CODEWITHSUNDEEP
bashgrep
Vishnu
Vishnu

Reputation: 220

grep exact pattern from a file in bash

I have the following IP addresses in a file

3.3.3.1
3.3.3.11
3.3.3.111

I am using this file as input file to another program. In that program it will grep each IP address. But when I grep the contents I am getting some wrong outputs.

like

cat testfile | grep -o 3.3.3.1

but I am getting output like

3.3.3.1
3.3.3.1
3.3.3.1

I just want to get the exact output. How can I do that with grep?

Upvotes: 2

Views: 787

Answers (3)

Avinash Raj
Avinash Raj

Reputation: 174874

You may use anhcors.

grep '^3\.3\.3\.1$' file

Since by default grep uses regex, you need to escape the dots in-order to make grep to match literal dot character.

Upvotes: 0

hek2mgl
hek2mgl

Reputation: 158280

Use the following command:

grep -owF "3.3.3.1" tesfile

-o returns the match only and not the whole line.-w greps for whole words, meaning the match must be enclosed in non word chars like <space>, <tab>, ,, ; the start or the end of the line etc. It prevents grep from matching 3.3.3.1 out of 3.3.3.111.

-F greps for fixed strings instead of patterns. This prevents the . in the IP address to be interpreted as any char, meaning grep will not match 3a3b3c1 (or something like this).

Upvotes: 4

Eugeniu Rosca
Eugeniu Rosca

Reputation: 5315

To match whole words only, use grep -ow 3.3.3.1 testfile

UPDATE: Use the solution provided by hek2mgl as it is more robust.

Upvotes: 1

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