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  #1 (permalink)  
Old 04-25-2008
nixguy nixguy is offline
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Posts: 3
duplicate line in a text file

i would like to scan file in for duplicate lines, and print the duplicates to another file,
oh and it has to be case insensitive.

example

line1
line2
line2
line3
line4
line4

outputfile:
line2
line4

any ideas
  #2 (permalink)  
Old 04-25-2008
era era is offline Forum Advisor  
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Join Date: Mar 2008
Location: /there/is/only/bin/sh
Posts: 3,652
Code:
perl -ne '$l = lc(); print if $m{$l}++; ' file
lc returns the specified string in lowercase; in this case, with no parameter, it defaults to the current input line. $m{$l} is the count of number of times we have seen $l; if it's nonzero, it's a duplicate, so we print it.

Last edited by era; 04-25-2008 at 01:50 PM.. Reason: Add explanation
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Old 04-25-2008
nixguy nixguy is offline
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Quote:
Originally Posted by era View Post
Code:
perl -ne '$l = lc(); print if $m{$l}++; ' file
lc returns the specified string in lowercase; in this case, with no parameter, it defaults to the current input line. $m{$l} is the count of number of times we have seen $l; if it's nonzero, it's a duplicate, so we print it.

thanks it's worked for one file, but i forgot to add that if i need it to run on a directory and make sure to do in on a file only and not subdirectory

what modifications would you do
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Old 04-25-2008
era era is offline Forum Advisor  
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Loop over files in a directory, and remove duplicates? Do you want to replace the files?

Code:
for f in directory/*; do
  test -d "$f" && continue   # skip if it's a subdirectory
  perl -ne '$l = lc(); print if $m{$l}++; ' "$f" >"$f.tmp"
  mv "$f.tmp" "$f"
done
  #5 (permalink)  
Old 04-25-2008
nixguy nixguy is offline
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Posts: 3
Thank you Era, it worked,
  #6 (permalink)  
Old 04-29-2008
summer_cherry summer_cherry is online now Forum Advisor  
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Join Date: Jun 2007
Location: Beijing China
Posts: 1,049
Code:
awk '{
  a[$0]++
}
END{
 for (i in a)
 if (a[i]=2)
 print i
}' filename
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