From ilug-admin@linux.ie  Tue Aug  6 11:53:18 2002
Return-Path: <ilug-admin@linux.ie>
Delivered-To: yyyy@localhost.netnoteinc.com
Received: from localhost (localhost [127.0.0.1])
	by phobos.labs.netnoteinc.com (Postfix) with ESMTP id 1A320441E8
	for <jm@localhost>; Tue,  6 Aug 2002 06:48:22 -0400 (EDT)
Received: from phobos [127.0.0.1]
	by localhost with IMAP (fetchmail-5.9.0)
	for jm@localhost (single-drop); Tue, 06 Aug 2002 11:48:22 +0100 (IST)
Received: from lugh.tuatha.org (root@lugh.tuatha.org [194.125.145.45]) by
    dogma.slashnull.org (8.11.6/8.11.6) with ESMTP id g74BcHv26639 for
    <jm-ilug@jmason.org>; Sun, 4 Aug 2002 12:38:17 +0100
Received: from lugh (root@localhost [127.0.0.1]) by lugh.tuatha.org
    (8.9.3/8.9.3) with ESMTP id MAA18508; Sun, 4 Aug 2002 12:36:24 +0100
Received: from mel-rto2.wanadoo.fr (smtp-out-2.wanadoo.fr
    [193.252.19.254]) by lugh.tuatha.org (8.9.3/8.9.3) with ESMTP id MAA18475
    for <ilug@linux.ie>; Sun, 4 Aug 2002 12:36:18 +0100
X-Authentication-Warning: lugh.tuatha.org: Host smtp-out-2.wanadoo.fr
    [193.252.19.254] claimed to be mel-rto2.wanadoo.fr
Received: from mel-rta8.wanadoo.fr (193.252.19.79) by mel-rto2.wanadoo.fr
    (6.5.007) id 3D49FBEC000CB353 for ilug@linux.ie; Sun, 4 Aug 2002 13:35:46
    +0200
Received: from bolsh.wanadoo.fr (80.8.224.71) by mel-rta8.wanadoo.fr
    (6.5.007) id 3D49FF79000BE9E5 for ilug@linux.ie; Sun, 4 Aug 2002 13:35:46
    +0200
Received: from dave by bolsh.wanadoo.fr with local (Exim 3.32 #1 (Debian))
    id 17bJkP-0005ty-00 for <ilug@linux.ie>; Sun, 04 Aug 2002 13:40:33 +0200
Date: Sun, 4 Aug 2002 13:40:33 +0200
From: David Neary <dneary@wanadoo.fr>
To: ILUG <ilug@linux.ie>
Subject: Re: [ILUG] One Command -- Four Types
Message-Id: <20020804134033.A22333@wanadoo.fr>
References: <200208041036.g74AaBr31977@cdm01.deedsmiscentral.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-15
Content-Disposition: inline
In-Reply-To: <200208041036.g74AaBr31977@cdm01.deedsmiscentral.net>
User-Agent: Mutt/1.3.23i
Sender: ilug-admin@linux.ie
Errors-To: ilug-admin@linux.ie
X-Mailman-Version: 1.1
Precedence: bulk
List-Id: Irish Linux Users' Group <ilug.linux.ie>
X-Beenthere: ilug@linux.ie

SoloCDM wrote:
> How are there four (/bin/dnsdomainname /bin/domainname
> /bin/nisdomainname /bin/ypdomainname) different types of hostname
> links with their own separate options?

The program has different behaviour depending on the value of
argv[0], probably...

here's a simple example...

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

long int add(long int a, long int b)
{
  return a+b;
}

long int subtract(long int a, long int b)
{
  return a-b;
}

int main(int argc, char **argv)
{
  long int a, b; /* Operands */
  long int (*operation)(long int a, long int b);
  char *progname, *marker;

  if(argc != 3)
  {
    fprintf(stderr, "Usage: %s [int1] [int2]\n", argv[0]);
    exit(1);
  }

  progname = strrchr(argv[0], '/');
  if(progname == NULL)
    progname = argv[0];
  else
    progname ++; /* Skip past the '/' */
  
  if(strcmp(progname, "add") == 0)
  {
    operation = add;
  }
  else if (strcmp(progname, subtract) == 0)
  {
    operation = subtract;
  }
  else
  {
    fprintf(stderr, "Program called with invalid "
            "name %s. Quitting.\n", argv[0]);
    exit(1);
  }

  a = strtol(argv[1], &marker, 0); /* Use base 16 for args
                                    * starting 0x, and base 8 for 
                                    * args starting 0 */
  if(*marker != '\0')
  {
    fprintf(stderr, "Invalid character %c in argument %s.\n",
            *marker, argv[1]);
    exit(1);
  }

  b = strtol(argv[2], &marker, 0); /* Use base 16 for args
                                    * starting 0x, and base 8 for 
                                    * args starting 0 */
  if(*marker != '\0')
  {
    fprintf(stderr, "Invalid character %c in argument %s.\n",
            *marker, argv[2]);
    exit(1);
  }
  
  printf("%ld %c %ld = %ld\n", 
          a, 
          (operation == add)?'+':'-', 
          b, 
          operation(a, b));
          
  return 0;
}

Say that's in operation.c, compile it using 

gcc -ansi -pedantic -Wall -W -O2 -o add operation.c
and then 
ln add subtract
and run both, with appropriate arguments.



-- 
       David Neary,
    Marseille, France
  E-Mail: bolsh@gimp.org

-- 
Irish Linux Users' Group: ilug@linux.ie
http://www.linux.ie/mailman/listinfo/ilug for (un)subscription information.
List maintainer: listmaster@linux.ie


