From mboxrd@z Thu Jan 1 00:00:00 1970 From: "John T. Williams" Subject: Re: Switching between foreground and background Date: Tue, 23 Sep 2003 12:07:24 -0400 Sender: linux-c-programming-owner@vger.kernel.org Message-ID: <003e01c381ec$c76473a0$ed64a8c0@descartes> References: <20030922104825.81134.qmail@web20002.mail.yahoo.com> <003501c3811f$610395a0$ed64a8c0@descartes> <3F702813.8030200@gsecone.com> Reply-To: "John T. Williams" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: List-Id: Content-Type: text/plain; charset="us-ascii" To: rvk@gsecone.com, "John T. Williams" Cc: Silambu Chelvan , linux-newbie@vger.kernel.org, linux-c-programming@vger.kernel.org I have to admit that I don't know why, but every resource I've ever read about causing programs to gain daemon behavior has involved forking 2 times and then starting the program code. If anyone here does know why, I'd would be happy to hear it. ----- Original Message ----- From: "Raghuveer" To: "John T. Williams" Cc: "Silambu Chelvan" ; Sent: Tuesday, September 23, 2003 7:01 AM Subject: Re: Switching between foreground and background > John T. Williams wrote: > > >I think part of the problem here might be conceptual. > > > >If I understand what you want, you'd like, on a signal, for your program to > >go into the background (still running but no longer blocking the terminal > >input/output). On another signal you would like the program to come back to > >the foreground. > > > >If this is the case, the problem you're facing is that the program being in > >the foreground and the background is actually part of the shell, not a > >property of the program running. Most Shells provide a way to switch > >programs from the foreground to the background and back. > >BASH for example I could type > > > >$>./myprogram > >(cntr + Z) //suspends the current program and prings the prompt back > >$>bg (runs the program in the background) > > > >The only way that I know of to force a program to run in the background in > >the code is to make it a daemon which is done by forking twice > > > >int main( ) { > > if(fork()==0) { > > if( fork() == 0 ) { > > program code starts here > > } > > exit(0); > > } > > exit(0); > >} > > > > > I don't feel it's required to fork() twice for making it a daemon, once > is enough. Ya, but should use setpgrp() or setpid() and close stdin, out > and err after the fork and go to infinite loop. > > -Raghu > > > > >----- Original Message ----- > >From: "Silambu Chelvan" > >To: > >Sent: Monday, September 22, 2003 6:48 AM > >Subject: Switching between foreground and background > > > > > > > > > >>Hi all, > >> > >>I have written some program with signal handler. Is > >>this possible, if > >>one of the signals registered with my program is > >>raised, my program > >>should goto background and should come to foreground > >>when some other of the > >>registered signal is raised. how to do it? > >> > >>Any function available to switch a process between > >>foreground and > >>background at runtime? > >> > >>with regards, > >>M. SilambuChelvan > >> > >> > >>__________________________________ > >>Do you Yahoo!? > >>Yahoo! SiteBuilder - Free, easy-to-use web site design software > >>http://sitebuilder.yahoo.com > >>- > >>To unsubscribe from this list: send the line "unsubscribe linux-newbie" in > >>the body of a message to majordomo@vger.kernel.org > >>More majordomo info at http://vger.kernel.org/majordomo-info.html > >>Please read the FAQ at http://www.linux-learn.org/faqs > >> > >> > > > >- > >To unsubscribe from this list: send the line "unsubscribe linux-newbie" in > >the body of a message to majordomo@vger.kernel.org > >More majordomo info at http://vger.kernel.org/majordomo-info.html > >Please read the FAQ at http://www.linux-learn.org/faqs > > > > > > > > > - > To unsubscribe from this list: send the line "unsubscribe linux-newbie" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.linux-learn.org/faqs