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uniq without pre-sorting

Terminal - uniq without pre-sorting
perl -ne 'print if !$a{$_}++'
2011-02-17 02:18:44
User: doherty
Functions: perl
3
uniq without pre-sorting

Reads stdin, and outputs each line only once - without sorting ahead of time. This does use more memory than your system's sort utility.

Alternatives

There is 1 alternative - vote for the best!

Terminal - Alternatives
awk '!x[$0]++' <file>
2009-12-20 02:33:21
User: din7
Functions: awk
71

Using awk, find duplicates in a file without sorting, which reorders the contents. awk will not reorder them, and still find and remove duplicates which you can then redirect into another file.

export PATH=`echo -n $PATH | awk -v RS=":" '{ if (!x[$0]++) {printf s $0; s=":"} }'`
awk '!NF || !seen[$0]++'
2015-02-25 17:03:13
User: Soubsoub
Functions: awk
1

Remove duplicate lines whilst keeping order and empty lines

glu() { (local IFS="$1"; shift && echo "$*") }; repath() { ( _E=`echo "${PATH//:/$'\n'}" | awk '!x[$0]++'`; glu ":" $_E ) ; } ; PATH=`repath` ; export PATH
2011-06-09 12:11:18
User: Timothy
Functions: awk echo export shift
0

Thanks to the authors of:

awk '!x[$0]++' <file>

and the author of:

joinargs() { (local IFS="$1"; shift && echo "$*") }

and others, we can have a fast Linux or android.

IMPORTANT if you find a priority order problem in PATH you can push a path directory to the front without duplication as follows:

PATH=/bin:$PATH

then ...

Check duplication with:

echo $PATH|tr : '\n'|sort|uniq -d

Finally do a very neat line by line list of $PATH:

echo "${PATH//:/$'\n'}

The speed up is very noticeable for android, and builds on Linux Ubantu are much faster with make and scripts.

I will update the command on request. Timothy from SONY

Know a better way?

If you can do better, submit your command here.

What others think

Sure, but it has to be understood that this approach uses a lot of memory.

Comment by depesz 302 weeks and 4 days ago

+1

though, another pipe line is another fork which duplicates the entire process memory.

Comment by RanyAlbeg 302 weeks and 3 days ago

Your point of view

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