Command opposite to diff

[Sailesh_1]

Hey folks,

I'm looking for a unix (hpux 11.00) command that does just reverse of diff command. instead of showing lines that are different, I want it to show lines that are the same.

can someone tell me please!!

Thanks,
Sailesh

[Geoff Wild · Accepted solution]

Yes - cmp

man cmp

Rgds...Geoff

[Robert Kerr]

Depending on your specific task... try the manpage on cmp and comm?

[Sridhar Bhaskarla]

Hi Sailesh,

'comm' is the one you are looking for. Look at the man page of comm. You are interested in -3 option which is "Lines that appear in both files".

-Sri

[john korterman]

Hi,
perhaps the comm command could be useful...

regards,
John K.

[Sailesh_1]

Thanks to you all who responded..That's what I'm looking for.

Sailesh

[Jeff Schussele]

Hi Sailesh,

Although I always use comm, it should be noted that
sdiff -l file1 file2
will show only identical lines on the left side of output.
and
sdiff file1 file2
will outpout lines w/o a "|", "<" or ">" that are identical.
and finally
sdiff -o file.out file1 file2
will print identical lines unaltered but will prompt for action on diffs.

Rgds,
Jeff

[Pete Randall]

I always though it should be "comm -3" but I learned otherwise in a thread last week:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=388167

It's actually "comm -12" - try it!


Pete

[H.Merijn Brand (procura]

Shridar, it's reverse

-1 don't show lines only in file 1
-2 don't show lines only in file 2
-3 don't show lines in both files

comm is the command, but the option is not -3, but -12

And please also read thread http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=388167 where the same question is answwred in more depth, and I also post what differs between comm, and the perl and sed solution that also work on unsorted files:

perl -e'$f=pop;%l=map{$_=>1}<>;@ARGV=($f);for(<>){exists$l{$_}and print}' fileA fileB

Enjoy, Have FUN! H.Merijn

[Sridhar Bhaskarla]

Hi Sailesh,

Pete is correct. comm -12 will display the common lines provided the files are sorted. So, you will need to create two temporary files and then use comm against them.

Comm with -3 suppresses column 3. So, you would use

comm file1 file2 |awk '{print $3}'

to get the result which is as same as comm -12

Key is that the files are to be sorted.

-Sri

[Sridhar Bhaskarla]

Gotcha Merijn - How deceiving a man page can be?

In fact it is a mere context miss

Column 1: Lines that appear only in file1,
Column 2: Lines that appear only in file2,
Column 3: Lines that appear in both files.

Where the context is "comm produces a three column output".

-Sri

[H.Merijn Brand (procura]

but the nag is that the columns do NOT evenly distribute. Your awk solution is very void:

Try below yourself, because the forum strips whitespace!

lt09:/home/merijn 101 > cat >x0
aa
bb
dd
ff
gg
hh
lt09:/home/merijn 102 > cat >x1
aa
cc
ff
hh
lt09:/home/merijn 103 > comm x0 x1
aa
bb
cc
dd
ff
gg
hh
lt09:/home/merijn 104 >


And now with duplicate lines (still sorted!)

lt09:/home/merijn 104 > cat > x0
aa
bb
dd
ff
ff
gg
hh
lt09:/home/merijn 105 > cat >x1
aa
cc
ff
hh
hh
lt09:/home/merijn 106 > comm x0 x1
aa
bb
cc
dd
ff
ff
gg
hh
hh
lt09:/home/merijn 107 > perl -e'$f=pop;%l=map{$_=>1}<>;@ARGV=($f);for(<>){exists$l{$_}and print}' x0 x1
aa
ff
hh
hh
lt09:/home/merijn 108 > lt09:/home/merijn 108 > perl -e'$f=pop;%l=map{$_=>1}<>;@ARGV=($f);for(<>){exists$l{$_}and print}' x1 x0
aa
ff
ff
hh
lt09:/home/merijn 109 >

Hope this sheds some light

Enjoy, Have FUN! H.Merijn

[Sridhar Bhaskarla]

Well - I wish HP could replace it's comm command with your perl script :-)

grep -f file1 file2

If we want a simple solution. No sorting is needed.

-Sri

[H.Merijn Brand (procura]

No won't work. See other thread

what if file1 has wildcards?

# cat >file1
.*
# cat >file2
aa
bb
# grep -f file1 file2
aa
bb
# grep -f file2 file1
#

as also from the other thread one uses GNU grep, it might work:

# grep -xFf file1 file2

but not all of us are so lucky to have taken the time to have HP's grep replaced with GNU grep

Enjoy, Have FUN! H.Merijn

[Sridhar Bhaskarla]

That's a great show Merijn. Thanks. Ofcourse Enjoyed and had fun.

-Sri