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delete duplicate lines from a file and keep the order of the other lines

Terminal - delete duplicate lines from a file and keep the order of the other lines
cat -n <file> | sort -k 2 | uniq -f 1 | sort -n | cut -f 2-
2010-01-21 18:55:58
User: fpunktk
Functions: cat cut sort uniq
4
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delete duplicate lines from a file and keep the order of the other lines

i wanted to delete all duplicate lines from .bash_history and keep the order of the other lines.

the command cat's the file and adds line numbers, then sorts by the second column. afterwards uniq omits repeated lines, but skips the first field (the line number). then it sorts by the line numbers and at the end cuts the numbers off.

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Alternatives

There are 2 alternatives - vote for the best!

Terminal - Alternatives

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What others think

The first chain of commands will work better than second proposal (awk) for the bigger files. I've tested it on the file with 3000000 lines (1000000 unique lines) and awk was 6 times slower (and consumed more memory).

awk will be faster for a smaller files tho.

Comment by zabuch 174 weeks ago

with this code, how would you keep duplicates ONLY and Delete the rest?

Comment by y2j164 155 weeks and 3 days ago

to delete single lines and keep one of each duplicate line, just add the -d option to uniq. e.g.

cat -n <file> | sort -k 2 | uniq -f 1 -d | sort -n | cut -f 2-
Comment by fpunktk 153 weeks and 3 days ago

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