Sort and uniq columns individually in a text file

sortuniq

I have a file as below:

D F T E
A R T E
K A O E
E T P J

I would like to sort each column and unique the columns individually as below:

A A O E
D F P J
E R T
K T

I wonder if there is anyone who knows how to use sort or uniq to do so?

Best Answer

You can try something like this:

paste -d'\t' <(cut -f 1 -d' ' file | sort -u) <(cut -f 2 -d' ' file | sort -u) <(cut -f 3 -d' ' file | sort -u) <(cut -f 4 -d' ' file | sort -u) >output

I put tab as delimiter of paste to be more visible the output.

Related Solutions

Bash Sort Uniq – Difference Between ‘sort -u’ and ‘sort | uniq’

sort | uniq existed before sort -u, and is compatible with a wider range of systems, although almost all modern systems do support -u -- it's POSIX. It's mostly a throwback to the days when sort -u didn't exist (and people don't tend to change their methods if the way that they know continues to work, just look at ifconfig vs. ip adoption).

The two were likely merged because removing duplicates within a file requires sorting (at least, in the standard case), and is an extremely common use case of sort. It is also faster internally as a result of being able to do both operations at the same time (and due to the fact that it doesn't require IPC between uniq and sort). Especially if the file is big, sort -u will likely use fewer intermediate files to sort the data.

On my system I consistently get results like this:

$ dd if=/dev/urandom of=/dev/shm/file bs=1M count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 8.95208 s, 11.7 MB/s
$ time sort -u /dev/shm/file >/dev/null

real        0m0.500s
user        0m0.767s
sys         0m0.167s
$ time sort /dev/shm/file | uniq >/dev/null

real        0m0.772s
user        0m1.137s
sys         0m0.273s

It also doesn't mask the return code of sort, which may be important (in modern shells there are ways to get this, for example, bash's $PIPESTATUS array, but this wasn't always true).

Sort and Uniq in Awk – How to Use

To sort you can use a pipe also inside of an awk command, as in:

awk '{ print ... | "sort ..." }'

The syntax means that all respective lines of the data file will be passed to the same instance of sort.

Of course you can also do that equivalently on shell level:

awk '{ print ... }' | sort ...

Or you can use GNU awk which has a couple sort functions natively defined.

The uniq is in awk typically accomplished by saving the "unique data element or key" in an associative array and checking whether new data need to be memorized. One example to illustrate:

awk '!a[$0]++'

This means: If the current line is not in the array then the condition is true and the default action to print the line triggered. Subsequent lines with the same data will result in a false condition and the data will not be printed.

Best Answer

Related Solutions

Bash Sort Uniq – Difference Between ‘sort -u’ and ‘sort | uniq’

Sort and Uniq in Awk – How to Use

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