How do I grep something and prevent the phrase appearing in the results?

Question

I am trying to get only the MAC address from multiple systems and want only the MAC address in the results.

ipmitool lan print | grep "MAC Address             : "
# => MAC Address             : aa:bb:cc:dd:ee:ff

I got as far using google as trying is by adding -oP and \K\w+ but for some reason it only get's the first 2 digits of the MAC:

ipmitool lan print | grep -oP "MAC Address             : \K\w+"
# => aa

I understand the -o will only show the matched text which is why the MAC address is not being shown up and -P used with \K will prevent everything in-between from showing up but not sure what exactly to put after \w+ to make the rest of the MAC address show up.

Wiktor Stribiżew can you post it as a answer so I can mark it as answered? — Andy, Oct 08 '20 at 22:54
Albeit https://stackoverflow.com/a/62840426/11329890 looks like an answer, its `.*` can go much farther than a single word, and MAC address is a single word. This post looks useful, with a better explanation of the pattern. — Ryszard Czech, Oct 09 '20 at 19:59

Wiktor Stribiżew · Accepted Answer · 2020-10-09T10:31:45.063

0

You can match it with

grep -oP 'MAC Address : \K\S+' file

Here,

-o - extracts the matched texts, not whole lines
P - enables the PCRE regex syntax
MAC Address : - matches a literal text
\K - match reset operator that discards the text matched so far from the memory match buffer
\S+ - one or more non-whitespace chars.

edited Oct 09 '20 at 10:31

answered Oct 09 '20 at 00:17

Wiktor Stribiżew

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`grep -P` is not portable, though. The traditional solution would be `sed -n 's/.*MAC Address : //p'` or perhaps `sed -n 's/.*MAC Address : \([0-9a-fA-F:]*\).*/\1/p'` if there may be text after the match which should not be printed. – tripleee Oct 09 '20 at 09:40
1

@tripleee That is all good, just note the answer is meant to address the immediate issue without forcing OP to change the tool set used. I myself do not need any alternative if I am used to a specific tool. In this case, I'd also use `grep` with `-P` since I am a regular Ubuntu Linux user and an NFA regex fan. If OP were interested in `sed` solution, I'd have added it to the answer. – Wiktor Stribiżew Oct 09 '20 at 10:22
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Sure, just commenting for future visitors. Perhaps this should be closed as a duplicate of an existing question anyhow, where then hopefully portability of answers would be at least broadly documented. – tripleee Oct 09 '20 at 10:27

How do I grep something and prevent the phrase appearing in the results?

1 Answers1