Diff command with a condition

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1

Hi

I have 2 files test1 & test2.

Test1 contains :
BSC
AFCN

Test2 contains:
AFCN

I than use the following command :

diff file1 file2

which displays than displays : 2d1
< BSC

Basically I want to confirm that except for "BSC", AFCN is the only word in each file.So when I do a "Diff" how do i say do not take "BSC" into consideration but just check for other differences(in this case only AFCN)?

Thanks & Regards
Pragesan

2

Well the most obvious would be to remove the unwanted line before to use diff...
To really help you, we would need to know a bit more:
Is this case always true? (First line unwanted) etc...

3

Hi vbe

Thanks for the reply.

Yes this is always true.File1 i.e Test1 will always contain the first line "BSC" which I don't want.So when i'm doing the diff between the two files I'm hoping to see only 1 difference i.e the word "BSC" but to make it easier for others to read I would like the diff command not to take the first line of Test1 into consideration. and thus have no differences.

I hope this makes sense

Thanks & Regards
Pragesan

4

if you want to compare test1 and test2 but ignore ALL "BSC" from test1:

grep -v 'BSC' test1|diff - test2

if you want to compare test1 and test2 but ignore the 1st line from test1:

sed -n '2,$p' test1|diff - test2
5

Hi sk1418

Thanks for your reply.Both of your commands work.I need the second command :slight_smile:

I'm extremly new to unix.Please could you explain command 2.It will help me a lot going forward.

sed -n '2,$p' test1|diff - test2
Thank you once again.
.

6

sed command will cut the 1st line from your test1 file, and pass the result to diff command via pipe, to compare with test2 file.

7

Since your new at unix, you could have a look at the man pages of tail and head commands, for you could have used e.g.

 tail -n +2 test1

maybe more accessible for a novice than having to assimilate sed (and awk) syntax, nevertheless you would have to use it in the same way as the bright example of sk1418 since diff wants 2 files in input you have to use "-" to say "Standard Input - to be used as file1"...