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/* ipmask.c
*
* Given argv[1] as a decimal netmask and argv[2] as a decimal IP address,
* print the resulting broadcast and network addresses to stdout. This is
* potentially useful in scripts which need the broadcast address and the
* network address but want to ask the user as few questions as possible.
*
* Copyright 1994 by David Niemi. Written in about 30 minutes on 13 Aug.
* The author places no restrictions on the use of this program, provided
* that this copyright is preserved in any derived source code.
*
* Typical compilation command for Linux:
* cc ipmask.c -Wall -O -m486 -N -o ipmask -s
*/
#define MYNAME "ipmask"
#include <stdio.h>
void Usage(void) {
fprintf (stderr,
"USAGE: %s <decimal netmask> <decimal IP address>\n",
MYNAME);
}
int main(int argc, char *argv[])
{
unsigned long netmask, ipaddr, netaddr, broadcast;
int in[4], j;
unsigned char bc[4],na[4];
if (3 != argc) {
Usage();
exit(1);
}
/* Check netmask */
if (4 != sscanf(argv[1],"%d.%d.%d.%d", &in[0],&in[1],&in[2],&in[3])) {
fprintf (stderr,"Invalid netmask \"%s\".\n", argv[1]);
Usage();
exit(1);
}
for (j=0; j<4; ++j) {
if (in[j]<0 || in[j]>255) {
fprintf (stderr,
"Invalid octet %d in netmask \"%s\".\n",
j+1, argv[1]);
Usage();
exit(1);
}
}
netmask = in[3] + 256 * (in[2] + 256 * (in[1] + 256 * in[0]));
/* Check IP address */
if (4 != sscanf(argv[2],"%d.%d.%d.%d", &in[0],&in[1],&in[2],&in[3])) {
fprintf (stderr,"Invalid IP address \"%s\".\n", argv[2]);
Usage();
exit(1);
}
for (j=0; j<4; ++j) {
if (in[j]<0 || in[j]>255) {
fprintf (stderr,
"Invalid octet %d in IP address \"%s\".\n",
j+1, argv[1]);
Usage();
exit(1);
}
}
ipaddr = in[3] + 256 * (in[2] + 256 * (in[1] + 256 * in[0]));
broadcast = ipaddr | (~ netmask);
bc[0] = broadcast / 256 / 256 / 256;
bc[1] = (broadcast / 256 / 256) % 256;
bc[2] = (broadcast / 256) % 256;
bc[3] = broadcast % 256;
netaddr = ipaddr & netmask;
na[0] = netaddr / 256 / 256 / 256;
na[1] = (netaddr / 256 / 256) % 256;
na[2] = (netaddr / 256) % 256;
na[3] = netaddr % 256;
printf ("%d.%d.%d.%d %d.%d.%d.%d\n",
bc[0], bc[1], bc[2], bc[3], na[0], na[1], na[2], na[3]);
exit(0);
}
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