netmask in a script

[Dazed_75]

Yes Thomas.  If you look back a few messages in the thread, you will see
that not only was it suggested, but that is how I solved my need.  Thank you
though.

On Fri, Oct 28, 2011 at 1:28 PM, thomas at redhat.com <thomas at redhat.com>wrote:

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> Have you looked at ipcalc? It does some really cools stuff and can be
> scripted.
>
> On 10/27/2011 06:19 PM, Brian Cluff wrote:
> > I've never had a need to do any bit twiddling in bash... thanks for this
> > solution,  It was very educational.
> >
> > Brian Cluff
> >
> > On 10/27/2011 11:43 AM, Dale Farnsworth wrote:
> >> Larry wrote:
> >>> I would like to apply a netmask to an arbitrary IP in a bash/dash
> script
> >>> (e.g. apply 255.255.255.0 to 173.10.3.155 to get 173.10.3.0).  Is
> >>> there any
> >>> easy way to do that without taking the IP apart, doing 4 operations and
> >>> reassembling the results?
> >>
> >> I know you said without disassembly/reassembly, but here are some
> >> bash functions that apply the mask using disassembly/reassembly.
> >>
> >> ===================== begin =======================
> >> to_int()
> >> {
> >>     # Convert from dotted-quad to integer
> >>     local i=$1
> >>     local OIFS="$IFS"
> >>     IFS=.
> >>     i=($i)
> >>     IFS="$OIFS"
> >>     echo $(((${i[0]}<<  24) + (${i[1]}<<  16) + (${i[2]}<<  8) +
> >> ${i[3]}))
> >> }
> >>
> >> to_ip()
> >> {
> >>     # Covert from integer to dotted-quad
> >>     local d=$1
> >>     echo $(($d>>  24)).$(($d>>  16&  255)).$(($d>>  8&
>  255)).$(($d&255))
> >> }
> >>
> >> and_ip()
> >> {
> >>     # And two ip addresses in dotted-quad format
> >>     local ip1=$1
> >>     local ip2=$2
> >>     echo $(to_ip $(($(to_int $ip1)&  $(to_int $ip2))))
> >> }
> >> ===================== end =======================
> >>
> >> Just pass the ip and netmask to and_ip:
> >> Example:
> >>
> >> $ and_ip 11.22.33.44 255.255.255.0
> >> 11.22.33.0
> >>
> >> -Dale
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> >
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>
> - --
> Thomas Cameron, RHCA, RHCSS, RHCDS, RHCVA, RHCX
> Chief Architect, Canada and Central US
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-- 
Dazed_75 a.k.a. Larry

The spirit of resistance to government is so valuable on certain occasions,
that I wish it always to be kept alive.
  - Thomas Jefferson
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