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Full Discussion: Using Sed to remove part of line with regex
Top Forums Shell Programming and Scripting Using Sed to remove part of line with regex Post 302461087 by msarro on Friday 8th of October 2010 12:28:33 PM
Old 10-08-2010
Using Sed to remove part of line with regex
Greetings everyone. Right now I am working on a script to be used during automated deployment of servers. What I have to do is remove localhost.localdomain and localhost6.localdomain6 from the /etc/hosts file. Simple, right? Except most of the examples I've found using sed want to delete the entire line.
Here's the example contents of the file:
Code:
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1               localhost.localdomain localhost
::1             localhost6.localdomain6 localhost6
172.30.0.133  loghost

Here's the regex I was planning to use:
Code:
 /\bl.*(n|n6)\b/g

I tested it and it looks like its working. Now I just have to figure out how to use it in sed. The file needs to be left in place, so I know it'll be starting something along these lines...
sed -i (delete) /\bl.*(n|n6)\b/g /etc/hosts

Any help would be very much appreciated; I'm still getting used to using sed and 90% of the examples still look completely cryptic to me.

My ultimate goal is to have the /etc/hosts file look like this:
Code:
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1               localhost
::1             localhost6
172.30.0.133  loghost

 

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LEARN ABOUT CENTOS

unbound-streamtcp

unbound-streamtcp(1)						      unbound						      unbound-streamtcp(1)

NAME

       unbound-streamtcp - unbound DNS lookup utility

SYNOPSIS

       unbound-streamtcp [-unsh] [-f ipaddr[@port]] name type class

DESCRIPTION

       unbound-streamtcp sends a DNS Query of the given type and class for the given name to the DNS server over TCP and displays the response.

       If  the	server to query is not given using the -f option then localhost (127.0.0.1) is used. More queries can be given on one commandline,
       they are resolved in sequence.

       The available options are:

       name   This name is resolved (looked up in the DNS).

       type   Specify the type of data to lookup.

       class  Specify the class to lookup for.

       -u     Use UDP instead of TCP. No retries are attempted.

       -n     Do not wait for the answer.

       -s     Use SSL.

       -h     Print program usage.

       -f ipaddr[@port]
	      Specify the server to send the queries to. If not specified localhost (127.0.0.1) is used.

EXAMPLES

       Some examples of use.

       $ unbound-streamtcp www.example.com A IN

       $ unbound-streamtcp -f 192.168.1.1 www.example.com SOA IN

       $ unbound-streamtcp -f 192.168.1.1@1234 153.1.168.192.in-addr.arpa. PTR IN

EXIT CODE

       The unbound-streamtcp program exits with status code 1 on error, 0 on no error.

AUTHOR

       This manual page was written by Tomas Hozza <thozza@redhat.com>.

NLnet Labs							   Mar 21, 2013 					      unbound-streamtcp(1)
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