Fistly, apologies for taking so long to summarize. Thanks to all who
replied.
My original question:
"Is there a program or function that takes as its arguments an ip
address
> and the mask and returns the subnet ?
>
> Eg. 160.100.100.50 255.255.255.0
>
> will return 160.100.100.0
>
> 197.34.183.34 255.255.255.224
>
> will return 197.34.183.32"
The simplest program I have is from Casper Dik. casper@holland.sun.com
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <netdb.h>
main(int argc, char **argv)
{
unsigned long addr, mask;
struct in_addr in;
if (argc != 3)
exit(1);
addr = inet_addr(argv[1]);
mask = inet_addr(argv[2]);
in.s_addr = addr & mask;
printf("addr %s w/ mask %s yields %s\n", argv[1], argv[2],
inet_ntoa(in));
}
For those who don't know, working out the Subnet is a logical bit AND.
Example:
194.80.80.2 mask 255.255.255.240
1100 0100 0101 0000 0101 0000 0000 0010
1111 1111 1111 1111 1111 1111 1111 1000
1100 0100 0101 0000 0101 0000 0000 0000
which is 194.80.80.0 as expected.
Thanks also to:
Mark `Hex' Hershberger
dengland@ivac.com
ravik@netcom.com
nick.leroy@norland.com
asola@inteliideas.com
fpardo@tisny.com
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