topic Re: comm in Operating System - Linux

comm

Ngoh Chean Siung — Tue, 04 Oct 2005 23:14:27 GMT

Hi,

I hv 2 files called 1 and 2.

Content of 1
============
tls
norainij
abcd
tyt

Content of 2
============
abcd

I want to comm these 2 files and the output that I want is only

tls
norainij
tyt

The command that I use is comm -3 1 2 but the output is as below

abcd
tls
norainij
abcd
tyt

May I know what is the problem?

regards.

Re: comm

RAC_1 — Tue, 04 Oct 2005 23:22:13 GMT

The command should be
comm -23 file1 file2

Read the man page carefully and pay special attention to exmaples section.

Re: comm

Arunvijai_4 — Tue, 04 Oct 2005 23:23:49 GMT

# man comm says,

comm reads file1 and file2, which should be ordered in increasing
collating sequence (see sort(1) and Environment Variables below), and
produces a three-column output:

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

So, you have to sort file1 before doing anything.

Try this,
# sort one >three (Sort one and store it in three)

# comm -23 three two

norainij
tls
tyt

-Arun

Re: comm

Muthukumar_5 — Wed, 05 Oct 2005 01:03:02 GMT

You can use sort + uniq as,

# sort file1 file2 | uniq -u

hth.

Re: comm

Muthukumar_5 — Wed, 05 Oct 2005 01:09:32 GMT

You may not use comm to do this job. It can find common lines based 3 1 2 settings. You can use grep as well as,

# grep -vf file2 file1
tls
norainij
tyt

hth.

Re: comm

Sandman! — Wed, 05 Oct 2005 16:14:03 GMT

comm will do the job as long as the files have been sorted before i.e.

# sort f1 | comm -23 - f2

OR

# sort f1 > f1.out; sort f2 > f2.out; comm -23 f1.out f2.out

regards!