Find duplicate lines in a file and count how many time each line was duplicated?

Question

Suppose I have a file similar to the following:

123 
123 
234 
234 
123 
345

I would like to find how many times '123' was duplicated, how many times '234' was duplicated, etc. So ideally, the output would be like:

123  3 
234  2 
345  1

Bhili

What language do you want to use? – Gambetta

Answer 1

Assuming there is one number per line:

sort <file> | uniq -c

You can use the more verbose --count flag too with the GNU version, e.g., on Linux:

sort <file> | uniq --count

Philipp

This is what I do however algorithmically this is doesnt seem to be the most efficient approach (O(n log n)*avg_line_len where n is number of lines). I'm working on files that are several gigabytes large, so performance is a key issue. I wonder whether there is a tool that does just the counting in a single pass using a prefix tree (in my case strings often have common prefixes) or similar, that should do the trick in O(n) * avg_line_len. Does anyone know such a commandline tool? – Hayman

An additional step is to pipe the output of that into a final 'sort -n' command. That will sort the results by which lines occur most often. – Milissa

If you want to only print duplicate lines, use 'uniq -d' – Cam

If you want to again sort the result, you may use sort again like: sort <file> | uniq -c | sort -n – Andersonandert

if @Cam hat not mentioned -d I would have taken … | uniq -c | grep -v '^\s*1' (-v means inverse regexp, that denies matches (not verbose, not version :)) – Cloakroom

by the way, you can use -c -d and print duplicate lines and the count – Morry

Is there a way to ignore the first part of a text file? My logs have timestamps, so I want to ignore the first n chars. – Sicyon

@Sicyon https://mcmap.net/q/53918/-how-can-i-remove-the-first-line-of-a-text-file-using-bash-sed-script – Sharecropper

Answer 2

This will print duplicate lines only, with counts:

sort FILE | uniq -cd

or, with GNU long options (on Linux):

sort FILE | uniq --count --repeated

on BSD and OSX you have to use grep to filter out unique lines:

sort FILE | uniq -c | grep -v '^ *1 '

For the given example, the result would be:

  3 123
  2 234

---

If you want to print counts for all lines including those that appear only once:

sort FILE | uniq -c

or, with GNU long options (on Linux):

sort FILE | uniq --count

For the given input, the output is:

  3 123
  2 234
  1 345

---

In order to sort the output with the most frequent lines on top, you can do the following (to get all results):

sort FILE | uniq -c | sort -nr

or, to get only duplicate lines, most frequent first:

sort FILE | uniq -cd | sort -nr

on OSX and BSD the final one becomes:

sort FILE | uniq -c | grep -v '^ *1 ' | sort -nr

Willaims

Good point with the --repeated or -d option. So much more accurate than using "|grep 2" or similar! – Mateo

How I can modify this command to retrieve all lines whose repetition count is more than 100 ? – Theodora

@Theodora Adding | sort -n or | sort -nr to the pipe will sort the output by repetition count (ascending or descending respectively). This is not what you're asking but I thought it might help. – Willaims

@Theodora awk seems able to do all kind of calculations: in your case you could do | awk '$1>100' – Willaims

@fionbio sort FILE | uniq -cd should work on OSX too – Willaims

@fionbio Looks like you can't use -c and -d together on OSX uniq. Thanks for pointing out. You can use grep to filter out unique lines: sort FILE | uniq -c | grep -v '^ *1 ' – Willaims

Piping to awk '$1>1' seems a lot better than grep -v '^ *1 ' to me. It allows us to change the minimum duplicate count with ease and works flawlessly even on macOS. :) – Haeres

sort FILE | uniq -c | grep -v '^ *1 ' | sort -nr is beautiful! – Standley

on OSX you can use uniq -d if you don't care about the count – Branton

Answer 3

To find and count duplicate lines in multiple files, you can try the following command:

sort <files> | uniq -c | sort -nr

or:

cat <files> | sort | uniq -c | sort -nr

Northampton

Answer 4

Via awk:

awk '{dups[$1]++} END{for (num in dups) {print num,dups[num]}}' data

In awk 'dups[$1]++' command, the variable $1 holds the entire contents of column1 and square brackets are array access. So, for each 1st column of line in data file, the node of the array named dups is incremented.

And at the end, we are looping over dups array with num as variable and print the saved numbers first then their number of duplicated value by dups[num].

Note that your input file has spaces on end of some lines, if you clear up those, you can use $0 in place of $1 in command above :)

Requisite

Isn't this a bit of overkill considering that we have uniq? – Salian

sort | uniq and the awk solution have quite different performance & resource trade-offs: if the files are large and the number of different lines is small, the awk solution is a lot more efficient. It is linear in the number of lines and the space usage is linear in the number of different lines. OTOH, the awk solution needs to keeps all the different lines in memory, while (GNU) sort can resort to temp files. – Garnettgarnette

Answer 5

In Windows, using "Windows PowerShell", I used the command mentioned below to achieve this

Get-Content .\file.txt | Group-Object | Select Name, Count

Also, we can use the where-object Cmdlet to filter the result

Get-Content .\file.txt | Group-Object | Where-Object { $_.Count -gt 1 } | Select Name, Count

Nancynandor

can you delete all occurrences of the duplicates except the last one...without changing the sort order of the file? – Corenecoreopsis

Similarly to below, you can, of course, also sort, using ...| Sort -Top 15 -Descending Count | Select Name – Test

Answer 6

To find duplicate counts, use this command:

sort filename | uniq -c | awk '{print $2, $1}'

Shovelhead

Answer 7

Assuming you've got access to a standard Unix shell and/or cygwin environment:

tr -s ' ' '\n' < yourfile | sort | uniq -d -c
       ^--space char

Basically: convert all space characters to linebreaks, then sort the tranlsated output and feed that to uniq and count duplicate lines.

Jolin

I guess this solution was tailored to a specific case of your own? i.e. you've got a list of words separated by spaces or newlines only. If it's only a list of numbers separated by newlines (no spaces) it will work fine there, but obviously your solution will treat lines containing spaces differently. – Chlorohydrin