12
votes
2answers
503 views

How does awk '!a[$0]++' work?

This one-liner removes duplicate lines from text input without pre-sorting. For example: $ cat >f q w e w r $ awk '!a[$0]++' <f q w e r $ The original code I have found on the internets ...
2
votes
2answers
83 views

Removing lines with a single common field

I have a tab separated file that looks like this: 123 some text 123 some different text 334 some other text 341 more text and I want to do two things. One is to order everything numerically ...
3
votes
1answer
255 views

Fastest `uniq` tool in linux

I have large text file (1.5 G), I want to know what the fastest and more reliable tool in linux is. I usualy use: awk '!x[$0]++' file.txt But when I use htop command I see my memory usage is ...
2
votes
2answers
88 views

Check if a drive has been Zeroed with xxd and uniq?

I'm looking for a way to check if the entire binary contents of a USB device are purely 0s. I'm trying this command: sudo xxd /dev/sdb | uniq but it has no output and just runs forever. I've ...
2
votes
3answers
307 views

How can I get the last line number of unique commands when grepping my history file?

I rely on my history file for previous commands, especially ones that are long with many parameters. Once I find the command and its line number(nn) I use !nn to run it. I prefer to see the full ...
2
votes
1answer
86 views

Sort doesn't use natural order

I have used uniq -c and sort extensively on other machines, and it always worked very well. Now, on my new Ubuntu (13.04) machine, I end up with a weird ordering: % cat queries.log | grep INSERT | ...
23
votes
3answers
9k views

What is the difference between “sort -u” and “sort | uniq”?

Everywhere I see someone needing to get a sorted, unique list, they always pipe to sort | uniq. I've never seen any examples where someone uses sort -u instead. Why not? What's the difference, and why ...
1
vote
1answer
1k views

How to match 2 large file and print the difference in shell script

I have 2 files. File1 has 400k numerical records. e.g: 1 2 3 4 5 6 .. and so on File 2 also has 420k numerical records. e.g: 1 2 3 4 6 .. and so on Both these file are in unsorted manner. I want ...
4
votes
1answer
270 views

Why is uniq ignoring Unicode and lines with a single letter?

I'm trying to combine both the American and British dictionaries into one large dictionaries, and I'm trying to remove all the duplicates from the superset, but it seems that uniq is not outputting ...
3
votes
1answer
3k views

The simplest method to count lines matching specific patterns, including '0' if line is not found?

I have very big logs (several gigabytes per day), that can (but do not need to) contain specific lines. I have to count the number of occurences of every one of these lines on a daily basis. I have a ...
10
votes
3answers
3k views

How can I remove duplicates in my .bash_history, preserving order?

I really enjoying using control+r to recursively search my command history. I've found a few good options I like to use with it: # ignore duplicate commands, ignore commands starting with a space ...
4
votes
3answers
4k views

Get lines with maximum values in the column using awk, uniq and sort

I have a file with next format 2011-12-01 user1 access1 2011-12-01 user1 access2 2011-12-01 user2 access2 2011-12-01 user4 access2 2011-12-02 user1 access1 2012-01-01 user3 access1 2012-01-01 user4 ...
11
votes
5answers
4k views

case-insensitive search of duplicate file-names

I there a way to find all files in a directory with duplicate filenames, regardless of the casing (upper-case and/or lower-case)?
4
votes
2answers
1k views

Where has my `uniq` or `sort -u` line gone, with some unicode characters

What is going on in the following code snippet? I'm not getting my expected output. I'd think it was a bug, but it happens for 2 different programs (uniq and sort), so I suspect it is something ...