[Linux 常見問題] Getting the count of unique values in a column in bash

 Source From Here

Question
I have tab delimited files with several columns. I want to count the frequency of occurrence of the different values in a column for all the files in a folder and sort them in decreasing order of count (highest count first). How would I accomplish this in a Linux command line environment?

It can use any common command line language like awk, perl, python etc.

HowTo
To see a frequency count for column two (for example):

# awk -F '\t' '{print $2}' * | sort | uniq -c | sort -nr

fileA.txt

view plaincopy to clipboardprint?

1. z    z    a  
2. a    b    c  
3. w    d    e  

fileB.txt

view plaincopy to clipboardprint?

1. t    r    e  
2. z    d    a  
3. a    g    c  

fileC.txt

view plaincopy to clipboardprint?

1. z    r    a  
2. v    d    c  
3. a    m    c  

Result:

view plaincopy to clipboardprint?

1. 3 d  
2. 2 r  
3. 1 z  
4. 1 m  
5. 1 g  
6. 1 b