Bash - remove duplicates without sort

Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Bash - remove duplicates without sort
# 1  
Old 08-31-2013
Bash - remove duplicates without sort

I need to use bash to remove duplicates without using sort first.

I can not use:
cat file | sort | uniq

But when I use only

cat file | uniq

some duplicates are not removed.
# 2  
Old 08-31-2013
Obviously, the simple way to do this is:
sort -u file

but you tell us we can't do that without saying why. Is there a requirement to output lines in the same order they were in in the input file? If so, is it important to keep a particular one of the duplicated lines in the output? Or, do you want every line that had one or more duplicates removed from the output?

In the 2.5 years you've been a member of this forum, there have seen dozens of examples using awk to do this where the 1st duplicated input line is kept or the last duplicated input line is kept, or all duplicated lines are removed. If keeping the same order is important, it is more difficult to keep the last duplicate than it is to keep the 1st duplicate.

So, what are the real requirements?
# 3  
Old 09-01-2013
awk '!a[$0]++' file

# 4  
Old 09-01-2013

Originally Posted by Jotne
awk '!a[$0]++' file

I tried:
echo -e "prova\012zappa\012prova\012quadro\012cesto\012zappa" | awk '!a[$0]++'

and it works Smilie.

Please explain me what does it means:

# 5  
Old 09-01-2013
This User Gave Thanks to Jotne For This Post:
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Concatenate and sort to remove duplicates

Following is the input. 1st and 3rd block are same(block starts here with '*' and ends before blank line) , 2nd and 4th blocks are also the same: cat <file> * Wed Feb 24 2016 Tariq Saeed <> 2.0.7-1.0.7 - add vmcore dump support for ocfs2 * Mon Jun 8 2015 Brian Maly... (4 Replies)
Discussion started by: Paras Pandey
4 Replies

2. UNIX for Beginners Questions & Answers

Sort and remove duplicates in directory based on first 5 columns:

I have /tmp dir with filename as: 010020001_S-FOR-Sort-SYEXC_20160229_2212101.marker 010020001_S-FOR-Sort-SYEXC_20160229_2212102.marker 010020001-S-XOR-Sort-SYEXC_20160229_2212104.marker 010020001-S-XOR-Sort-SYEXC_20160229_2212105.marker 010020001_S-ZOR-Sort-SYEXC_20160229_2212106.marker... (4 Replies)
Discussion started by: gnnsprapa
4 Replies

3. Shell Programming and Scripting

Sort and Remove duplicates

Here is my task : I need to sort two input files and remove duplicates in the output files : Sort by 13 characters from 97 Ascending Sort by 1 characters from 96 Ascending If duplicates are found retain the first value in the file the input files are variable length, convert... (4 Replies)
Discussion started by: ysvsr1
4 Replies

4. Shell Programming and Scripting

Sort data by date first and then remove duplicates

Hi , I have below data inside a file named ref.psv . I want to create a shell script which will do the below 2 points : (1) sort the file content first based on the latest date which is the last column in the file (actual file its the 175th column) (2)after sorting the file based on latest date... (3 Replies)
Discussion started by: samrat dutta
3 Replies

5. Shell Programming and Scripting

bash - remove duplicates

I need to use a bash script to remove duplicate files from a download list, but I cannot use uniq because the urls are different. I need to go from this: http://***/fae78fe/file1.wmv http://***/39du7si/file1.wmv http://***/d8el2hd/file2.wmv http://***/h893js3/file2.wmv to this: ... (2 Replies)
Discussion started by: locoroco
2 Replies

6. Shell Programming and Scripting

remove duplicates and sort

Hi, I'm using the below command to sort and remove duplicates in a file. But, i need to make this applied to the same file instead of directing it to another. Thanks (6 Replies)
Discussion started by: dvah
6 Replies

7. Shell Programming and Scripting

bash ps; remove the header, sort and reinsert

Hi, I'm ssh'ing into a server using ruby and sending a one-liner to retrieve the output of the 'ps aux' command. So far, this is what I have: ps aux | sort -r -n -k3 | sed -e '1s/^/this is first\n/' | head -n10 With this I can insert a line at position 1, but I would rather extract the... (3 Replies)
Discussion started by: gekeha
3 Replies

8. UNIX for Dummies Questions & Answers

removing duplicates and sort -k

Hello experts, I am trying to remove all lines in a csv file where the 2nd columns is a duplicate. I am try to use sort with the key parameter sort -u -k 2,2 File.csv > Output.csv File.csv File Name|Document Name|Document Title|Organization Word Doc 1.doc|Word Document|Sample... (3 Replies)
Discussion started by: orahi001
3 Replies

9. Shell Programming and Scripting

Sort, Uniq, Duplicates

Input File is : ------------- 25060008,0040,03, 25136437,0030,03, 25069457,0040,02, 80303438,0014,03,1st 80321837,0009,03,1st 80321977,0009,03,1st 80341345,0007,03,1st 84176527,0047,03,1st 84176527,0047,03, 20000735,0018,03,1st 25060008,0040,03, I am using the following in the script... (5 Replies)
Discussion started by: Amruta Pitkar
5 Replies

10. Shell Programming and Scripting

Removing duplicates [sort , uniq]

Hey Guys, I have file which looks like this, Contig201#numbPA Contig1452#nmdynD6PA dm022p15.r#CG6461PA dm005e16.f#SpatPA IGU001_0015_A06.f#CG17593PA I need to remove duplicates based on the chracter matching upto '#'. for example if we consider this.. Contig201#numbPA... (4 Replies)
Discussion started by: sharatz83
4 Replies
Login or Register to Ask a Question