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sed -e '/\([0-9]\{1,3\}[.]\)\{3\}[0-9]\{1,3\}/R hosts' dhcpd.conf

So far, this appends a single line from hosts to the matched line in
dhcpd.conf, here is sample output:

        fixed-address         192.168.1.81;
192.168.1.92    term012

The first line is from dhcpd.conf and the second is from hosts.
However, I have not been able to figure out how to append the
appropriate line; at the moment, it's going in sequence through hosts
and the lines being appended do not match the IP.

I've tried to get the output of grep piped into the read file, a la:

sed -e '/\([0-9]\{1,3\}[.]\)\{3\}[0-9]\{1,3\}/R `grep \1 hosts`'
dhcpd.conf

But it does nothing. I've tried several variants to no avail.

1) So the first task is to get the proper lines appended to the proper
places.

2) The second task is to modify the new data to have only the host
name.
To the best of my knowledge, reading does not affect the pattern space.
Is it possible to accomplish this in one pass if the pattern space is
not affected? Will I have to write the output to a new file and then
sed it again to get the results I want?

Any and all help is appreciated.

TIA,
Al

You can use sed for both of these. (untested)

sed -n 's/^\([0-9][0-9.]*\)[\t ]*\([^ \t]*\).*/s:\\<\1\\>:\2:p' hosts >t

sed -f t dhcpd.conf

(This assumes your sed knows about \< and \> for matching word boundaries)

Gnu sed has a '-i' option to do "in place" editing, but it would be more
normal to write the output of sed to a new file and then move that into
the original place.

 > Hi all,
 >   I'm trying to take a dhcpd.conf file and replace each IP address in
 > it with a host name. The address-to-hostname map is in hosts. This is
 > what I've got so far:
 >
 > sed -e '/\([0-9]\{1,3\}[.]\)\{3\}[0-9]\{1,3\}/R hosts' dhcpd.conf
 >
 > So far, this appends a single line from hosts to the matched line in
 > dhcpd.conf, here is sample output:
 >
 >         fixed-address         192.168.1.81;
 > 192.168.1.92    term012
 >
 > The first line is from dhcpd.conf and the second is from hosts.
 > However, I have not been able to figure out how to append the
 > appropriate line; at the moment, it's going in sequence through hosts
 > and the lines being appended do not match the IP.
 >
 > I've tried to get the output of grep piped into the read file, a la:
 >
 > sed -e '/\([0-9]\{1,3\}[.]\)\{3\}[0-9]\{1,3\}/R `grep \1 hosts`'
 > dhcpd.conf
 >
 > But it does nothing. I've tried several variants to no avail.
 >
 > 1) So the first task is to get the proper lines appended to the proper
 > places.
 >
 > 2) The second task is to modify the new data to have only the host
 > name.
 > To the best of my knowledge, reading does not affect the pattern space.
 > Is it possible to accomplish this in one pass if the pattern space is
 > not affected? Will I have to write the output to a new file and then
 > sed it again to get the results I want?
 >
 > Any and all help is appreciated.

Can you use awk instead of sed? It's made for this kind of job. For
example, if dhcp.conf contains:

    fixed-address         192.168.1.81;

and "hosts" contains:

    192.168.1.81    term012

Then this:

    awk 'NR==FNR{map[$1";"]=$2";";next}{$2=map[$2]}1' hosts dhcpd.conf

will produce this:

    fixed-address term012;

Regards,

        Ed.

Quote:>     awk 'NR==FNR{map[$1";"]=$2";";next}{$2=map[$2]}1' hosts dhcpd.conf

  awk 'NR==FNR{map[$1";"]=$2";";next}$2 in map{$2=map[$2]}1' hosts
dhcpd.conf

Best,
Xicheng

Quote:> will produce this:

>     fixed-address term012;

> Regards,

>    Ed.