clean /etc/hosts

Shell Programming and Scripting
1

hi all,
i need to write a script. it should be able to clean the /etc/hosts file like this:

first field is the ip (what else ;))
second field is the fqdn (full qualified domain name)
third field is the hostname

the fourth to n'th field is the rest.

i hope you understand what is needed?

tia,
DN2

btw. i use solaris to run the script. so there is no gawk only (n)awk!

2

so, there are ways to do this in perl ( open the file for writing ) and replace the respective strings using regexp.

3

What kind of cleaning do you want to do ?
Show us an example please.

Jean-Pierre.

4

o.k.:
the file looks like this:

192.168.0.100 hostname alias anotheralias hostname.mydomain.com

and should look like this

192.168.0.100 hostname.mydomain.com hostname alias anotheralias (and so on for every other alias)

5

The following awk program clean the /etc/hosts file :

#! /usr/bin/awk -f
NF>0 && $1 !~ /^#/ {

   comment    = "";
   ip         = $1;
   host_alias = "";
   fqdn       = "";

   if (match($0, /#/)) {
      comment = substr($0, RSTART);
      $0      = substr($0, 1, RSTART-1);
   }

   for (i=2; i<=NF; i++) {
      if ($i ~ /.*\..*\..*/)
         fqdn = (fqdn ? fqdn OFS : "") $i;
      else
         host_alias = (host_alias ? host_alias OFS : "") $i;
   }

   print ip, fqdn, host_alias, comment;
   next;
}
1

Input file :

#
# /etc/host
#

192.168.0.100 host0 alias0a alias0b host0.mydomain.com
192.168.0.101 host1 alias1a alias1b host1.mydomain.com # Comment for host1
192.168.0.102 host2.mydomain.com host2 alias2
192.168.0.103 host3.mydomain.com host3a hostb host3b.mydomain.com
192.168.0.104 host4
192.168.0.105 host5.mydomain.com

Output:

#
# /etc/host
#

192.168.0.100 host0.mydomain.com host0 alias0a alias0b 
192.168.0.101 host1.mydomain.com host1 alias1a alias1b # Comment for host1
192.168.0.102 host2.mydomain.com host2 alias2 
192.168.0.103 host3.mydomain.com host3b.mydomain.com host3a hostb 
192.168.0.104  host4 
192.168.0.105 host5.mydomain.com

Jean-Pierre.

6

wow, fantastic work.... thank you!