sortuniq provides optimised versions of various
| sort | uniq
constructions which are common in shell scripting. This construction
finds all the unique lines in an input, regardless of the line order.
1 2 3 2 1
1 2 3
| sortuniq generates the same set of results
| sort | uniq, and produces them immediately. This is, uh,
slightly disconcerting. They are not sorted, unlike in the original.
| sortuniq -c generates the similar output to
| sort | uniq -c.
| sortuniq --local will drop "local" duplicates from a stream, again
immediately. This can be useful if your data is very large, and has many
useless values in, and you only want the eventual
uniq values, or some
other idea of the stream. For example, for some data which looks like:
one two ponies! two one one horses! two one ponies!
| sortuniq --local --size-hint 3 will (immediately) print:
one two ponies! horses! ponies!
It has eliminated many of the
two entries, but can't
eliminate the second
ponies! as it runs out of "memory". You can
(arbitrarily) increase the
You can't really do that with
uniq, which can't look more than
one line back in the history.
I took a gigabyte of rendered Wikipedia pages, and extracted the "words", giving >200 million lines.
For this input:
| sortuniq -ctakes 17.5s (single core) and 190MB of memory (max RSS)
| sort | uniq -ctakes 111s (405s total user time) and around 4gb of memory.
That's a 6x-23x speedup, and a 21x memory improvement.
Here's a subset of the input (via. wikiextractor
| perl -pe 's/\b/\n/g;s/[ \t]//g' | egrep -v '^$':
Helena Carroll Helena Winifred Carroll ( 13 November 1928 – 31 March 2013 ) was a veteran film , television and stage actress .
The most common words are, unsurprisingly:
1195445 by 1229458 with 1274390 on 1360706 as 1405234 for 1416371 ' 1675168 is 1777549 The 1931603 - 2074956 was 3038885 " 3462954 a 3630791 to 4267812 in 4999315 and 5732322 of 8336207 . 9153796 , 10748102 the