Is there a way to 'uniq' by column?

user_233071 0
Viewed 217364

I have a .csv file like this:

stack2@domain.example,2009-11-27 01:05:47.893000000,domain.example,127.0.0.1
overflow@domain2.example,2009-11-27 00:58:29.793000000,domain2.example,255.255.255.0
overflow@domain2.example,2009-11-27 00:58:29.646465785,domain2.example,256.255.255.0
...

I have to remove duplicate e-mails (the entire line) from the file (i.e. one of the lines containing overflow@domain2.example in the above example). How do I use uniq on only field 1 (separated by commas)? According to man, uniq doesn't have options for columns.

I tried something with sort | uniq but it doesn't work.

uniq shell sorting linux
8 Answers
sort -u -t, -k1,1 file
  • -u for unique
  • -t, so comma is the delimiter
  • -k1,1 for the key field 1

Test result:

overflow@domain2.example,2009-11-27 00:58:29.793000000,xx3.net,255.255.255.0
stack2@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
user_1722110 
awk -F"," '!_[$1]++' file
  • -F sets the field separator.
  • $1 is the first field.
  • _[val] looks up val in the hash _(a regular variable).
  • ++ increment, and return old value.
  • ! returns logical not.
  • there is an implicit print at the end.
user_1315270

If you want to use uniq:

<mycvs.cvs tr -s ',' ' ' | awk '{print $3" "$2" "$1}' | uniq -c -f2

gives:

1 01:05:47.893000000 2009-11-27 tack2@domain.example
2 00:58:29.793000000 2009-11-27 overflow@domain2.example
1
user_2321440

well, simpler than isolating the column with awk, if you need to remove everything with a certain value for a given file, why not just do grep -v:

e.g. to delete everything with the value "col2" in the second place line: col1,col2,col3,col4

grep -v ',col2,' file > file_minus_offending_lines

If this isn't good enough, because some lines may get improperly stripped by possibly having the matching value show up in a different column, you can do something like this:

awk to isolate the offending column: e.g. 

awk -F, '{print $2 "|" $line}'

the -F sets the field delimited to ",", $2 means column 2, followed by some custom delimiter and then the entire line. You can then filter by removing lines that begin with the offending value:

 awk -F, '{print $2 "|" $line}' | grep -v ^BAD_VALUE

and then strip out the stuff before the delimiter:

awk -F, '{print $2 "|" $line}' | grep -v ^BAD_VALUE | sed 's/.*|//g'

(note -the sed command is sloppy because it doesn't include escaping values. Also the sed pattern should really be something like "[^|]+" (i.e. anything not the delimiter). But hopefully this is clear enough.

user_194790

By sorting the file with sort first, you can then apply uniq.

It seems to sort the file just fine:

$ cat test.csv
overflow@domain2.example,2009-11-27 00:58:29.793000000,xx3.net,255.255.255.0
stack2@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
overflow@domain2.example,2009-11-27 00:58:29.646465785,2x3.net,256.255.255.0
stack2@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack3@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack4@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack2@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1

$ sort test.csv
overflow@domain2.example,2009-11-27 00:58:29.646465785,2x3.net,256.255.255.0
overflow@domain2.example,2009-11-27 00:58:29.793000000,xx3.net,255.255.255.0
stack2@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack2@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack2@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack3@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack4@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1

$ sort test.csv | uniq
overflow@domain2.example,2009-11-27 00:58:29.646465785,2x3.net,256.255.255.0
overflow@domain2.example,2009-11-27 00:58:29.793000000,xx3.net,255.255.255.0
stack2@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack3@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack4@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1

You could also do some AWK magic:

$ awk -F, '{ lines[$1] = $0 } END { for (l in lines) print lines[l] }' test.csv
stack2@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack4@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
stack3@domain.example,2009-11-27 01:05:47.893000000,xx2.net,127.0.0.1
overflow@domain2.example,2009-11-27 00:58:29.646465785,2x3.net,256.255.255.0
user_1412740
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