There are 2 programs in here.... 
Here is a program to convert your hosts.net to domain.txt:

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#include <stdio.h>
#include <ctype.h>
#include <string.h>

#define LINELEN 256
/* copyright 1989 - John D. Hays, KD7UW */
main(int argc,char *argv[])
{

	FILE *fi,*fo;
	char string[LINELEN-1];
	char addr[20],hname1[80],hname2[80];
	char *x,*y,*z;
	int cnt;

	fprintf(stderr,"COPYRIGHT 1989 - John D. Hays, KD7UW\n");
	if (argc != 3) 
	{
	fprintf(stderr,"Usage: %s input-hosts.net output-domain.txt\n\007",
		argv[0]);
	exit(0);
	}

	if ((fi=fopen(argv[1],"r")) != NULL)
	{
		fo = fopen(argv[2],"w");
		while (fgets(string,LINELEN,fi) != NULL)
		{
			
			y = strchr(string,'\n');
			*y = '\0';
			addr[0] = '\0';
			hname1[0] = '\0';
			hname2[0] = '\0';

			if ((string[0] == '#') || (strlen(string) < 3))
			{
			fprintf(fo,"%s\n",string);
			goto foo;
			}
			y = strchr(string,'#');
			if (y != NULL) 
			{
			fprintf(fo,"#%s\n",y);
			*y = '\0';
			}
			sscanf(string,"%s%s%s",addr,hname1,hname2);
			if (strchr(hname1,'.'))
			{
			x = hname1;
			z = hname2;
			}
			else
			{
			x = hname2;
			z = hname1;
			}
			if ((*x == '\0') || (*z == '\0'))
			{
			fprintf(fo,"%s.\tIN\tA\t%s\n",hname1,addr);
			}
			else
			{
			fprintf(fo,"%s.\tIN\tA\t%s\n",x,addr);
			fprintf(fo,"%s.\tIN\tCNAME\t%s.\n",z,x);
			}
foo:      		fprintf(stderr,"%s\n",string);
		}
	}
}
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This program allows you to push mail destined for one host
to another (i.e. going on vacation and shutting down your
host but want your mail delivered by your "buddy"):

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#include <stdio.h>
#include <dir.h>
#include <dos.h>
#include <fcntl.h>
#include <string.h>
#define MAXLINE 256

main(int argc,char *argv[])
{
	struct ffblk block;
	int done,i;
	FILE *fd,*fo;
	char *j,str[MAXLINE+2],*strp;
	
	fprintf(stderr,"\n%s is COPYRIGHT 1989 by John D. Hays (KD7UW)\n",argv[0]);
	fprintf(stderr,"Authorized for unlimited distribution for ");
	fprintf(stderr,"Amateur Radio Use\n");
	fprintf(stderr,"This notice must be retained.  All Rights Reserved.\n\n");
	if (argc < 3)
	{
		fprintf(stderr,"Usage: %s oldhost forwardhost \007\n",argv[0]);
		exit(0);
	}
	
	done = findfirst("*.wrk",&block,0x3F);

	while (!done) {
		if ((fd = fopen(block.ff_name,"r")) != NULL)
		strp = str; /* Turbo-C is not handling fgets right ??? */
		{
			strp = fgets(strp,MAXLINE,fd);
			j = strrchr(strp,'\n');
			if (j != NULL) *j = '\0';
			if (stricmp(argv[1],strp) == 0)
			{
				fprintf(stderr,"Changing: %s\n",block.ff_name);
				i = unlink(block.ff_name);
				fo = fopen(block.ff_name,"w");
				fprintf(fo,"%s\n",argv[2]);
				while ((strp = fgets(strp,MAXLINE,fd)) != NULL)
				{
					fprintf(fo,"%s",strp);
				}
			}
			fclose(fd);
			fclose(fo);
		}
		fprintf("%s: Unable to open %s\n",argv[0],block.ff_name);
		done = findnext(&block);
	}
}
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Hope these help those of you who are bringing up NOS.

John D. Hays KD7UW
hays@apollo.hp.com