Question

18

Unique sorting: Redirect output to the same file

rated 0 times [ 18] [ 0] / answers: 1 / hits: 17015 / 1 Year ago, fri, january 13, 2023, 7:03:18

Is there any short way to save the pipe output to the same file that it's processed. For example, this is what I am actually doing

$ cat filename | sort | uniq > result

$ rm -f filename

$ mv result filename

I was wondering if there was a way to do it in just one line (not appending those commands using &&)

This is not the way, but to get an idea

$ cat filename | sort | uniq > filename

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arbaour

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1 Year ago

answered 1 Year ago tiowift · Accepted Answer

You can use sponge from moreutils package:

LC_ALL=C sort -u filename | sponge filename

You also don't need pipe to uniq, since when sort has -u option to unique lines when sorting.

Note that on GNU system with UTF-8 locales, sort -u or sort | uniq didn't give you unique lines, but the first from sequence of lines which sort the same in current locale.

$ printf '%b

' 'U2460' 'U2461' | LC_ALL=en_US.utf8 sort | LC_ALL=en_US.utf8 uniq

①

gave you only ①. Changing locale to C force the sorting order based on the byte values:

$ export LC_ALL=C

$ printf '%b

' 'U2460' 'U2461' | LC_ALL=C sort | LC_ALL=C uniq

①

②