well, an IP4 address is just an unsigned int32, and a netmask is just the number of bits to keep...
you could turn the dotted notation into an int32, then mask off the proper bits, then translate back to the dotted notation.

Or you could use Python for the script and use the ip address library in Python[1] to apply the netmask.

[1] http://code.google.com/p/ipaddr-py/

On 10/26/2011 09:49 PM, Dazed_75 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?
> 
> 
> 
> 
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