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From: jky@neptune.dsc.com (Jacob Kan Yu)
Newsgroups: comp.unix.questions
Subject: Re: Starting a daemon on a SVR3
Message-ID: <1752@dschub.dsc.com>
Date: 2 Jan 91 21:36:03 GMT
References: <25360@adm.brl.mil>
Sender: news@dschub.dsc.com
Lines: 54

wolf@grasp1.univ-lyon1.fr writes:

>On an old AIX, I use following code to start a daemon (which does not run
>with root privileges).

>   setbuf(stdout,NULL); printf("Listserv v0.99: daemon started\n\r");
>   if (fork()) exit (0);   /* Dissociate us from tty */
>   for (i=getdtablesize()-1; i>=0; i--)
>      (void)close(i);
>   (void)open("/",0);
>   (void)dup2(0,1);
>   (void)dup2(0,2);
>   i=open("/dev/tty",2);
>   if (i>=0) {
>      ioctl(i,TIOCNOTTY,(char *)0);
>      (void)close(i);
>   }

>This works fine, but I get trouble when porting this daemon to an SRV3.
>getdtablesize does not exist anymore, so I close all open files manually
>with a fixed loop (I put 4 in first index).

What's about this:

    for ( i = 0 ; i < NOFILE ; i++ )
	close( i );

The problem I have is that "NOFILE" is 20 for System V/386 Release 3.0 and is
60 for Release 3.2 and the comments in "<sys/param.h>" says this number is
no longer a constant and should be removed in the next release.  Anybody
have better idea?

>The ioctl call does also not exist, and I found no equivalence.
>After having executed the new code it loads itself in background and
>ps shows me it does not depend anymore on a tty.  Despite this, when
>I loggoff, the process is being killed.  Can anyone explain me what I
>have to do to start properly a daemon?  Thanx.

I am not sure about this ioctl call but you probably should have your
program to ignore "SIGHUP" signal.

>-- 
>Christophe Wolfhugel                  |  Email: wolf@grasp1.univ-lyon1.fr
>INSA Lyon - Departement Informatique  |  Fax: (+33) 72 44 08 00 
>69621 Villeurbanne Cedex, France      |    (Attn-To: Wolfhugel - C 210)

Jacob Yu 	Internet: jky%neptune%dschub@hub.ucsb.edu
		Uucp:     pyramid!ucsbcsl!dschub!neptune!jky

Life is but a walking shadow.

>  Disclaimer: these are my own opinions, not my employer's.

Yes, these are my own opinions too.