4

With zsh you can do this:

zsh-4.3.9[t]% cat file
tar
gz
java
gz
java
tar
class
class
zsh-4.3.9[t]% u=($(<file)) 
zsh-4.3.9[t]% print -l ${(u)u[@]}
tar
gz
java
class

Or you can use AWK:

zsh-4.3.9[t]% awk '!_[$0]++' file    
tar
gz
java
class

Answer 5

./script.sh | sort -u

This is the same as monoxide's answer, but a little less verbose.