compare two files in UNIX

Question

I would like to compare two files [ unsorted ] file1 and file2. I would like to do file2 - file1 [ the difference ] irrespective of the line number? diff is not working.

Have you considered sorting and then comparing? – Nikolai Fetissov Jan 17 '11 at 17:20 — Nikolai Fetissov, Jan 17 '11 at 17:20
Diff is not working? Diff should work. what's the error? – Neilvert Noval Jan 17 '11 at 17:27 — Neilvert Noval, Jan 17 '11 at 17:27
Not programming... Move to superuser. – leppie Jan 21 '11 at 06:44 — leppie, Jan 21 '11 at 06:44

score 27 · Answer 1 · edited Aug 18 '16 at 09:22

27

Well, you can just sort the files first, and diff the sorted files.

sort file1 > file1.sorted
sort file2 > file2.sorted
diff file1.sorted file2.sorted

You can also filter the output to report lines in file2 which are absent from file1:

diff -u file1.sorted file2.sorted | grep "^+"

As indicated in comments, you in fact do not need to sort the files. Instead, you can use a process substitution and say:

diff <(sort file1) <(sort file2)

edited Aug 18 '16 at 09:22

fedorqui

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answered Jan 17 '11 at 17:23

tonio

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By the way, bash has a shortcut for the first three commands together: `diff <(sort file1) <(sort file2)`. – amalloy May 25 '13 at 03:41

score 27 · Accepted Answer · edited Apr 03 '13 at 14:10

27

I got the solution by using comm

comm -23 file1 file2

will give you the desired output.

The files need to be sorted first anyway.

edited Apr 03 '13 at 14:10

fedorqui

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answered Jan 21 '11 at 06:43

Balualways

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According to [`comm` man page](http://netbsd.gw.com/cgi-bin/man-cgi?comm++NetBSD-current), it works on lexically sorted files. Thus, you will have to use `sort` on your files first. – tonio Feb 09 '11 at 14:33
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Like indicated by [amalloy's comment](http://stackoverflow.com/questions/4715885/compare-two-files-in-unix/4756123#comment24120178_4715952) for `diff`, you can also say `comm -23 <(sort file1) <(sort file2)`. – fedorqui Jul 28 '16 at 08:46

score 4 · Answer 3 · edited Sep 25 '17 at 08:29

4

There are 3 basic commands to compare files in unix:

cmp : This command is used to compare two files byte by byte and as any mismatch occurs,it echoes it on the screen.if no mismatch occurs i gives no response. syntax:$cmp file1 file2.
comm : This command is used to find out the records available in one but not in another
diff

edited Sep 25 '17 at 08:29

Vivek Ji

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answered May 25 '13 at 02:45

vishruti

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to add on top of this, cmp is used only on sorted data. – Alex Raj Kaliamoorthy Apr 20 '16 at 10:49

score 2 · Answer 4 · answered Jan 17 '11 at 17:23

2

Most easy way: sort files with sort(1) and then use diff(1).

answered Jan 17 '11 at 17:23

gelraen

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compare two files in UNIX

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