CODEWITHSUNDEEP
linuxbashshellgrepifconfig
Jobs
Jobs

Reputation: 3377

Only get the first part of grep: get ip of ifconfig

ifconfig | grep -m1 "inet addr"

Gives me

inet addr:172.30.1.6  Bcast:172.30.140.255  Mask:255.255.252.0

However, I only want the ip, which is 172.30.1.6. How can I do this? Note that I have to be using ifconfig, as this is an embedded system with limited functionalities.

Upvotes: 1

Views: 1549

Answers (8)

James Brown
James Brown

Reputation: 37404

Using Bash's regex operator =~:

$ [[ $(ifconfig | grep -m1 "inet addr") =~ [0-9]+\.[0-9]+\.[0-9]+\.[0-9]+ ]] && echo ${BASH_REMATCH[0]}
172.30.1.6

Update: Something even better in the comments.

Upvotes: 1

Mike Holt
Mike Holt

Reputation: 4612

Here's a way to do it with a single sed command, eliminating the call to grep:

ifconfig | sed -n '/inet addr/{s/^.*inet addr:\([^ ]*\).*$/\1/p;q}'

There are a few things going on here:

  • sed -n tells sed not to print every line like it normally does
  • /inet addr/ is a sed address - it tells sed to only operate on lines containing "inet addr"
  • The { and } brackets define a block of commands to be run, with the commands separated by a ;
  • The s command is fairly straightforward - it just captures the IP and replaces the whole line with just the IP
  • The p flag at the end of the s command tells sed to print the result of the substitution. This is necessary because we called sed with the -n option.
  • The q command tells sed to quit, so that it only processes the first line containing "inet addr".

Using the -n option, the /inet addr/ address, the p flag on the s command, and the q command, essentially has the same effect as grep -m1 "inet addr", which makes calling grep unnecessary. In fact, it's worth noting that the following commands produce identical output:

> ifconfig | grep -m1 "inet addr"
         inet addr:192.168.1.1  Bcast:192.168.2.255  Mask:255.255.255.0

> ifconfig | sed -n '/inet addr/{p;q}'
         inet addr:192.168.1.1  Bcast:192.168.2.255  Mask:255.255.255.0

Here, I've omitted the s/pattern/replacement/p part of the sed command, and replaced it with a p command (which just prints the whole line), just to show the effect of the other parts in isolation.

Upvotes: 2

Ed Morton
Ed Morton

Reputation: 203597

Is this all you're trying to do?

awk -F'[: ]' '/inet addr/{print $3; exit}'

For example using cat file in place of ifconfig:

$ cat file
inet addr:172.30.1.6  Bcast:172.30.140.255  Mask:255.255.252.0

$ cat file | awk -F'[: ]' '/inet addr/{print $3; exit}'
172.30.1.6

Upvotes: 2

Franck Might
Franck Might

Reputation: 71

Just use the command cut. 

ip a | grep -m1 "inet addr" | cut -d':' -f 2 | cut -d' ' -f 1

I also advise you to learn the use of other commands such as : wc,sed,tr,sort,uniq. They will help manipulate the output as you please. Here is a small lesson where we present you all these command : https://www.javatpoint.com/linux-filters

I hope to help you.

Upvotes: 1

souser
souser

Reputation: 6120

If all you want to do is obtain the ip address, there might be easier ways of achieving that using say hostname -i ( reference Which terminal command to get just IP address and nothing else? )

Since others have mentioned cut and awk, I will provide a solution using sed :

echo "inet addr:172.30.1.6  Bcast:172.30.140.255  Mask:255.255.252.0" | sed -e "s/.*\(addr:[^ ]*\) .*/\1/"

addr:172.30.1.6

echo "inet addr:172.30.1.6  Bcast:172.30.140.255  Mask:255.255.252.0" | sed -e "s/.*addr:\([^ ]*\) .*/\1/" 

172.30.1.6

Upvotes: 4

Matthew Fisher
Matthew Fisher

Reputation: 2336

Use cut with a delimiter

| cut -d':' -f 2 | cut -d' ' -f 1

Upvotes: 2

Tom Lubenow
Tom Lubenow

Reputation: 1161

Get out your scissors, it's cuttin' time.

echo inet addr:172.30.1.6  Bcast:172.30.140.255  Mask:255.255.252.0 | cut -d : -f 2 | cut -d " " -f 1

Upvotes: 5

Adam vonNieda
Adam vonNieda

Reputation: 1745

One way to do it ..

ifconfig | grep -m1 "inet addr" | awk '{print $2}' | awk -F: '{print $2}'

Upvotes: 4

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